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Flashtube

A flashtube (flashlamp) is an electric arc lamp designed to produce extremely intense, incoherent, full-spectrum white light for a very short time. A flashtube is a glass tube with an electrode at each end and is filled with a gas that, when triggered, ionizes and conducts a high-voltage pulse to make light. Flashtubes are used most in photography; they also are used in science, medicine, industry, and entertainment.

Construction

The lamp comprises a hermetically sealed glass tube, which is filled with a noble gas, usually xenon, and electrodes to carry electric current to the gas. Additionally, a high voltage power source is necessary to energize the gas as a trigger event. A charged capacitor is usually used to supply energy for the flash, so as to allow very speedy delivery of very high electrical current when the lamp is triggered.

Glass envelopes
The glass envelope is most commonly a thin tube, often made of fused quartz, borosilicate or Pyrex, which may be straight, or bent into a number of different shapes, including helical, "U" shape, and circular (to surround a camera lens for shadowless photography—'ring flashes'). In some applications, the emission of ultraviolet light is undesired, whether due to production of ozone, damage to laser rods, degradation of plastics, or other detrimental effects. In these cases, a doped fused silica is used. Doping with titanium dioxide can provide different cutoff wavelengths on the ultraviolet side, but the material suffers from solarization; it is often used in medical and sun-ray lamps and some non-laser lamps. A better alternative is a cerium-doped quartz; it does not suffer from solarization and has higher efficiency, as part of the absorbed ultraviolet is reradiated as visible via fluorescence. Its cutoff is at about 380 nm. Conversely, when ultraviolet is called for, a synthetic quartz is used as the envelope; it is the most expensive of the materials, but it is not susceptible to solarization and its cutoff is at 160 nm.

The power level of the lamps is rated in watts/area, total electrical input power divided by the lamp's inner wall surface. Cooling of the electrodes and the lamp envelope is of high importance at high power levels. Air cooling is sufficient for lower average power levels. High power lamps are cooled with a liquid, typically by flowing deionized water through a tube in which the lamp is encased. Water-cooled lamps will generally have the glass shrunk around the electrodes, to provide a direct thermal conductor between them and the cooling water. The cooling medium should flow also across the entire length of the lamp and electrodes. High average power or continuous-wave arc lamps must have the water flow across the ends of the lamp, and across the exposed ends of the electrodes as well, so the deionized water is used to prevent a short circuit. Above 15 W/cm2 forced air cooling is required; liquid cooling if in a confined space. Liquid cooling is generally necessary above 30 W/cm2.

Thinner walls can survive higher average-power loads due to lower mechanical strain across the thickness of the material, which is caused by a temperature gradient between the hot plasma and cooling water, (e.g. 1 mm thick doped quartz has a limit of 160 W/cm2, a 0.5 mm thick one has a limit of 320 W/cm2). For this reason, thinner glass is often used for continuous-wave arc-lamps. Thicker materials can generally handle more impact energy from the shock wave that a short-pulsed arc can generate, so quartz as much as 1 mm thick is often used in the construction of flashtubes. The material of the envelope provides another limit for the output power; 1 mm thick fused quartz has a limit of 200 W/cm2, synthetic quartz of same thickness can run up to 240 W/cm2. Other glasses such as borosilicate generally have less than half the power loading capacity of quartz. Aging lamps require some derating, due to increased energy absorption in the glass due to solarization and sputtered deposits.

Electrodes and seals
The electrodes protrude into each end of the tube, and are sealed to the glass using a few different methods. "Ribbon seals" use thin strips of molybdenum foil bonded directly to the glass, which are very durable, but are limited in the amount of current that can pass through. "Solder seals" bond the glass to the electrode with a solder for a very strong mechanical seal, but are limited to low temperature operation. Most common in laser pumping applications is the "rod seal", where the rod of the electrode is wetted with another type of glass and then bonded directly to a quartz tube. This seal is very durable and capable of withstanding very high temperature and currents. The seal and the glass must have the same coefficient of thermal expansion.

For low electrode wear the electrodes are usually made of tungsten, which has the highest melting point of any metal, to handle the thermionic emission of electrons. Cathodes are often made from porous tungsten filled with a barium compound, which gives low work function; the structure of cathode has to be tailored for the application. Anodes are usually made from pure tungsten, or, when good machinability is required, lanthanum-alloyed tungsten, and are often machined to provide extra surface area to cope with power loading. DC arc lamps often have a cathode with a sharp tip, to help keep the arc away from the glass and to control temperature. Flashtubes usually have a cathode with a flattened radius, to reduce the incidence of hot spots and decrease sputter caused by peak currents, which may be in excess of 1000 amperes. Electrode design is also influenced by the average power. At high levels of average power, care has to be taken to achieve sufficient cooling of the electrodes. While anode temperature is of lower importance, overheating the cathode can greatly reduce the lamp's life expectancy.

Gases and fill pressure
Depending on the size, type, and application of the flashtube, gas fill pressures may range from a few kilopascals to hundreds of kilopascals (0.01–4.0 atmospheres or tens to thousands of torr). Generally, the higher the pressure, the greater the output efficiency. Xenon is used mostly because of its good efficiency, converting nearly 50% of electrical energy into light. Krypton, on the other hand, is only about 40% efficient, but at low currents is a better match to the absorption spectrum of YAG lasers. A major factor affecting efficiency is the amount of gas behind the electrodes, or the "dead volume". A higher dead volume leads to a lower pressure increase during operation.

Operation
The electrodes of the lamp are usually connected to a capacitor, which is charged to a relatively high voltage (generally between 250 and 5000 volts), using a step up transformer and a rectifier. The gas, however, exhibits extremely high resistance, and the lamp will not conduct electricity until the gas is ionized. Once ionized, or "triggered", a spark will form between the electrodes, allowing the capacitor   to discharge. The sudden surge of electric current quickly heats the gas to a plasma state, where electrical resistance becomes very low. There are several methods of triggering.

External triggering

External triggering is the most common method of operation, especially for photographic use. The electrodes are charged to a voltage high enough to respond to triggering, but below the lamp's self-flash threshold. An extremely high voltage pulse, (usually between 2000 and 150,000 volts), the "trigger pulse", is applied either directly to or very near the glass envelope. (Water-cooled flashtubes sometimes apply this pulse directly to the cooling water, and often to the housing of the unit as well, so care must be taken with this type of system.) The short, high voltage pulse creates a rising electrostatic field, which ionizes the gas inside the tube. The capacitance of the glass couples the trigger pulse into the envelope, where it exceeds the breakdown voltage of the gas surrounding one or both of the electrodes, forming spark streamers. The streamers propagate via capacitance along the glass at a speed of 1 centimeter in 60 nanoseconds (170 km/s). (A trigger pulse must have a long enough duration to allow one streamer to reach the opposite electrode, or erratic triggering will result.) The triggering can be enhanced by applying the trigger pulse to a "reference plane", which may be in the form of a metal band or reflector affixed to the glass, a conductive paint, or a thin wire wrapped around the length of the lamp. If the capacitor voltage is greater than the voltage drop between the cathode and the anode, when the internal spark streamers bridge the electrodes the capacitor will discharge through the ionized gas, heating the xenon to a high enough temperature for the emission light.

Series triggering

Series triggering is more common in high powered, water-cooled flashtubes, such as those found in lasers. The high-voltage leads of the trigger-transformer are connected to the flashtube in series, (one lead to an electrode and the other to the capacitor), so that the flash travels through both the transformer and the lamp. The trigger pulse forms a spark inside the lamp, without exposing the trigger voltage to the outside of the lamp. The advantages are better insulation, more reliable triggering, and an arc that tends to develop well away from the glass, but at a much higher cost. The series-triggering transformer also acts as an inductor. This helps to control the flash duration, but prevents the circuit from being used in very fast discharge applications. The triggering can generally take place with a lower voltage at the capacitor than is required for external triggering. However, the trigger-transformer becomes part of the flash circuit, and couples the triggering-circuit to the flash energy. Therefore, because the trigger-transformer has very low impedance, the transformer, triggering-circuit, and silicon controlled rectifier (SCR) must be able to handle very high peak-currents, often in excess of 1500 amps.

Simmer-voltage triggering

Simmer-voltage triggering is the least common method. In this technique, the capacitor voltage is not initially applied to the electrodes, but instead, a high voltage spark streamer is maintained between the electrodes. The high current from the capacitor is delivered to the electrodes using a thyristor or a spark gap. This type of triggering is used mainly in very fast rise time systems, typically those that discharge in the microsecond regime, such as used in high-speed, stop-motion photography or dye lasers. The simmering spark-streamer causes the arc to develop in the exact center of the lamp, increasing the lifetime dramatically. If external triggering is used for extremely short pulses, the spark streamers may still be in contact with the glass when the full current-load passes through the tube, causing wall ablation, or in extreme cases, cracking or even explosion of the lamp. However, because very short pulses often call for very high voltage and low capacitance, to keep the current density from rising too high, some microsecond flashtubes are triggered by simply "over-volting", that is, by applying a voltage to the electrodes which is much higher than the lamp's self-flash threshold, using a spark gap. Often, a combination of simmer voltage and over-volting is used.

Prepulse techniques
Very rapid rise-times are often achieved using a prepulse technique. This method is performed by delivering a small flash through the lamp just before the main flash. This flash is of much lower energy than the main flash (typically less than 10%) and, depending on the pulse duration, is delivered just a few thousandths to a few millionths of a second before the main flash. The prepulse heats the gas, producing a dim, short-lived afterglow that results from free electrons and ionized particles that remain after the pulse shuts down. If the main flash is initiated before these particles can recombine, this provides a good quantity of ionized particles to be used by the main flash. This greatly decreases the rise time. It also reduces the shock wave and makes less noise during operation, vastly increasing the lifetime of the lamp. It is especially effective on very fast-discharge applications, allowing the arc to expand faster and better fill the tube. It is very often used with simmer voltage and sometimes with series triggering, but rarely used with external triggering. Prepulse techniques are most commonly used in the pumping of dye lasers, greatly increasing the conversion efficiency. However, it has also been shown to increase the efficiency of other lasers with longer fluorescence lifetimes (allowing longer pulses), such as Nd:YAG or titanium sapphire, by creating pulses with almost square waveforms.

Ablative flashtubes
Ablative flashtubes are triggered by under-pressurizing. Ablative flashtubes are typically constructed using quartz tubing and one or both electrodes hollowed out, allowing a vacuum pump to be attached to control the gas pressure. The electrodes of the lamp are connected to a charged capacitor, and then the gas is vacuumed from the lamp. When the gas reaches a low enough pressure (often just a few torr) randomly-ionized particles are able to accelerate to velocities sufficient to begin ejecting electrons from the cathode as they impact its surface, resulting in a Townsend avalanche that causes the lamp to self-flash. At such low pressures, the efficiency of the flash would normally be very low. However, because of the low pressure, the particles have room to accelerate to very high speeds, and the magnetic forces expand the arc so that the bulk of its plasma becomes concentrated at the surface, bombarding the glass. The bombardment ablates (vaporizes) large amounts of quartz from the inner wall. This ablation creates a sudden, violent, localized increase in the internal pressure of the lamp, increasing the efficiency of the flash to very high levels. The ablation, however, causes extensive wear to the lamp, weakening the glass, and they typically need replacement after a very short lifetime.

Ablative flashtubes need to be refilled and vacuumed to the proper pressure for each flash. Therefore, they cannot be used for very high-repetition applications. Also, this usually precludes the use of very expensive gases like krypton or xenon. The most common gas used in an ablative flashtube is air, although sometimes cheap argon is also used. The flash usually must be very short to prevent too much heat from transferring to the glass. However, because nearly all the plasma is concentrated at the surface, the lamps have very low inductance and flashes can often be shorter than a normal lamp of comparative size. The flash from a single ablative flashtube can also be more intense than multiple lamps. For these reasons, the most common use for the lamps is for the pumping of dye lasers.

Variable pulse width control
In addition, an insulated-gate bipolar transistor (IGBT) can be connected in series with both the trigger transformer and the lamp, making adjustable flash durations possible. An IGBT used for this purpose must be rated for a high pulsed-current, so as to avoid over-current damage to the semiconductor junction. This type of system is used frequently in high average-power laser systems, and can produce pulses ranging from 500 microseconds to over 20 milliseconds. It can be used with any of the triggering techniques, like external and series, and can produce square wave pulses. It can even be used with simmer voltage to produce a "modulated" continuous wave output, with repetition rates over 300 hertz. With the proper large bore, water-cooled flashtube, several kilowatts of average-power output can be obtained.

Electrical requirements
The electrical requirements for a flashtube can vary, depending on the desired results. The usual method is to first determine the pulse duration, the maximum amount of energy tolerable at that duration (explosion energy), and the safe amount of operating energy. Then pick a current density that will emit the desired spectrum, and let the lamp's resistance determine the necessary combination of voltage and capacitance to produce it. The resistance in flashtubes varies greatly, depending on pressure, shape, dead volume, current density, time, and flash duration, and therefore, is usually referred to as impedance. The most common symbol used for lamp impedance is Ko, which is expressed as ohms per the square root of amps (ohms(amps0.5).

Ko is used to calculate the amount of input voltage and capacitance needed to emit a desired spectrum, by controlling the current density. Ko is determined by the internal diameter, arc length, and gas type of the lamp and, to a lesser extent, by fill pressure. The resistance in flashtubes is not constant, but quickly drops as current density increases. In 1965, John H. Goncz showed that the plasma resistivity in flashtubes is inversely proportional to the square root of current density. As the arc develops, the lamp experiences a period of negative resistance, causing both the resistance and voltage to decrease as the current increases. This occurs until the plasma comes into contact with the inner wall. When this happens, the voltage becomes proportional to the square root of current, and the resistance in the plasma becomes stable for the remainder of the flash. It is this value which is defined as Ko. However, as the arc develops the gas expands, and calculations for Ko do not take into account the dead volume, which leads to a lower pressure increase. Therefore, any calculation of Ko is merely an approximation of lamp impedance.

Xenon
As with all ionized gases, xenon flashtubes emit light in various spectral lines. This is the same phenomenon that gives neon signs their characteristic color. However, neon signs emit red light because of extremely low current-densities when compared to those seen in flashtubes, which favors spectral lines of longer wavelengths. Higher current-densities tend to favor shorter wavelengths. The light from xenon, in a neon sign, likewise is rather violet.

The spectrum emitted by flashtubes is far more dependent on current density than on the fill pressure or gas type. Low current-densities produce narrow spectral-line emission, against a faint background of continuous radiation. Xenon has many spectral lines in the UV, blue, green, red, and IR portions of the spectrum. Low current densities produce a greenish-blue flash, indicating the absence of significant yellow or orange lines. At low current-densities, most of xenon's output will be directed into the invisible IR spectral lines around 820, 900, and 1000 nm. Low current-densities for flashtubes are generally less than 1000 A/cm2.

Higher current-densities begin to produce continuum emission. Spectral lines broaden and become less dominant as light is produced across the spectrum, usually peaking, or "centered", on a certain wavelength. Optimum output-efficiency in the visual range is obtained at a density that favors "greybody radiation" (an arc that produces mostly continuum emission, but is still mostly translucent to its own light; an effect similar to sunlight when it passes through a cloud). For xenon, greybody radiation is centered near green, and produces the right combination for white light. Greybody radiation is produced at densities above 2400 A/cm2.

Current densities that are very high, approaching 4000 A/cm2, tend to favor black-body radiation. Spectral lines all but disappear as the continuum radiation dominates, and output center shifts toward the ultraviolet. As current densities become even higher, visually, xenon's output spectrum will begin to settle on that of a blackbody radiator with a color temperature of 9800 kelvins (a rather sky-blue shade of white). Except in cases where intense UV light is needed, such as water decontamination, blackbody radiation is usually not desired because the arc becomes opaque, and much of the radiation from within the arc can be absorbed before reaching the surface, impairing output efficiency.

Due to its high-efficiency, white output, xenon is used extensively for photographic applications, despite its great expense. In lasers, spectral-line emission is usually favored, as these lines tend to better match absorption lines of the lasing media. Krypton is also occasionally used. At low current-densities, krypton's spectral-line output in the near-IR range is better matched to the absorption profile of neodymium-based laser media than xenon emission, and very closely matches the narrow absorption-profile of Nd:YAG. None of xenon's spectral lines match Nd:YAG's absorption lines so, when pumping Nd:YAG with xenon, the continuum radiation must be used.

Krypton and other gases

All gases produce spectral lines which are specific to the gas, superimposed on a background of continuum radiation. With all gases, low current-densities produce mostly spectral lines, with the highest output being concentrated in the near-IR between 650 and 1000 nm. Krypton's strongest peaks are around 760 and 810 nm. Argon has many strong peaks at 670, 710, 760, 820, 860, and 920 nm. Neon has peaks around 650, 700, 850, and 880 nm. As current densities become higher, the output of continuum radiation will increase more than the spectral-line radiation at a rate 20% greater, and output center will shift toward the visual spectrum. At greybody current-densities there is only a slight difference in the spectrum emitted by various gases. At very high current-densities, all gases will begin to operate as blackbody radiators, with spectral outputs resembling a blue giant star, centered in the UV.

Heavier gases exhibit higher resistance, and therefore, have a higher value for Ko. Impedance, being defined as the resistance required to change energy into work, is higher for heavier gases, and as such, the heavier gases are much more efficient than the lighter ones. Helium and neon are far too light to produce an efficient flash. Krypton can be as good as 40% efficient, but requires up to a 70% increase in pressure over xenon to achieve this. Argon can be up to 30% efficient, but requires an even greater pressure-increase. At such high pressures, the voltage drop between the electrodes, formed by the spark streamer, may be greater than the capacitor voltage. These lamps often need a "boost voltage" during the trigger phase, to overcome the extremely high trigger-impedance.

Nitrogen, in the form of air, has been used in flashtubes in home made dye lasers, but the nitrogen and oxygen present form chemical reactions with the electrodes, and themselves, causing premature wear and the need to adjust the pressure for each flash.

Some research has been done on mixing gases to alter the spectral output. The effect on the output spectrum is negligible, but the effect on efficiency is great. Adding a lighter gas will only reduce the efficiency of the heavier one.

Light production

As the current pulse travels through the tube, it ionizes the atoms, causing them to jump to higher energy-levels. Three types of particles are found within the arc plasma, consisting of electrons, positively ionized atoms, and neutral atoms. At any given time during the flash, the ionized atoms make up less than 1% of the plasma and produce all of the emitted light. As they recombine with their lost electrons they immediately drop back to a lower energy-state, releasing photons in the process. The methods of transferring energy occur in three separate ways, called "bound-bound", "free-bound", and "free-free" transitions.

Within the plasma, positive ions accelerate toward the cathode while electrons accelerate toward the anode. Neutral atoms move toward the anode at a slower rate, filling some localized pressure differential created by the ions. At normal pressures this motion is in very short distances, because the particles interact and bump into each other, and, exchanging electrons, they reverse direction. Thus, during the pulse neutral atoms are constantly ionizing and recombining, emitting a photon each time, relaying electrons from the cathode to the anode. The greater the number of ion transitions for each electron; the better the conversion efficiency will be, so longer tubes or higher pressures both help increase the efficiency of the lamp. During the pulse, skin effect causes free electrons to gather near the inner wall, creating an electron sheath around the plasma. This makes the area electro-negative and helps to keep it cool. The skin effect also increases inductance by inducing eddy currents in the central plasma.

Bound-bound transitions occur when the ions and neutral atoms collide, transferring an electron from the atom to the ion. This method predominates at low current-densities, and is responsible for producing the spectral-line emission. Free-bound transitions happen when an ion captures a free electron. This method produces the continuum emission, and is more prominent at higher current-densities. Some of the continuum is also produced when an electron accelerates toward an ion, called free-free transitions, producing bremsstrahlung radiation. Bremsstrahlung radiation increases with increasing energy density, and causes a shift toward the blue and ultraviolet end of the spectrum.

Intensity and duration of flash

The only real electrical-limit to how short a pulse can be is the total-system inductance, including that of the capacitor, wires, and lamp itself. Short-pulse flashes require that all inductance be minimized. This is typically done using special capacitors, the shortest wires available, or electrical-leads with a lot of surface area but thin cross-sections. For extremely fast systems, low-inductance axial-leads, such as copper tubing, plastic-core wires, or even hollowed electrodes, may be used to decrease the total-system inductance. Dye lasers need very short pulses and sometimes use axial flashtubes, which have an annular cross section with a large outer diameter, ring-shaped electrodes, and a hollow inner core, allowing both lower inductance and a dye cell to be placed like an axle through the center of the lamp.

In contrast, changes in the input voltage or capacitance have no effect on discharge time, although they do have an effect on current density. As flash duration decreases, the electrical energy becomes concentrated into shorter pulses, so the current density will increase. Compensating for this usually requires lowering the capacitance as pulse duration decreases, and then raising the voltage proportionately in order to maintain a high enough energy-level. However, as pulse duration decreases, so does the "explosion energy" rating of the lamp, so the energy level must also be decreased to avoid destroying the lamp.

The amount of power loading the glass can handle is the major mechanical limit. Even if the amount of energy (joules) that is used remains constant, electrical power (wattage) will increase in inverse proportion to a decrease in discharge time. Therefore, energy must be decreased along with the pulse duration, to keep the pulsed power levels from rising too high. Quartz glass (1 millimeter thick per 1 second discharge) can usually withstand a maximum of 160 watts per square centimeter of internal surface-area. Other glasses have a much lower threshold. Extremely fast systems, with inductance below critical damping (0.8 microhenries), usually require a shunt diode across the capacitor, to prevent current reversal (ringing) from destroying the lamp. If the pulse is allowed to ring through the lamp it will lengthen the flash, so the diode traps the ringing, allowing the lamp to shut down at the correct time.

The limits to long pulse durations are the number of transferred electrons to the anode, sputter caused by ion bombardment at the cathode, and the temperature gradients of the glass. Pulses that are too long can vaporize large amounts of metal from the cathode, while overheating the glass will cause it to crack lengthwise. For continuous operation the cooling is the limit. Discharge durations for common flashtubes range from 0.1 microsecond to tens of milliseconds, and can have repetition rates of hundreds of hertz. Flash duration can be carefully controlled with the use of an inductor.

The flash that emanates from a xenon flashtube may be so intense that it can ignite flammable materials within a short distance of the tube. Carbon nanotubes are particularly susceptible to this spontaneous ignition when exposed to the light from a flashtube. Similar effects may be exploited for use in aesthetic or medical procedures known as intense pulsed light (IPL) treatments. IPL can be used for treatments such as hair removal and destroying lesions or moles.

Lifetime
The lifetime of a flashtube depends on both the energy level used for the lamp in proportion to its explosion energy, and on the pulse duration of the lamp. Failures can be catastrophic, causing the lamp to shatter, or they can be gradual, reducing the performance of the lamp below a usable rating.

Catastrophic failure
Catastrophic failure can occur from two separate mechanisms: energy and heat. When too much energy is used for the pulse duration, structural failure of the glass envelope can occur. Flashtubes produce an electrical arc flash contained in a glass tube. As the arc develops, a supersonic shock-wave forms, traveling radially from the center of the arc and impacting the inner wall of the tube. If the energy level is low enough, a tap against the glass is all that will be heard. However, if the energy level used equals the "explosion energy" rating of the lamp, the impacting shock wave will fracture the glass, rupturing the tube. The resulting explosion creates a loud, sonic shock-wave, and may throw shattered glass several feet. The explosion energy is calculated by multiplying the internal surface-area of the lamp, between the electrodes, with the power-loading capacity of the glass. Power loading is determined by the type and thickness of the glass, and the cooling method that is used. Power loading is measured in watts per centimeter squared. However, because the pulsed-power level increases as the flash duration decreases, the explosion energy must then be decreased in direct proportion to the square root of discharge time.

Failure from heat is usually caused by excessively long pulse-durations, high average-power levels, or inadequate electrode-size. The longer the pulse; the more of its intense heat will be transferred to the glass. When the inner wall of the tube gets too hot while the outer wall is still cold, this temperature gradient can cause the lamp to crack. Similarly, if the electrodes are not of a sufficient diameter to handle the peak currents they may produce too much resistance, rapidly heating up and thermally expanding. If the electrodes heat much faster than the glass, the lamp may crack or even shatter at the ends.

Gradual failure

The closer a flashtube operates to its explosion energy, the greater the risk becomes for catastrophic failure. At 50% of the explosion energy, the lamp may produce several thousand flashes before exploding. At 60% of the explosion energy, the lamp will usually fail in less than a hundred. If the lamp is operated below 30% of the explosion energy the risk of catastrophic failure becomes very low. The methods of failure then become those that reduce the output efficiency and affect the ability to trigger the lamp. The processes affecting these are sputter and ablation of the inner wall.

Sputter occurs when the energy level is very low, below 15% of the explosion energy, or when the pulse duration is very long. Sputter is the vaporization of metal from the cathode, which is redeposited on the walls of the lamp, blocking the light output. Because the cathode is more emissive than the anode, the flashtube is polarized, and connecting the lamp to the power source incorrectly will quickly ruin it. However, even if connected properly, the degree of sputter may vary considerably from lamp to lamp. Therefore, it is impossible to predict the lifetime accurately at low energy-levels.

At higher energy-levels, wall ablation becomes the main process of wear. The electrical arc slowly erodes the inner wall of the tube, forming microscopic cracks that give the glass a frosted appearance. The ablation releases oxygen from the glass, increasing the pressure beyond an operable level. This causes triggering problems, known as "jitter." Above 30%, the ablation may cause enough wear to rupture the lamp. However, at energy levels greater than 15%, the lifetime can be calculated with a fair degree of accuracy.

When operated below 30% of the explosion energy, flashtube lifetime is generally between a few million to tens of millions of flashes.

Applications

As the duration of the flash that is emitted by a xenon flashtube can be accurately controlled, and due to the high intensity of the light, xenon flashtubes are commonly used as photographic strobe lights. Xenon flashtubes are also used in very high-speed or "stop-motion" photography, which was pioneered by Harold Edgerton in the 1930s. Because they can generate bright, attention-getting flashes with a relatively small, continuous input of electrical power, they are also used in aircraft warning lights, emergency vehicle lighting, fire alarm notification appliances (horn strobes), aircraft anticollision beacons, and other similar applications.

In dentistry it is used in "light box" devices to light-activate the hardening of various restorative and auxiliary light-curing resins (for example: Megaflash mini, Uni XS and other devices).

Due to their high intensity and relative brightness at short wavelengths (extending into the ultraviolet) and short pulse widths, flashtubes are also ideally suited as light sources for pumping atoms in a laser to excited states where they can be stimulated to emit coherent, monochromatic light. Proper selection of both the filler gas and current density is crucial, so that the maximum radiated output-energy is concentrated in the bands that are the best absorbed by the lasing medium; e.g. krypton flashtubes are more suitable than xenon flashtubes for pumping YAG lasers, as krypton emission in near infrared is better matched to the absorption spectrum of Nd:YAG.

Xenon flashtubes have been used to produce an intense flash of white light, some of which is absorbed by Nd:glass that produces the laser power for inertial confinement fusion. In total about 1 to 1.5% of the electrical power fed into the flashtubes is turned into useful laser light for this application.

Pulsed light (PL) is a technique to decontaminate surfaces by killing microorganisms using pulses of an intense broad spectrum, rich in UV-C light. UV-C is the portion of the electromagnetic spectrum corresponding to the band between 200 and 280 nm. Pulsed light works with xenon lamps that can produce flashes several times per second. Disinfection robots use pulsed UV light.

A recent application of flashlamps is photonic curing.

History

The flashtube was invented by Harold Edgerton in the 1930s as a means to take sharp photographs of moving objects. Flashtubes were mainly used for strobe lights in scientific studies, but eventually began to take the place of chemical and powder flashbulbs and flash lamps in mainstream photography.

Because electrical arcs could be made that were much faster than mechanical-shutter speeds, early high-speed photographs were taken with an open-air, electrical-arc discharge, called spark photography, helping to remove blur from moving objects. This was typically done with the shutter locked open while in a dark or dimly lit room, to avoid overexposing the film, and a method of timing the flash to the event to be photographed. The earliest known use of spark photography began with Henry Fox Talbot around 1850. In 1886, Ernst Mach used an open-air spark to photograph a speeding bullet, revealing the shockwaves it produced at supersonic speeds. Open-air spark systems were fairly easy to build, but were bulky, very limited in light output, and produced loud noises comparable to that of a gunshot.

In 1927, Harold Edgerton built his first flash unit while at the Massachusetts Institute of Technology. Wanting to photograph the motion of a motor in vivid detail, without blur, Edgerton decided to improve the process of spark photography by using a mercury-arc rectifier, instead of an open-air discharge, to produce the light. He was able to achieve a flash duration of 10 microseconds, and was able to photograph the moving motor as if "frozen in time."

His colleague's interest in the new flash apparatus soon provoked Edgerton to improve upon the design. The mercury lamp's efficiency was limited by the coolest part of the lamp, causing them to perform better when very hot but poorly when cold. Edgerton decided to try a noble gas instead, feeling that it would not be as temperature dependent as mercury, and, in 1930, he employed the General Electric company to construct some lamps using argon instead. The argon tubes were much more efficient, were much smaller, and could be mounted near a reflector, concentrating their output. Slowly, camera designers began to take notice of the new technology and began to accept it. Edgerton received his first major order for the strobes from the Kodak company in 1940. Afterward, he discovered that xenon was the most efficient of the noble gases, producing a spectrum very close to that of daylight, and xenon flashtubes became standard in most large photography sets. It was not until the 1970s that strobe units became portable enough to use in common cameras.

In 1960, after Theodore Maiman invented the ruby laser, a new demand for flashtubes began for use in lasers, and new interest was taken in the study of the lamps.

Safety

Flashtubes operate at high voltages, with currents high enough to be deadly. Under certain conditions, shocks as low as 1 joule have been reported to be lethal. The energy stored in a capacitor can remain surprisingly long after power has been disconnected. A flashtube will usually shut down before the capacitor has fully drained, and it may regain part of its charge through a process called "dielectric absorption". In addition, some types of charging systems can be equally deadly themselves. The trigger voltage can deliver a painful shock, usually not enough to kill, but which can often startle a person into bumping or touching something more dangerous. When a person is charged to high voltages a spark can jump, delivering the high capacitor current without actually touching anything.

Flashtubes operate at high pressures and are known to explode, producing violent shockwaves. The "explosion energy" of a flashtube (the amount of energy that will destroy it in just a few flashes) is well defined, and to avoid catastrophic failure, it is recommended that no more than 30% of the explosion energy be used. Flashtubes should be shielded behind glass or in a reflector cavity. If not, eye and ear protection should be worn.

Flashtubes produce very intense flashes, often faster than the eye can register, and may not appear as bright as they are. Quartz glass will transmit nearly all of the long and short wave UV, including the germicidal wavelengths, and can be a serious hazard to eyes and skin. This ultraviolet radiation can also produce large amounts of ozone, which can be harmful to people, animals, and equipment.

Many compact cameras charge the flash capacitor immediately after power-up, and some even just by inserting the batteries. Merely inserting the battery into the camera can prime the capacitor to become dangerous or at least unpleasant for up to several days. The energy involved is also fairly significant; a 330 microfarad capacitor charged to 300 volts (common ballpark values found in cameras) stores almost 15 joules of energy.

Popular culture
In the 1969 book The Andromeda Strain and the 1971 motion picture, specialized exposure to a xenon flash apparatus was used to burn off the outer epithelial layers of human skin as an antiseptic measure to eliminate all possible bacterial access for persons working in an extreme, ultraclean environment. (The book used the term 'ultraflash'; the movie identified the apparatus as a 'xenon flash'.)

Animation

Frame 1: The tube is dark.

Frame 2: The trigger pulse ionizes the gas, glowing with a faint, blue light. Spark streamers form from each electrode, moving toward each other along the inner surface of the glass tube.

Frame 3: Spark streamers connect and move away from the glass, and a plasma tunnel forms allowing current to surge.

Frame 4: Capacitor current begins to run away, heating the surrounding xenon.

Frame 5: As resistance decreases voltage drops and current fills the tube, heating the xenon to a plasma state.

Frame 6: Fully heated, resistance and voltage stabilize into an arc and the full current load rushes through the tube, causing the xenon to emit a burst of light.

title: Flashtube


text:
Talk:Gutzon Borglum

Fathers bigamy
Gutzon Borglum's father had two wives, not more. The fact is, he was a bigamist not a polygamist. Wetman 17:27, 4 Dec 2003 (UTC)

 * Agreed. However, the practice (if he was indeed LDS) would have been called Plural Marriage or Polygamy from his viewpoint. That is why the change was made. I'll change to plural marriage with an explanation. Thanks. Visorstuff 23:16, 4 Dec 2003 (UTC)
 * That's fine now. Wetman 10:48, 5 Dec 2003 (UTC)

Rushmore timeline
How Long did it take him? (Anon.)
 * He was still hard at work at mt Rushmore when he died. his son quickly wrapped up the project, pretty much complete as it was. --Wetman 21:50, 26 Jan 2005 (UTC)

Image
I uploaded Image:Gutzonborglum.jpg from the Library of Congress to replace the first image of the article, which has an obselete PD tag. Problem is, I forgot to remove the frame of the image (and I don't have Paint Shop Pro or other Graphics software). Can somebody quickly remove the frame and re-upload it? Thanks, AndyZ 00:20, 22 March 2006 (UTC)

KKK 'sympathetic connections' or 'membership'?
The article says: "At Stone Mountain he developed sympathetic connections with the reorganized Ku Klux Klan, who were major financial backers for the monument." But according to Stone Mountain, he was a Ku Klux Klan member, which is more than just having sympathetic connections. The two articles should be resoved. --Mmathu 07:06, 16 June 2006 (UTC)

It says he's a member in the Mount Rushmore article, as well. Glitterglue 23:29, 13 October 2006 (UTC)
 * According to the Shaff's book on Borglum, Six Wars at a Time, which includes about 20 references to the KKK in the index, he was a member. As with most things surrounding this complex man it is not a simple as it might seem wher we talking about joining the KKK in 2006.  The KKK was being reinvented starting in 1915, the time at which Borglum was spending a lot of time in Atlanta trying to get funding for his Stone Mountain project.  He saw the newly emerging KKK as being a source for such finincial resources. He also saw the KKK as being a rural populist movement, set up to hopefully wrest power from the urban capitalists who were running the country.  Long story short, Gutzon Borglum was a member of the KKK.  Carptrash 14:11, 14 October 2006 (UTC)

 * I suggest that the 'sympathetic connections' comment in this article be changed accordingly. Any disagreement? — Mmathu 07:10, 17 October 2006 (UTC)
 * Here is what 6 Wars says.
 * By joining and trying to mold the Klan, Gutzon was not seeking personal power. He did not want to wear a hood and robe, stand before a burning cross or preach a morality based on fear or floggings. Gutzon was a Klansman, but not for the reasons  held by most other Klansmen.  p. 197
 * So my guess is that a lot of foks will view his being a member in terms of the Klan today, but oh well. Carptrash 15:34, 17 October 2006 (UTC) PS I wish you'd register as a wikipedian, Mmathu.

While there isn’t proof that Borglum officially joined the Klan, which helped fund the project, “he nonetheless became deeply involved in Klan politics,” John Taliaferro writes in Great White Fathers.

John Taliaferro is a graduate of Harvard College and a former senior editor at Newsweek Darkhumor67 (talk) 22:12, 3 July 2020 (UTC)

I just moved this to discussion
"(anscestor of elizabeth jean troyer who currently resides in boise idaho. her father was his favorite nephew) "
 * If it is to stay in the article - - -- well we need to discuss it. Carptrash 14:20, 5 December 2006 (UTC)

Poop on him?
One S.O.B has written the following:

(John) Gutzon de la Mothe Borglum (March 25, 1867 – March 6, 1941) was the American sculptor famous for creating the monumental presidents' heads at Mount Rushmore, South Dakota, as well as dozens of other impressive public works of art. POOP ON HIM

I somehow couldn't find it in the "edit this page". Can someone look into it?
 * You were looking at an older, already fixed version of the article. Or perhaps it was getting fixed as you saw it. Borglum gets a fair amount of these sorts of edits, which is the price we pay for allowing Jr. high school kids to edit.  Who was it that said said that " eternal vigilance is the price of freedom"? Anyway, this is why many/most dedicated wikipedians do vandalism patrol. Carptrash 14:45, 6 December 2006 (UTC)

I just cut this sentence out
and we can talk about it here (I added the bold).
 * and the Stone Mountain carving in Stone Mountain, Georgia, which is the largest Confederate monument

The Stone Mountain fiasco is discussed in the article, but since none of Gorglum's work there remains, the sentence (opinion) does not really belong in the introduction. Carptrash 06:48, 3 February 2007 (UTC)

Harvard Technical College
What is Harvard Technical College? I've never heard of it. I can't find search results outside of this article. Schear (talk) 17:12, 22 November 2008 (UTC)

Mount Rushmore
What is the source for the statement that the entire Louisiana Purchase was sacred Native American territory? There were a lot of tribes in the Mississippi/Missouri River drainage, and the sentence implies that all of them thought that the whole area was sacred.

And, more specifically, what is the source for the statement the Borglum's reason for including Jefferson was that the Indians thought that the area of the Louisiana Purchase was sacred? Broadcaster101 (talk) 06:15, 1 April 2010 (UTC)
 * I think what is intended here is a two part thing. One, Jefferson was added to the group because he added the Louisiana Purchase to the United States  (I have a source for that ) and secondly, that the Black Hills were sacred land to some native peoples.  This whole section can probably be improved. Einar aka Carptrash (talk) 15:08, 1 April 2010 (UTC)

I just moved an entire section here to talk about
Here it is:
 * == Controversy ==
 * '' "Controversy surrounding the alleged racist roots of the building of Mt. Rushmore is well documented. Many claim it was not an innocent gesture to commemorate George Washington, Thomas Jefferson, Theodore Roosevelt, and Abraham Lincoln, rather, a warning, if not blatant threat, to any race besides white, that whites ruled the United States of America and not Blacks, Mexicans, or especially Indians.

 * ''Many claim that Gutzon Borglum, the creator, was not accepting of other races and that his contribution to the dominant ideology of the era not only exalts the contribution of whites to the making of America civilization, but tries to exclude blacks from the myth of America’s new creation. Borglum’s view of America was that of a white nation in conflict with other racial and ethnic groups, some of whom came before the Europeans, such as Hispanics and Native Americans, and others, such as Africans and Asians, who were used as laborers to build the countries material infrastructure.

 * While at Stone Mountain, it is said that Borglum became a senior advisor to the newly reborn Ku Klux Klan. Whether this accorded with a racist world view, or if it was simply one way to bond with some of his patrons on the Stone Mountain project, is unclear. Borglum's motivations for dealing with the KKK may be hazy, but the association has long been a matter of public record. "

I don't believe that statements such as ",,,,is well documented" can be allowed to stand without the documentation being revealed. the same is true for the statement "Many claim that ... " without at least some suggestion as to who the "many" might be. Ditto for " long been a matter of public record." Please tells us where in the record. It should not be too hard. An article on Borglum without a Controversy section is like an egg with out salt, or as my grandmother once said, "a kiss without a beard." However it needs to be done right and I believe that what we have here ain't right. Einar aka Carptrash (talk) 23:37, 29 October 2011 (UTC)

Construction of Rushmore
It took 1 million years for this to form naturally. — Preceding unsigned comment added by 162.220.110.66 (talk) 13:37, 5 January 2017 (UTC)

External links modified
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Borglum and the KKK
First of all, I have been editing on this article for about 15 years or so and not just dragged in recently. Borglum has over 200 works listed on SIRIS, one is tied to the Klan - probably a few others to the United Daughters of the Confederacy. This KKK connection needs to be, and is, discussed in the article. It does not belong in the lede. It is not an important component of his life and career. I see it has been bounced around a bit, they way we deal with that sort of thing is on the talk page. This is big news today for several reasons but wikipedia is not a newspaper. I plan on removing the KKK from the lede, but you have a chance to discuss it first. Carptrash (talk) 05:41, 5 July 2020 (UTC)
 * I think that, given his work, we should include something about his motivations. His work was solely lionising heroes of the White colonial state, he was by all accounts waist-deep with the KKK, the Daughters of the Confederacy, and personally deeply racist. Yes, this moment is racially charged, and that's perhaps a moment to consider why we would consider including something in the lede mentioning his motivations for making this art. Even the Rushmore museum has letters from convicted a KKK racially-motived rape-murderer to him in it to highlight his complicity and motivation for sculpting it! My counterpoint is the lede to date has been lacking and his racism, which literally scars the landscape in multiple places, shouldn't be dismissed. He was part of a large campaign that successfully stripped the rights of African Americans and those organisations remain in operation today. (The offices of the DoC were burnt just two weeks ago by protesters, and they continue to put up lionising art of the Confederacy to this day - they just did so in Newport RI.) Ogress 06:37, 5 July 2020 (UTC)
 * Can we just stop putting the reference in the lede until we hash this out? I agree with Carptrash that it was not a major factor in his life and should not be included in the lede, but that's my opinion.  Also, for the love of god whomever keeps deleting ANY reference to the KKK needs to stop.  It's a documented fact and keeping it out of the article all together is just wrong. zimmhead (talk) 14:55, 5 July 2020 (UTC)
 * I just chopped this section out of the lede because it was just cut & pasted from the source. In any case it does not belong in the lede.
 * "His sculptural work was associated with his belief in white supremacy. The son of polygamist Mormons from Idaho, Borglum had no ties to the Confederacy, but he had white supremacist leanings. In letters he fretted about a 'mongrel horde' overrunning the 'Nordic' purity of the West". " Carptrash (talk) 18:18, 5 July 2020 (UTC)
 * I feel as if I should respond to your issue laden post. Your statement “His work was solely lionizing heroes of the White colonial state” reveals a misunderstanding of much of his work.  Yes, it was (is?) true, as sculptor Janet Scudder once wrote, “ I won’t add to this obsession of male egotism that is ruining every city in the United States with rows of hideous statues of men-men-men-each one uglier than the other-standing, sitting, riding horseback-every one of them  pompously convinced that he is decorating the landscape.” that white guys in suits and uniforms were the most popular subjects of the day.  And likely many of these men were the heroes of the white colonial state.  Especially if one uses the most widespread definition of the word “colonial.”  Was Lincoln a hero of the colonial state?  Borglum’s bust is found at Lincoln’s tomb in Springfield, IL, and his other Lincoln’s are in probably dozens of museums, parks and the like across America.  But of course if Lincoln is just another “colonial” that just proves your point.  He did memorials to Gov. John Peter Altgeld, who ruined his political career by pardoning some of the Haymarket Affair convicted, he did a piece for Sacco and Vanzetti, who no one would call representatives of the “White colonial state.”  He did several about the early white settlers in Newark NJ & Ohio, but is that just more “White colonial state” stuff?  “Simon Bolivar?”  He did some architectural angels at St. John the Divine in NYC and gargoyles at Princeton.  In any case, there is enough here to suggest that his work was not “solely” . …what you said. His motivations for making his art was almost always 1) money and 2) fame or attention.  His “letters from convicted a KKK racially-motived rape-murderer” - that would be D. C. Stephenson, would predate the rape murder (I can find nothing “racially motivated” about this horrifying attack on a white woman”), so Borglum is not related to that sordid stuff at all.  That you are bringing up stuff happening now, in Newport and elsewhere, seems to suggest that you are working on a bigger picture than just the life and work of Borglum.  He was a racist.  That need s to be in the article, but not in the lede. Carptrash (talk) 20:06, 5 July 2020 (UTC)
 * An artist's work and not their political beliefs are what should be important in art biography pages. A sculptor such as Borglum is notable for his art, not who he was associated with in his time away from the chisel. If the work of art is directly related to an artist's beliefs and issues, such as Picasso and Guernica, then that could be mentioned on the artworks lead. Since Borglum sculpted a few Southern-oriented pieces, maybe those articles are where his affiliations might be important, but adding them to his short biography lead, let alone the first sentence, seems undue and purposely weighted towards a controversy which is unrelated to his body of unaffiliated artwork. Randy Kryn (talk) 23:30, 5 July 2020 (UTC)
 * I agree that having the information in the lede, especially in the first sentence, is undue emphasis. It does belong somewhere in the article. Carlstak (talk) 11:18, 6 July 2020 (UTC)
 * And I dont agree.
 * First - Leni Reifenstahl... "was a German film director and actress and Nazi sympathizer." → In the lede. First sentence!
 * Second - David Wark Griffith ... "was an American film director. Widely considered as the most important filmmaker of his generation, he pioneered financing of the feature-length movie. His film The Birth of a Nation (1915) made investors a profit, but also attracted much controversy, as it depicted African Americans in a negative light and glorified the Ku Klux Klan."→ In in the lede! --93.211.217.142 (talk) 00:13, 12 July 2020 (UTC)

 * Above is the claim, "solely lionising heroes of the White colonial state." What is your proof that he only sculpted colonial figures? Jonathan Edwards? William Bradford? Myles Standish? Capt Smith & Pocahontas? Two are colonial figures: George Washington and Thomas Jefferson; not ONLY colonial: Abe Lincoln & Teddy Roosevelt are not colonial. (PeacePeace (talk) 04:36, 12 July 2020 (UTC))

Whether or not Borglum was a member of the KKK is disputed. Smithsonian says no proof of officially joining.
Since this is a hot issue, I think we need to have solid proof for membership in KKK before asserting it. The secondary source which claims it must be examined to see if it cites at least 2 reliable primary sources. Thus I have deleted the definitive claim in the article. Such a claim requires at least 2 reliable secondary sources, both of which document primary sources. The article records the denial by Borglum, which requires strong evidence to brush it off. A mere opinion that "it was for public consumption" is insufficient. (PeacePeace (talk) 04:27, 12 July 2020 (UTC)).
 * A 2023 book states: An ardent white supremacist, Borglum was closely associated with the Ku Klux Klan. There is no documentary proof that he actually joined it, but his various prejudices became more pronounced after 1923 when he became directly involved with the group. (bold mine) Schazjmd   (talk)  23:11, 22 July 2023 (UTC)

Relationship with D. C. Stephenson
The section Public Life concludes by saying, 'The museum at Mount Rushmore displays a letter to Borglum from D.C. Stephenson, the infamous Klan Grand Dragon who later was convicted of the rape and murder of Madge Oberholtzer. The 8x10 foot portrait contains the inscription "To my good friend Gutzon Borglum, with the greatest respect."' Grammatically, the letter and the portrait appear to be the same artifact. Will someone who knows the facts please unscramble this? J S Ayer (talk) 03:53, 29 August 2020 (UTC)

Politics ? ? ?
Other than a one liner about the Bull Moose Party and KKK speculation, there's nothing about his politics.

I'd like to know whether or not he 'belonged' to any other political party after the Bull Moose collapsed in 1920. 2600:8800:204:C400:7088:1EE1:13F1:F556 (talk) 21:22, 27 January 2023 (UTC)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Talk:Gutzon Borglum


text:
DJ Hell

Helmut Josef Geier (born 6 September 1962), known professionally as DJ Hell, is a German DJ.

1970s and 1980s
DJ Hell described his musical beginnings in an interview with The European, telling them “I was socialized with German electronic music of the 1960s and 1970s. There were no commercial aspirations; it was all about experimentation.”

Hell has worked as a DJ since 1978. Starting in 1983, he began working as a DJ at Club Libella in Kirchweidach, Germany, near his hometown of Altenmarkt an der Alz. This would be his first residency, where he cultivated his eclectic style of mixing New Wave, Ska, Punk, Rockabilly, Hip hop, and Disco in the same set. Further residencies followed, at Park Café and Tanzlokal Grössenwahn in Munich, where, as one of the first house DJs in Germany he regularly performed at house music parties. In 1987 he organized the first acid house party there, and in the same year at Grössenwahn deejayed at Run–D.M.C.’s aftershow party. At the end of the 1980s, he developed his style at various Munich clubs and dance halls from New Wave, EBM, Electro, and Hip hop to include House and Techno.

1990s
In the early 1990s, DJ Hell was resident DJ at Germany's first afterhours club Babalu Club in Munich. In 1991, Hell was instrumental in establishing Peter Wacha's label Disko B, and until 1996 was closely involved as A&R. The label's first release in 1991, Silicon Soul’s track Who Needs Sleep Tonight was licensed by Hell, who produced a remix for the b-side: The DJ G. Hell Remix. To sign the contract with the New York band, he flew to New York City. Disko B Records was launched for the release.

Hell's first self-produced single, My Definition of House Music (on R&S) became a club hit in 1992 with over 100,000 records sold, drawing recognition to DJ Hell among the first generation of Techno DJs who also released records.

During his time with Disko B and until 1997, DJ Hell was also a resident DJ at Ultraschall, Munich's first pure techno club, located on the site of the former Munich-Riem Airport and later at the former Pfanni factory compound Kunstpark Ost. During the 1990s DJ Hell had further residencies in Berlin, at E-Werk and WMF, from 1992 at Tresor, and in the 2000s at Watergate.

Parallel to his A&R work in Munich, in 1992 DJ Hell became A&R manager for the label Logic Records in Frankfurt, and in the same year compiled the world's first trance compilation, Logic Trance.

In 1993 he lived for a year in New York City, where was booked as a resident DJ at Limelight, together with Jeff Mills. In 1994 DJ Hell moved to Berlin and worked for the record store Hard Wax. Hell's debut album Geteert & Gefedert (Tarred & Feathered) was released on Disko B in 1994. In 1995, he moved back to Bavaria.

That same year, Hell was the only German DJ to be invited to be on a John Peel Session, including a radio interview, in London. The session was released that year on Disko B.

In addition to his work as a DJ and producer, in 1996 he founded the label International Deejay Gigolos in Munich, for which he served from the first day onward as the label mastermind, A&R, and art director. Parallel to managing the label, as a DJ and event organizer, Hell also curated over 40 Bavarian Gigolo Nights featuring international DJs and live bands in various clubs in Munich.

During this period in the late 1990s, numerous releases on International Deejay Gigolos notably fuelled the 1980s revival in the German and international club scene, establishing DJ Hell as one of the founders of the Electroclash subgenre. International Deejay Gigolos has released works by big names on the international Techno, House, and Electro scenes, including Jeff Mills, Miss Kittin & The Hacker, Dave Clarke, Tiga, Fischerspooner, Dopplereffekt, Vitalic, Bobby Konders, The KLF, Tuxedomoon, and Laurent Garnier. Fischerspooner was discovered by DJ Hell and debuted on International Deejay Gigolos. Stylistically, International Deejay Gigolos focused, beyond the Electroclash genre, also on Electro, EBM, electronic avant-garde House, Tech-House, and Techno, with influences from 1980s Pop and Disco. In the 20 years spanning 1996 to 2016 that he has handled A&R for the label, Hell has released over 300 singles and albums on International Deejay Gigolos.

In 1998, Hell's second album Munich Machine was released on Disko B and V2 Records. According to The Guardian Munich Machine was an important record that helped to catalyse electroclash. According to the music magazine De:Bug: “Munich Machine feels like the result of a dynamic collaboration by Munich residents engaged in the club scene and who know how to work with it. Every aspect of it has been carefully crafted and sometimes it seems as if DJ Hell is using this kind of mega-mix to grow beyond himself. This is particularly evident when he mixes together very different sources.”

In 1999, Arnold Schwarzenegger sued International Deejay Gigolos for using his picture in the logo. Hell had to stop selling all records that bore the logo and pay a fine of 150,000 euros.

2000s
From 2000 to 2003, he ran the disco and nightclub Villa Traunstein, located in the Bavarian town of Traunstein, where he was responsible for the club's high-profile, international DJ bookings, including the likes of WestBam, Sven Väth, and Jeff Mills.

In 2003, DJ Hell lived for a second time in New York City, where he produced his third studio album NY Muscle, for which he collaborated with several artists, including Alan Vega, Erlend Øye, James Murphy, and singer Billie Ray Martin. The website allmusic.com wrote about NY Muscle: “This is the sound of nighttime New York City from the outsider perspective of an infamous German named Hell, and it’s dark, dark, debauched fun.”

Since 2005, DJ Hell has been based in both Munich and Berlin, and moved the label office to Berlin. Since the early 2010s Hell lives again mainly in Munich and in his hometown Altenmarkt at the Chiemsee.

From 2007 to 2010, he served as musical coordinator for Berlin fashion designer Michael Michalsky, for whose fashion shows he regularly produced the music. Hell has also performed at the after-show parties of Michael Michalsky's StyleNite, held during the Berlin Fashion Week. DJ Hell has been producing music for fashion shows since the mid-1990s, for the likes of Hugo Boss, Raf Simons, Patrick Mohr, Dirk Schönberger, and Donatella Versace – ever since he was first asked by fashion designer Kostas Murkudis to accompany one of his fashion shows in Berlin with music.

DJ Hell occasionally works with renowned fashion labels, either lending his name or collaborating as a designer. This work has given rise to an underwear collection for Wendy & Jim, women's underpants for Agent Provocateur, CD cases for Magma, and a pair of glasses for Freudenhaus. In 2004, Karl Lagerfeld photographed DJ Hell for V Magazine. These photographs were then exhibited at a gallery in Berlin. DJ Hell on his affinity for fashion (in SPEX #316/2008, p. 95f): “In England, fashion and music have gone together for decades. In Germany, however, one tends to deny a musician’s competence if he defines himself superficially, that is, according to things that are visible. Just think of David Bowie on the male side, and Grace Jones on the female side, and it becomes clear that a union between fashion and music can be incredibly prolific.”

As a DJ, Hell has toured worldwide, and repeatedly headlined international festivals such as the Loveparade and Mayday in Berlin, Fuji Rock and Wire in Tokyo, the Montreux Jazz Festival, and the Time Warp Festival in Mannheim. He was the first Techno DJ to perform at the University of Havana in 1997. The performance was filmed by a German film crew directed by Torsten Schulz, and screened in 2000. In 2002, Romuald Karmakar shot a segment of his film “196 BPM” during a performance by Hell at WMF.

In 2003, GQ magazine named DJ Hell “Man of the Year” in the category of music.

In 2009 Hell released the album Teufelswerk (Devil’s Work), which again features several international guest stars, such as Bryan Ferry, Peter Kruder, P. Diddy, Roberto di Gioia, Mijk van Dijk, Christian Prommer, and Billie Ray Martin. The double album is conceptually divided into “day” and “night” parts, and ranked in the Top 50 of the German Media Control charts.

According to Hell in an interview with Resident Advisor: “I did Kosmische Musik in a new way. This is where I come from, I grew up with the early German electronic pioneers of music, and this is why I went in this direction. Often it is called German electronic avant-garde, or psychedelic music. I went back to the '70s and tried to do it in my own way.”

The Guardian on Teufelswerk: “With Hell acting as conductor, and Kruder, Prommer, and Roberto di Gioia playing a mixture of synths, acoustic guitars, Wurlitzers and ‘rhythm machines,’ the four sweep back and forth across Europe, mapping the psychic highways that link Kraftwerk's Düsseldorf and Jean Michel Jarre's imaginary, futuristic Paris; Pink Floyd at the UFO Club in 1966, and Café del Mar in 1987; cavernous booming dubstep nights in modern Berlin and Goblin's progressive 1970's Italy.”

Since 2009, DJ Hell has supported the feminist Ukrainian activist group FEMEN with various DJ and television appearances.

The self-confessed fan of the FC Bayern Munich soccer club is a jersey sponsor for TSV Altenmarkt, the football club of his hometown. Contrary to rumors, he does not possess a professional coaching license. For the 2006 FIFA World Cup, Hell was booked as a DJ for the opening ceremony at the Olympic Stadium in Berlin, but the event was canceled on short notice by FIFA.

DJ Hell on his football passion in Alert, 8/2002: “I watch the home games of FC Bayern Munich. I also represented Germany as a DJ at the recent European and World Championships, travelling with the German national team from city to city, and deejayed on the evening before the games. My contract stated that the organizer had to get me tickets for the games.” (See Alert 8/2002, p. 51)

2010s
In 2013, DJ Hell's remix of Tim Deluxe's track Transformation held the number 1 position on the Beatport techno charts for nine weeks.

In the same year, DJ Hell performed an hour live on Boiler Room TV on the occasion of the 1st birthday. This clip soon became a viral hit, with almost 880,000 views (Status: December 2020).

The countertenor and new wave singer Klaus Nomi interpreted Henry Purcell's original composition from the opera “King Arthur” spectacularly in 1982 as an early hybrid of electronic and classical music. DJ Hell, who has admired Klaus Nomi since his early days as a DJ and has always DJ'd him, bought the rights to the original composition and released his reworked version of the song as a single on International Deejay Gigolos in 2014.

In 2015, DJ Hell gave a lecture together with Sascha Arnold at the Munich Chamber of Architects with a picture presentation about club architecture and culture in Munich during the 1970s and 1980s. In the same year, Electronic Beats by Telekom filmed a Slices documentary about DJ Hell.

For the Design Hotel Flushing Meadows in Munich, DJ Hell designed one of eleven hotel rooms on the third floor in 2015. The room is designed entirely in black color and houses as a design element a life-size band of metal skeletons on keyboard, electric guitar and mic stand above the bed.

For the 2015/16 winter collection of fashion designer Boris Bidjan Saberi, who now lives and works in Barcelona, DJ Hell produced the music in 2015, which can also be heard in an official promotional video by Saberi.

In spring 2017, DJ Hell's fifth album Zukunftsmusik was released. Like his studio album Teufelswerk released eight years earlier, it was co-produced by Peter Kruder in Vienna. On Christmas Eve 2016 appeared with I Want U  the first single release from the album. The accompanying video, produced by Hell, features animated gay comic artwork by Finnish artist Tom of Finland, who was known for homoerotic drawings of masculine men. The press photos for the album were taken by photographer Greg Gorman at his home in Los Angeles. Sven Marquardt, the photographer and bouncer of the techno club Berghain, was also involved with various photographs on DJ Hell covers of International Deejay Gigolos.

DJ Hell about future music: “This album is largely to be understood as a homage to gay culture, which with disco, house, Frankie Goes to Hollywood and techno can be seen as the nucleus of club culture. Club culture as we know it today is based at its core on the gay house culture invented by dj Ron hardy at Chicago's Warehouse and paralleled by Larry levan at New York's Paradise Garage.”

In Gerrit Starczewski's 2017 Ruhrpott road movie Pottorginale, DJ Hell embodied a hitman. The sequel to the film, in which DJ Hell plays the pop singer Helmut, is scheduled for March 2021.

At the International Short Film Festival Oberhausen of 2017, DJ Hell's video I Want U took second place of the "MuVi Award". The jury judged the 4-minute video: “A beautiful collaboration that elevates both DJ Hell's music and Tom of Finland's imagery to a common and higher level. Funny, sexy and intelligent in its use of graphic material, I Want U builds on a concept that is confidently sustained. The film is simple but not repetitive, using variations in the music to drive the imagery. Full of allusions to the history of the music video, this is an original look at a much-loved part of the subversive canon.”.

For Balenciaga Paris, DJ Hell produced a DJ mix for various 3D art videos: Balenciaga Loop 05 - Nightlife and Balenciaga Loop 06 - After Hours He also played at the 2017 & 2018 aftershow parties.

The own perfume – Helmut Josef Geier – was released in 2018, under the name DJ Hell “Techno”. It was presented at the Berlin Soho House store. "My first perfume is based mainly on incense components. It gets its freshness from citrus elements and earthy components. I can't reveal all the ingredients, but churches, like clubs, have always been meeting places for believers. I understand club music and club culture as faith, so a religion of its own.".

DJ Hell composed the soundtrack for the film Yung, which actor and director Henning Gronkowski shot in 2019. "The film," said DJ Hell in an interview with the Frankfurter Rundschau, "portrays daily lives of girls in the Berlin party jungle, unvarnished, direct and sensitive." The soundtrack wa released on Hell's new output The DJ Hell Experience. The film had its world premiere at the Münchner Filmtage 2019.

In the late-night show Ringlstetter (BR), DJ Hell was a guest of Hannes Ringlstetter in September 2018.

Since 2020
In 2020 DJ Hell founded a new label called The DJ Hell Experience. The Hamburg-based distributor wordandsound is responsible for distribution. For the first album released under the new label, House Music Box, the artist Jonathan Meese contributed a picture for the cover. The electronic music magazine FAZEMAG chose House Music Box as the Album of the Year 2020. The album's first video features a Hell avatar, which will also be used at festivals and shows in the future. Another collaboration with Meese is the album Meese x Hell - Hab keine Angst, hab keine Angst, ich bin deine Angst, to be released in April 2021 by Daniel Richter’s Buback, records Hamburg.

In March 2021, Soft Cell - Tainted Love Remix 2021 was released on Cleopatra Records in the U.S.

To the book ''Mensch – Maschinen – Musik. Das Gesamtkunstwerk Kraftwerk,'' edited by Uwe Schütte (publication date February 2021), DJ Hell has written a detailed personal foreword.

In the exhibition “Nachts. Clubkultur in München“ („Nights. Club Culture in Munich”), which the Munich Stadtmuseum will be showing from April 2021 to January 2022, DJ Hell will play a significant role – he plans to make his record collection available to the museum for the show. The cultural-historical exhibition is dedicated to Munich's nightlife and club culture from the post-war period to the present in the form of a nocturnal foray.

DJ Hell is one of the DFB ambassadors for the 2024 European Football Championship to be held in Germany, the UEFA Euro 2024.

DJ Hell is the designated curator of the nascent Museum of Modern Electronic Music (MOMEM) in Frankfurt am Main.

Awards

 * “Most successful national A&R,” Dance Music Award, 2001
 * “Man of the Year,” GQ Magazine, 2003, category: music
 * “Best DJ,” Music and Machine Award, Berlin, 2004
 * “Best Techno DJ” (nominee), DJ Awards, 2007
 * “Best Techno DJ” (nominee), DJ Awards 2008
 * “Best German Act,” Echo nominee, Berlin, 2009
 * “Best German Album”, Echo nominee, Berlin, 2009

Groove Magazine Reader Polls

 * 1995: DJ National: 2nd place
 * 1996: DJ National: 2nd place
 * 1997: DJ National: 2nd place
 * 1997: Label National: 1st place
 * 1998: DJ National: 2nd place
 * 1998: Label National: 2nd place
 * 1999: National: 2nd place
 * 1999: Label National: 3rd place
 * 2000: DJ National: 3rd place
 * 2000: Label National: 3rd place
 * 2001: National: 2nd place
 * 2001: Label National: 1st place
 * 2002: National: 2nd place
 * 2002: Label National: 2nd place
 * 2003: National: 3rd place
 * 2003: Label National: 4th place
 * 2004: National: 3rd place
 * 2004: Label National: 3rd place

Spex Magazine Reader and Editors’ polls

 * SPEX 1/99: Year in Review 1998 // Editors’ Picks for Best Album: 43rd place: DJ Hell: Munich Machine
 * SPEX 1-2/01: Year in Review 2000: Reader Polls for Best DJ: 2nd place: DJ Hell
 * SPEX 1-2/02: Year in Review 2001: Reader Polls for Best DJ: 2nd place: DJ Hell
 * SPEX 1-2/03: Year in Review 2002: Reader Polls for Best DJ: 2nd place: DJ Hell
 * SPEX1-2/04: Year in Review 2003: Reader Polls for Best Song: 26th place: Hell Feat. Erlend Øye: Keep on Waiting
 * SPEX1-2/04: Year in Review 2003: Reader Polls for Best album: 36th place: Hell: NY Muscle
 * SPEX1-2/04: Year in Review 2003: Reader Polls for Best DJ: 2nd place: Hell
 * SPEX 1-2/05: Year in Review 2004: Reader Polls for Best DJ: 2nd place: DJ Hell
 * SPEX 1-2/06: Year in Review 2005: Reader Polls for Best DJ: 2nd place: DJ Hell
 * SPEX 1-2/07: Year in Review 2006: Reader Polls for Best DJ: 2nd place: DJ Hell
 * SPEX 1-2/10: Year in Review 2009: Editors’ Picks for Best Album: 35th place: Hell: Teufelswerk
 * SPEX 1-2/10: Year in Review 2009: Reader Polls for Best Album: 37th place: Hell: Teufelswerk
 * SPEX 1-2/10: Reader Polls Best Song: 26th place: Hell: Electronic Germany

Discography

 * Geteert & Gefedert (Disko B)
 * Mixes Of Gary Numan Vol. 2 (Random Records)
 * Repassion (International Deejay Gigolo Records)
 * My Definition Of House Music (R&S)
 * Red Bull From Hell EP (Disko B)
 * Sprung Aus Den Wolken / Butter Säure (Kickin Records)
 * Three Degrees Kelvin / Like That! (Magnetic North)
 * Ultraworld EP Vol. 1 (Disko B)
 * Allerseelen (Disko B)
 * Albino EP (Disko B)
 * Original Street Techno (Disko B)
 * Totmacher (Disko B)
 * Totmacher Interpretationen (Disko B)
 * Munich Machine (V2 Records, Inc.)
 * Suicide Commando (V2 Records, Inc.)
 * Copa (Disko B)
 * Rock My Body To The Beat (International Deejay Gigolo Records)
 * Keep On Waiting (International Deejay Gigolo Records)
 * N.Y. Muscle (2003, Motor Music)
 * Listen To The Hiss feat. Alan Vega (International Deejay Gigolo Records)
 * Je regrette Everything feat. Billy Ray Martin International Deejay Gigolo Records)
 * Best of Hell (International Deejay Gigolo Records)
 * Fun Boy (International Deejay Gigolo Records)
 * Teufelswerk (2009, International Deejay Gigolo Records)
 * Teufelswerk House Remixes Part I (2011, Embassy of Music)
 * Teufelswerk House Remixes Part II (2012, Embassy of Music)

For a complete discography see the article about DJ Hell in the German Wikipedia.

Films

 * Durch die Nacht mit … mit Bai Ling and DJ Hell (Documentary, directed by Hasko Baumann, ARTE, 2005)
 * Fürst Nachtleben – DJ Hell (Documentary, written and Directed by Hilde Bechert, Bayerischer Rundfunk, 2006.)
 * Freak Show (Directed by Angelika Leppert, Producer: DJ Hell, International DJ Gigolo Records, 2005.)
 * 196 bpm – Die Nacht der Raver (Documentary, directed by Romuald Karmakar, Pantera Film, 2002.)
 * Techno Salsa (Documentary, directed by Torsten Schulz, Absolut Medien, 1999.)

title: DJ Hell


text:
User:Millosh

 * email: millosh@gmail.com
 * Jabber: millosh@jabber.org
 * Jabber: millosh@gmail.com
 * #wikimedia@freenode: millosh

Permissions
For now, I got one permission for using material from other sites here:

 * Permissions from Robert Elsie for the material related to Albanian culture (email source).

Other

 * My workshop
 * TODO

sr:Корисник:Милош

title: User:Millosh


text:
User:DrinkBoy

I've "joined" up to Wikipedia to hopefully infuse some more accurate information into the "Cocktail" section of this site :->

For more information about me, the site I run, refer to:

http://www.drinkboy.com/press/

-Robert Hess www.DrinkBoy.com

title: User:DrinkBoy


text:
Dorney

Dorney is a village and civil parish in Buckinghamshire, England. It borders the River Thames to the west and south, and is bisected by the Jubilee River. In 2011 it had a population of 752. It is 2.3 mi west of neighbouring Eton, which is a slightly larger parish.

It includes a grade I listed manor house, Dorney Court, as well as the largest rowing lake in the south of England, Dorney Lake. Altogether water accounts for 13% of Dorney, the highest proportion in Buckinghamshire.

History
Dorney Manor was mentioned in the Domesday Book, and was famed for honey; it is named after the Saxon for "Island of Bees".

Dorney Court
Dorney Court adjoins the centre of the village and has comparable grounds to other village centre properties. It was, however, the manor house, so owned much of the land of the village until the late 18th century. It dates to the early Tudor period and is made from a timber frame with red brick. Its roof has original tiles. It has bold star-shaped timbers and a large fireplace with panels from Faversham Abbey, Kent.

One account of its early history reveals that the then adjoining Boveney manor, at the southern end of the village of Burnham, had an oak tree cut down by an employee. He defended his conduct by declaring that at a court in Buckinghamshire previously found Dorney to be a royal manor and that the green was therefore common land, so it was legal to cut the tree down.

A notable owner was William Garrard, who bought Dorney Court in 1542; he was later Lord Mayor of London from 1555 to 1556). Major C. H. D. Palmer owned it in 1925, having been passed down by earlier Palmers since 1624. Until after 1925, the manor's family owned the rectory and maintained the church, a state of affairs which ended with the ending of all tithes in England and Wales.

Other history
The first pineapple in the UK was grown in Dorney Court, leading to a pub in the village being named The Pineapple. It is Grade II listed for its age, dating half to the 17th century and half to the 18th century.

In 1961, a cornfield in Dorney was the scene of a nationally reported abduction. A lone gunman, James Hanratty, abducted Valerie Storie and Michael Gregsten and forced them at gunpoint to drive to a lay-by at Maulden in Bedfordshire, where he shot and murdered Gregsten, raped Storie and shot her. She survived, paralysed.

Topography
The village is on the north bank of the River Thames, on very gently sloping land towards the river and inchoate streams which were mostly joined into the Jubilee River, mainly on gravel-underlain soil.

Eton is 2.3 mi to the east. Slough, which is linked by two roads forming a rectangle with Dorney, is 3.7 mi east-northeast.

Major rowing events take place at Dorney Lake, including the 2012 Summer Olympics and annual events such as the Wallingford, Marlow and Metropolitan Regattas. The Olympics also hosted canoeing events there, which continue to take place occasionally.

In the south-east, Dorney Common is a large traditional grassed common, roughly triangular, which is a Site of Special Scientific Interest. Owing to the continued use of the land for grazing, the common has panoramic views of Windsor Castle two and a half miles to the east.

Local administration
Dorney's civil parish council covers minor upkeep, community events and recreational matters. Dorney is surrounded to the south, east and west by the non-metropolitan county of Berkshire, with a narrow border along its north (with Taplow and Burnham) further towards the heart of Buckinghamshire. This anomaly makes Dorney a salient, which dates to the Local Government Act 1972, which came into force on 1 April 1974; the village had been originally included in Berkshire in the related Bill, but an amendment to keep it in Buckinghamshire was proposed by local MP Ronald Bell and accepted by the government.

Features
There are 15 listed buildings in Dorney.

The village church's chancel and nave date from the 12th century, the tower was built about 1540, and the north chapel and porch were added in the 17th century. Restoration work in the 19th century somewhat obscured its medieval decoration.

Dorneywood country house takes its name from the parish, although is just over its northeastern border. It is used as a home (and entertainment or state reception venue) for a senior member of the UK government, usually a Secretary of State or other minister.

Transport
The village has no railway station. A regular bus timetable operates to Windsor and Slough.

The village is partly bounded by the north by the M4 motorway, where there is a junction just after the road north from the village meets the A4 Bath Road for Slough 'West'. This provides access to Heathrow Airport and London, and has meant that since the road's construction, Dorney has been accessible to commuters from both London and the Thames Valley..

Religion
A majority of the inhabitants in 2011 (62.8%) described themselves as Christian. The sole parish church is Anglican and is dedicated to Saint James. More than 2% of the population are Hindu, Muslim, Jewish or Buddhist.

Localities
In the parish of Dorney are the hamlets of Dorney Reach and Lake End; none centred more than 1 mi apart.

Dorney Reach
Dorney Reach is a community on a riverside road, almost half of the homes of which are by the River Thames, overlooking Monkey Island. This side of the river is also the location of Bray Lock; its name is somewhat of a misnomer, as the village of Bray sits on the opposite side of the river from the lock.

Lake End
Lake End includes the Pineapple pub and is the only settled part north of the Jubilee River on the main northward road from the village. It has a public car park by the Jubilee River which enables access to its towpath and the buildings of Dorney and Lake End.

Nearest places

 * Burnham — 2 miles
 * Taplow — 2 miles
 * Eton — 2 miles
 * Maidenhead — 4 miles

title: Dorney


text:
Sarcelles

Sarcelles is a commune in the northern suburbs of Paris, France. It is located 16.3 km from the centre of Paris. Sarcelles is a sub-prefecture of the Val-d'Oise department and the seat of the arrondissement of Sarcelles.

In the south of the commune, during the 1950s and 1960s, vast housing estates were built in order to accommodate pieds-noirs (French settlers from Algeria) and Jews who had left Algeria due to its war of independence. A few Jews from Egypt settled there after the Suez crisis, and Jews from Tunisia and Morocco settled in Sarcelles after unrest and riots against Jews due to the Six-Day War and the Yom Kippur War.

Transport
Sarcelles is served by Garges–Sarcelles station on Paris RER line D.

It is also served by Sarcelles–Saint-Brice station on the Transilien Paris-Nord suburban rail line. This station, although administratively located on the territory of the neighbouring commune of Saint-Brice-sous-Forêt, lies in fact very near the town centre of Sarcelles.

Population
the commune has about 40,000 residents from 40 backgrounds.

Immigration
A substantial number of inhabitants of the town are pieds-noirs from Northwest Africa who immigrated to France in the 1960s. Sarcelles is also home to a vibrant Jewish community and the largest concentration of Assyrians in France.

Rahsaan Maxwell, author of Ethnic Minority Migrants in Britain and France: Integration Trade-Offs, stated that compared with other French communities, the ethnic minorities in Sarcelles have more influence, so therefore "Sarcelles should not be considered representative of cities across metropolitan France". Residents believe that there is a "Sarcelles identity," meaning any ethnic group can be a part of the city, and they believe it lowers levels of crime and violence.

Compared with other parts of France, ethnic minorities in Sarcelles gained political power at a faster rate, with gains made in the 1980s instead of the 1990s and 2000s. Many politicians responded to minority demands sooner as many immigrants, especially Caribbeans and Sephardic Jews, had French citizenship. François Pupponi, the mayor in the 2000s dedicated monuments commemorating the histories of ethnic groups, authorised funding of organisations supporting specific ethnic groups such as running Arabic and Hindi language classes and permitted the use of public facilities for religious events. Pupponi argued that this style is the best method of giving many ethnic groups one sense of community. Critics argued that funding groups catering to specific ethnic groups promotes segregation.

Caribbeans
, 8.7% of the population was of Caribbean origin. , many of the ethnic Caribbean residents have French citizenship.

By the 1970s, Afro-Caribbeans became more interested in changing politics. By the 1980s, Guy Guyoubli, a local activist, organised an almost all-Caribbean protest list. Maxwell wrote that this demonstrated that Caribbeans had serious intentions of participating in the political system, even though there were no representatives elected from the lists. At the time, ethnic minorities across Metropolitan France were increasingly trying to influence the political system. The city's first ever two Caribbean councillors were elected in 1989. Around 1989, Raymond Lamontagne, the mayor, opened Metropolitan France's first ever Caribbean-orientated, council-funded community centre.

Maghrebian Muslims
In the 1950s and 1960s, Maghrebians began to arrive in Sarcelles. They developed political organisation in subsequent decades. Originally, the Muslims worshipped in converted makeshift areas, but, later, they built mosques for their community.

In the 1990s, Maghrebians were first elected to the commune council. Maxwell wrote that Maghrebians did not begin to obtain "key positions" until about 2012, as they had had "low turnout and weak community organisations".

Syriac Christians
A memorial to Assyro-Chaldean victims of the 1915 Assyrian genocide was dedicated in 2005. Part of the film The Last Assyrians features the Assyrian and Chaldean community.

Maghrebi Jews
During the 1960s, many Maghrebi Jews migrated to France, settling in Sarcelles. They were chiefly from Algeria, Tunisia and Morocco. Today, most of the Jewish residents have French citizenship.

During the peak immigration of Maghrebi Jews, they subscribed to a belief in assimilation and secularism. They had the North African belief of what Michel Wieviorka and Philippe Bataille, authors of The Lure of Anti-Semitism: Hatred of Jews in Present-Day France, describe as "a structuring role" that "does not cover all aspects of social life". Beginning in the 1980s, religion became more public and important. Wieviorka and Bataille stated that the previous North African practice is "becoming mixed up with the neo-Orthodox practices of the 'young people' for whom religion controls everything."

In 1983, a wave of councillors were elected who were Sephardic Jews from North Africa.

Crime
In 2012, Maxwell stated that "petty crime" and vandalism had become consistent issues. He said that "violent confrontations" among black migrants, Maghrebians, and Jews was "a recurring theme". He added that, by 2012, the commune had "developed a reputation as one of the more dangerous Paris suburbs." Maxwell wrote that local residents told him that the reputation was overblown.

Maxwell wrote that, during the 2005 French riots, a report concluded that the damage to buildings in Sarcelles was "relatively moderate". A later report concluded that, compared with most cities, Sarcelles had fewer days of severe riots. He also said that local residents characterised the damage as "not as bad as elsewhere and not as bad as one might have expected given Sarcelles's economic and ethnic profile."

Twin towns – sister cities
Sarcelles is twinned with:
 * 🇮🇱 Netanya, Israel, since 1988
 * 🇩🇪 Hattersheim, Germany, since 1987

Co-operation agreement

 * Martakert, Nagorno-Karabakh Republic, since 2015

Education
The commune has 19 public écoles maternelles (pre-schools/nurseries), 21 public écoles primaires (primary schools), six public collèges (junior high schools), two public lycées (senior high schools/sixth-form colleges), and two other educational institutions.
 * Collèges: Chantereine, Anatole-France, Évariste-Galois, Jean-Lurçat, Victor Hugo, and Voltaire
 * Lycées: Lycée Polyvalent de La Tourelle and Lycée Polyvalent J.J. Rousseau
 * Others: I.U.T (Institut universitaire de technologie), C.I.O (Centre d'information et d'orientation)

The Bibliothèque intercommunale Anna Langfus is located in Sarcelles. This library has over 60,000 items and is divided between an adults' section and a children's section. In addition the Espace Musique Mel Bonis is in Sarcelles.

Notable people

 * Les Twins, New Style dancers
 * Jonathan Assous, footballer
 * Damien Cely, diver
 * Sarah Cysique, judoka
 * Mohamed Dia, fashion designer
 * Didier Domi, footballer
 * Andy Faustin, footballer
 * Mathys Tel, footballer
 * Dimitri Foulquier, footballer
 * Eric Sabin, footballer
 * Derek Mazou-Sacko, footballer
 * Younousse Sankhare, footballer
 * Jean-Manuel Thetis, footballer
 * Frederic Thomas, footballer
 * Jonathan Tokple, footballer
 * Steeve Yago, footballer
 * Riyad Mahrez, footballer
 * Wissam Ben Yedder, footballer
 * Amir Haddad, singer
 * Miss Dominique, singer
 * Dominique Strauss-Kahn, former mayor of Sarcelles

title: Sarcelles


text:
Computational learning theory

In computer science, computational learning theory (or just learning theory) is a subfield of artificial intelligence devoted to studying the design and analysis of machine learning algorithms.

Overview
Theoretical results in machine learning mainly deal with a type of inductive learning called supervised learning. In supervised learning, an algorithm is given samples that are labeled in some useful way. For example, the samples might be descriptions of mushrooms, and the labels could be whether or not the mushrooms are edible. The algorithm takes these previously labeled samples and uses them to induce a classifier. This classifier is a function that assigns labels to samples, including samples that have not been seen previously by the algorithm. The goal of the supervised learning algorithm is to optimize some measure of performance such as minimizing the number of mistakes made on new samples.

In addition to performance bounds, computational learning theory studies the time complexity and feasibility of learning. In computational learning theory, a computation is considered feasible if it can be done in polynomial time. There are two kinds of time complexity results:

 * Positive results – Showing that a certain class of functions is learnable in polynomial time.
 * Negative results – Showing that certain classes cannot be learned in polynomial time.

Negative results often rely on commonly believed, but yet unproven assumptions, such as:

 * Computational complexity – P ≠ NP (the P versus NP problem);
 * Cryptographic – One-way functions exist.

There are several different approaches to computational learning theory based on making different assumptions about the inference principles used to generalise from limited data. This includes different definitions of probability (see frequency probability, Bayesian probability) and different assumptions on the generation of samples. The different approaches include:

 * Exact learning, proposed by Dana Angluin;
 * Probably approximately correct learning (PAC learning), proposed by Leslie Valiant;
 * VC theory, proposed by Vladimir Vapnik and Alexey Chervonenkis;
 * Inductive inference as developed by Ray Solomonoff;
 * Algorithmic learning theory, from the work of E. Mark Gold;
 * Online machine learning, from the work of Nick Littlestone.

While its primary goal is to understand learning abstractly, computational learning theory has led to the development of practical algorithms. For example, PAC theory inspired boosting, VC theory led to support vector machines, and Bayesian inference led to belief networks.

Surveys

 * Angluin, D. 1992. Computational learning theory: Survey and selected bibliography. In Proceedings of the Twenty-Fourth Annual ACM Symposium on Theory of Computing (May 1992), pages 351–369. http://portal.acm.org/citation.cfm?id=129712.129746
 * D. Haussler. Probably approximately correct learning. In AAAI-90 Proceedings of the Eight National Conference on Artificial Intelligence, Boston, MA, pages 1101–1108. American Association for Artificial Intelligence, 1990. http://citeseer.ist.psu.edu/haussler90probably.html

Feature selection

 * A. Dhagat and L. Hellerstein, "PAC learning with irrelevant attributes", in 'Proceedings of the IEEE Symp. on Foundation of Computer Science', 1994. http://citeseer.ist.psu.edu/dhagat94pac.html

Optimal O notation learning

 * Oded Goldreich, Dana Ron. On universal learning algorithms. http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.47.2224

Negative results

 * M. Kearns and Leslie Valiant. 1989. Cryptographic limitations on learning boolean formulae and finite automata. In Proceedings of the 21st Annual ACM Symposium on Theory of Computing, pages 433–444, New York. ACM. http://citeseer.ist.psu.edu/kearns89cryptographic.html

Error tolerance

 * Michael Kearns and Ming Li. Learning in the presence of malicious errors. SIAM Journal on Computing, 22(4):807–837, August 1993. http://citeseer.ist.psu.edu/kearns93learning.html
 * Kearns, M. (1993). Efficient noise-tolerant learning from statistical queries. In Proceedings of the Twenty-Fifth Annual ACM Symposium on Theory of Computing, pages 392–401. http://citeseer.ist.psu.edu/kearns93efficient.html

Equivalence

 * D.Haussler, M.Kearns, N.Littlestone and M. Warmuth, Equivalence of models for polynomial learnability, Proc. 1st ACM Workshop on Computational Learning Theory, (1988) 42-55.

title: Computational learning theory