Information about Xenon Flash Lamp
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Xenon flash lamp being fired. (See below for animated version)
A xenon flash lamp is an electric glow discharge lamp designed to produce extremely intense, incoherent, full-spectrum white light for very short durations.
Construction
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U-shaped Xenon Flash Lamp
The lamp comprises a sealed tube, often made of fused quartz, which is filled with a mixture of gases, primarily xenon, and electrodes to carry electrical current to the gas mixture. Additionally, a high voltage power source is necessary to energize the gas mixture; this high voltage is usually stored on a capacitor so as to allow very speedy delivery of very high electrical current when the lamp is triggered.
The glass envelope is most commonly a thin tube, 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'). The electrodes protrude into each end of the tube, and are connected to a capacitor that is charged to a relatively high voltage. This is usually between 250 and 2000 volts, depending on the length of the tube, and the specific gas mixture.
Operation
A flash is initiated by first ionizing the gas mixture, then sending a very large pulse of current through the ionized gas. Ionization is necessary to decrease the electrical resistance of the gas so that a pulse measuring as much as thousands of amperes can travel through the tube. The initial ionization pulse may be generated by a tesla coil. A short high voltage peak produces the first ions at the sharp tip of the cathode (the housing is grounded). By applying radio frequency voltage the ions do not need to reach the anode, but couple capacitively to the housing (and the anode). This may be enhanced by putting a metal band onto the glass or a wire that is wrapped around the glass tube or by using water cooling, since water has a high dielectric constant and if ionized also conducts. When this current pulse travels through the tube, it excites electrons surrounding the xenon atoms causing them to jump to higher energy levels. The atoms' electrons immediately drop back to a lower orbit, producing photons in the process. Depending on the size and application of the flashlamp, xenon fill pressures may range from a few kilopascals to tens of kilopascals (0.01–0.1 atmosphere or tens to hundreds of torr). For low electrode wear the electrode needs to be at high temperature for the thermionic emission of electrons.Output spectrum
As with all ionized gases, xenon flash lamps emit light in various spectral lines. This is the same phenomenon that gives neon signs their characteristic color. However, for xenon, there are enough spectral lines, and they are distributed across the spectrum in such a way, that to the human eye the light appears mostly white. The spectral profile of a xenon arc peaks in the green range, which is well matched to many applications involving visible light. This is the primary motivation for selecting xenon as a filler in spite of its high cost; krypton is also occasionally used, although it is even more expensive. Krypton has much greater output in the near-IR range, which is better matched to the absorption profile of Nd:YAG laser media than xenon emissions.During normal operation in most photographic-type systems, the spectral component of a flashlamp's emission is overshadowed by blackbody radiation. The proportion of light produced by spectral action compared to thermal action depends on current density in the arc. Higher current densities favor blackbody radiation over spectral radiation. For this reason, many laser systems intentionally utilize lower current densities than photographic flashes since more narrow spectral lines are usually favorable for pumping lasers, while a broadband output is better for photographic purposes. Production of greenish blue light instead of pure white is a clear indication of low-current density operation.
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The flashlamps used on the National Ignition Facility laser are truly massive, the largest ever in commercial production.
Intensity and duration of flash
For short pulses the number of emitted electrons from the cathode is the limit. For longer pulses or continuous operation the cooling is the limit. Discharge durations for common flashlamps are in the microsecond to a few milliseconds range and can have repetition rates of hundreds of hertz.The flash that emanates from a xenon flash lamp 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.[1] 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.
Applications
Because the duration of the flash that is emitted by a xenon flash tube can be accurately controlled, and due to the high intensity of the light, xenon flash lamps are most commonly used as photographic strobe lights. Xenon flashlamps are also used in the technique of very high speed or "stop-motion" photography, which was pioneered by Harold Edgerton in the 1930s.Due to their high-intensity and relative brightness at short wavelengths (extending into the ultraviolet) and short pulsewidths, flashlamps are also ideally suited as light sources for pumping atoms in a laser to excited states where they can subsequently be stimulated to emit coherent monochromatic light. Proper selection of the filler gas is crucial here, so the maximum of radiated output energy is concentrated in the bands that are the best absorbed by the lasing medium; eg. krypton flashlamps are more suitable than xenon flashlamps for pumping s, as krypton emission in near infrared is better matching to the absorption spectrum of Nd:YAG.
Xenon flash lamps 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 flash tubes is turned into useful laser light for this application.
Animation
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Xenon flash lamp being fired.
References
- Timing electronics can trigger multiple flashes and then activate a Q-switch
- Emission spectra of different flash lamps
See also
| Lighting and Lamps | ||
|---|---|---|
| Incandescent: | Conventional - Halogen - Parabolic aluminized reflector (PAR) | ){kind=spacer} |
| Fluorescent: | Compact fluorescent (CFL) - Linear fluorescent - Induction lamp | |
| Gas discharge: | High-intensity discharge (HID) - Mercury-vapor - Metal-halide - Neon - Sodium vapor | |
| Electric arc: | Arc lamp - HMI - Xenon arc - Yablochkov candle | |
| Combustion: | Acetylene/Carbide - Candle - Gas lighting - Kerosene lamp - Limelight - Oil lamp - Safety lamp | |
| Other types: | Sulfur lamp - Light-emitting diode (LED) - Fiber optics - Plasma | |
Electric glow discharge is a type of plasma formed by passing a current at 100 V to several kV through a gas, usually argon or another noble gas. It is found in products such as fluorescent lights and plasma-screen televisions, and is used in plasma physics and analytical chemistry.
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Coherence is the property of wave-like states that enables them to exhibit interference. It is also the parameter that quantifies the quality of the interference (also known as the degree of coherence).
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Xenon (IPA: /ˈzɛnɒn, ˈziːnɒn/) is a chemical element that has the symbol Xe and atomic number 54.
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capacitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity,
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Electric current is the flow (movement) of electric charge. The SI unit of electric current is the ampere (A), which is equal to a flow of one coulomb of charge per second.
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Definition
The amount of electric current (measured in amperes) through some surface, e.g...... Click the link for more information.
photographic lens (also known as objective lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image
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Photography [fә'tɑgrәfi:],[foʊ'tɑgrәfi:] is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or electronic sensor.
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capacitor is an electrical/electronic device that can store energy in the electric field between a pair of conductors (called "plates"). The process of storing energy in the capacitor is known as "charging", and involves electric charges of equal magnitude, but opposite polarity,
..... Click the link for more information.
..... Click the link for more information.
volt (symbol: V) is the SI derived unit of electric potential difference or electromotive force.[1][2] It is named in honor of the Italian physicist Alessandro Volta (1745–1827), who invented the voltaic pile, the first modern chemical battery.
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ion is an atom or molecule which has lost or gained one or more electrons, making it positively or negatively charged. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion
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Pulsed power is the term used to describe the science and technology of accumulating energy over a relatively long period of time and releasing it very quickly thus increasing the instantaneous power.
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Electrical resistance is a measure of the degree to which an object opposes an electric current through it. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance measured in siemens.
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ampere, in practice often shortened to amp, (symbol: A) is a unit of electric current, or amount of electric charge per second. The ampere is an SI base unit, and is named after André-Marie Ampère, one of the main discoverers of electromagnetism.
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Tesla coil (also teslacoil) is a type of resonant transformer, named after its inventor, Nikola Tesla. Tesla coils consist of two, or sometimes three, coupled resonant electric circuits.
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Field emission, also known as Fowler-Nordheim tunneling, is a form of quantum tunneling in which electrons pass through a barrier in the presence of a high electric field.
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A cathode is an electrode through which (positive) electric current flows out of a polarized electrical device. Mnemonic: CCD (Cathode Current Departs). To dispel a common misconception, often incorrectly inferred from the correct fact that in all electrochemical
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Radio frequency, or RF, is a frequency or rate of oscillation within the range of about 3 Hz and 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves.
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The relative static permittivity (or static relative permittivity) of a material under given conditions is a measure of the extent to which it concentrates electrostatic lines of flux.
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Electron
Theoretical estimates of the electron density for the first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Composition: Elementary particle
Family: Fermion
Group: Lepton
Generation: First
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Theoretical estimates of the electron density for the first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Composition: Elementary particle
Family: Fermion
Group: Lepton
Generation: First
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The pascal (symbol: Pa) is the SI derived unit of pressure or stress (also: Young's modulus and tensile strength). It is a measure of perpendicular force per unit area i.e. equivalent to one newton per square meter or one Joule per cubic meter.
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Standard atmosphere is a pressure defined as 101 325 Pa and used as unit of pressure (symbol: atm). Standard atmosphere is a non-SI unit that is internationally recognized.
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torr (symbol: Torr) is a non-SI unit of pressure defined as 1/760 of an atmosphere. It was named after Evangelista Torricelli, an Italian physicist and mathematician who discovered the principle of the barometer in 1644.
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Thermionic emission (archaically known as the Edison effect) is the flow of charged particles called thermions from a charged metal or a charged metal oxide surface, caused by thermal vibrational energy overcoming the electrostatic forces holding electrons to the
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spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies.
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Neon signs are luminous-tube signs that contain neon or other inert gases at a low pressure. Applying a high voltage (usually a few thousand volts) makes the gas glow brightly. They are produced by the craft of bending glass tubing into shapes.
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White is the combination of all the colors of the visible light spectrum.[1]. It is sometimes described as an achromatic color, like black.
White is technically achromatic, and not a color, since it has no hue.
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White is technically achromatic, and not a color, since it has no hue.
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KRYPTON is a frame-based computer programming language.
"An Essential Hybrid Reasoning System: Knowledge and Symbol Level Accounts of KRYPTON", R.J. Brachman et al, Proc IJCAI-85, 1985 [1] .
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"An Essential Hybrid Reasoning System: Knowledge and Symbol Level Accounts of KRYPTON", R.J. Brachman et al, Proc IJCAI-85, 1985 [1] .
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To help compare orders of magnitude of different times this page lists times between 10−6 seconds and 10−5 seconds (1 microsecond to 10 microseconds). A microsecond is one millionth of a second.
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To help compare orders of magnitude of different times this page lists times between 10−3 seconds and 10−2 seconds (1 millisecond to 10 milliseconds). A millisecond (ms) is one thousandth of a second.
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hertz (symbol: Hz) is the SI unit of frequency. Its base unit is cycle/s or s-1 (also called inverse seconds, reciprocal seconds). In English, hertz is used as both singular and plural.
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