Argon flash

Last updated December 20, 2023

Argon flash, also known as argon bomb, argon flash bomb, argon candle, and argon light source, is a single-use source of very short and extremely bright flashes of light. The light is generated by a shock wave in argon or, less commonly, another noble gas. The shock wave is usually produced by an explosion. Argon flash devices are almost exclusively used for photographing explosions and shock waves.

Process

The light generated by an explosion is produced primarily by compression heating of the surrounding air. Replacement of the air with a noble gas considerably increases the light output; with molecular gases, the energy is consumed partially by dissociation and other processes, while noble gases are monatomic and can only undergo ionization; the ionized gas then produces the light. The low specific heat capacity of noble gases allows heating to higher temperatures, yielding brighter emission.^[1] Flashtubes are filled with noble gases for the same reason.

Engineering

Typical argon flash devices consist of an argon-filled cardboard or plastic tube with a transparent window on one end and an explosive charge on the other end. Many explosives can be used; Composition B, PETN, RDX, and plastic bonded explosives are just a few examples.

The device consists of a vessel filled with argon and a solid explosive charge. The explosion generates a shock wave, which heats the gas to very high temperature (over 10⁴ K; published values vary between 15,000 K to 30,000 K with the best values around 25,000 K^[1]). The gas becomes incandescent and emits a flash of intense visible and ultraviolet black-body radiation. The emission for the temperature range is highest between 97–193 nm, but usually only the visible and near-ultraviolet ranges are exploited.

To achieve emission, the layer of at least one or two optical depths of the gas has to be compressed to sufficient temperature. The light intensity rises to full magnitude in about 0.1 microsecond. For about 0.5 microsecond the shock wave front instabilities are sufficient to create significant striations in the produced light; this effect diminishes as the thickness of the compressed layer increases. Only an about 75 micrometer thick layer of the gas is responsible for the light emission. The shock wave reflects after reaching the window at the end of the tube; this yields a brief increase of light intensity. The intensity then fades.^[1]

The amount of explosive can control the intensity of the shock wave and therefore of the flash. The intensity of the flash can be increased and its duration decreased by reflecting the shock wave by a suitable obstacle; a foil or a curved glass can be used.^[2] The duration of the flash is about as long as the explosion itself, depending on the construction of the lamp, between 0.1 and 100 microseconds.^[3] The duration is dependent on the length of the shockwave path through the gas, which is proportional to the length of the tube; it was shown that each centimeter of the path of shock wave through the argon medium is equivalent to 2 microseconds.^[4]

Uses

Argon flash is a standard procedure for high-speed photography, especially for photographing explosions,^[5] or less commonly for use in high altitude test vehicles.^[6] The photography of explosions and shock waves is made easy by the fact that the detonation of the argon flash lamp charge can be accurately timed relative to the test specimen explosion and the light intensity can overpower the light generated by the explosion itself. The formation of shock waves during explosions of shaped charges can be imaged this way.

As the amount of released radiant energy is fairly high, significant heating of the illuminated object can occur. Especially in the case of high explosives, this has to be taken into account.

Super Radiant Light (SRL) sources are an alternative to argon flash. An electron beam source delivers a brief and intense pulse of electrons to suitable crystals (e.g. doped cadmium sulfide). Flash times in the nanosecond to picosecond range are achievable. Pulsed lasers are another alternative.^[4]

Related Research Articles

The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications.

In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. This includes:

Sonoluminescence is the emission of light from imploding bubbles in a liquid when excited by sound.

In astronomy, the interstellar medium (ISM) is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space. The energy that occupies the same volume, in the form of electromagnetic radiation, is the interstellar radiation field. Although the density of atoms in the ISM is usually far below that in the best laboratory vacuums, the mean free path between collisions is short compared to typical interstellar lengths, so on these scales the ISM behaves as a gas (more precisely, as a plasma: it is everywhere at least slightly ionized), responding to pressure forces, and not as a collection of non-interacting particles.

In physics, a shock wave, or shock, is a type of propagating disturbance that moves faster than the local speed of sound in the medium. Like an ordinary wave, a shock wave carries energy and can propagate through a medium but is characterized by an abrupt, nearly discontinuous, change in pressure, temperature, and density of the medium.

<span class="mw-page-title-main">Effects of nuclear explosions</span> Type and severity of damage caused by nuclear weapons

The effects of a nuclear explosion on its immediate vicinity are typically much more destructive and multifaceted than those caused by conventional explosives. In most cases, the energy released from a nuclear weapon detonated within the lower atmosphere can be approximately divided into four basic categories:

<span class="mw-page-title-main">Strobe light</span> Device producing regular flashes of light

A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Ancient Greek στρόβος (stróbos), meaning "act of whirling".

<span class="mw-page-title-main">Neon sign</span> Electrified, luminous tube lights

In the signage industry, neon signs are electric signs lighted by long luminous gas-discharge tubes that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in December 1910 by Georges Claude at the Paris Motor Show. While they are used worldwide, neon signs were popular in the United States from about the 1920s to 1950s. The installations in Times Square, many originally designed by Douglas Leigh, were famed, and there were nearly 2,000 small shops producing neon signs by 1940. In addition to signage, neon lighting is used frequently by artists and architects, and in plasma display panels and televisions. The signage industry has declined in the past several decades, and cities are now concerned with preserving and restoring their antique neon signs.

The exploding-bridgewire detonator is a type of detonator used to initiate the detonation reaction in explosive materials, similar to a blasting cap because it is fired using an electric current. EBWs use a different physical mechanism than blasting caps, using more electricity delivered much more rapidly. Exploding with more precise timing after the electric current is applied, by the process of exploding wire method. This has led to their common use in nuclear weapons.

<span class="mw-page-title-main">Flashtube</span> Incoherent light source

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.

The shock tube is an instrument used to replicate and direct blast waves at a sensor or a model in order to simulate actual explosions and their effects, usually on a smaller scale. Shock tubes can also be used to study aerodynamic flow under a wide range of temperatures and pressures that are difficult to obtain in other types of testing facilities. Shock tubes are also used to investigate compressible flow phenomena and gas phase combustion reactions. More recently, shock tubes have been used in biomedical research to study how biological specimens are affected by blast waves.

<span class="mw-page-title-main">High voltage</span> Electrical potential which is large enough to cause damage or injury

High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, high voltage refers to voltage above a certain threshold. Equipment and conductors that carry high voltage warrant special safety requirements and procedures.

<span class="mw-page-title-main">Rope trick effect</span> "Spikes" emanating from suspended nuclear explosions

Rope trick is the term given by physicist John Malik to the curious lines and spikes which emanate from the fireball of certain nuclear explosions just after detonation.

Inductively coupled plasma atomic emission spectroscopy (ICP-AES), also referred to as inductively coupled plasma optical emission spectroscopy (ICP-OES), is an analytical technique used for the detection of chemical elements. It is a type of emission spectroscopy that uses the inductively coupled plasma to produce excited atoms and ions that emit electromagnetic radiation at wavelengths characteristic of a particular element. The plasma is a high temperature source of ionised source gas. The plasma is sustained and maintained by inductive coupling from electrical coils at megahertz frequencies. The source temperature is in the range from 6000 to 10,000 K. The intensity of the emissions from various wavelengths of light are proportional to the concentrations of the elements within the sample.

An infrared heater or heat lamp is a heating appliance containing a high-temperature emitter that transfers energy to a cooler object through electromagnetic radiation. Depending on the temperature of the emitter, the wavelength of the peak of the infrared radiation ranges from 750 nm to 1 mm. No contact or medium between the emitter and cool object is needed for the energy transfer. Infrared heaters can be operated in vacuum or atmosphere.

Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample. The wavelength of the atomic spectral line in the emission spectrum gives the identity of the element while the intensity of the emitted light is proportional to the number of atoms of the element. The sample may be excited by various methods.

Sonoluminescence is a phenomenon that occurs when a small gas bubble is acoustically suspended and periodically driven in a liquid solution at ultrasonic frequencies, resulting in bubble collapse, cavitation, and light emission. The thermal energy that is released from the bubble collapse is so great that it can cause weak light emission. The mechanism of the light emission remains uncertain, but some of the current theories, which are categorized under either thermal or electrical processes, are Bremsstrahlung radiation, argon rectification hypothesis, and hot spot. Some researchers are beginning to favor thermal process explanations as temperature differences have consistently been observed with different methods of spectral analysis. In order to understand the light emission mechanism, it is important to know what is happening in the bubble's interior and at the bubble's surface.

The exploding wire method or EWM is a way to generate plasma that consists in sending a strong enough pulse of electric current through a thin wire of some electrically conductive material. The resistive heating vaporizes the wire, and an electric arc through that vapor creates an explosive shockwave.

<span class="mw-page-title-main">Heating film</span>

Heating films are a method of electric resistance heating, providing relatively low temperatures over large areas. Heating films can be directly installed to provide underfloor heating, wall radiant heating and ceiling radiant heating.

References

1 2 3 4 Explosive-driven shock waves in argon, William C. Davis, Terry R. Salyer, Scott I. Jackson, and Tariq D. Aslam, Los Alamos National Laboratory
↑ Rudolf Meyer; Josef Köhler; Axel Homburg (2007). Explosives. Wiley-VCH. p. 21. ISBN 978-3-527-31656-4. Argon flash.
↑ Sidney F. Ray (1999). Scientific photography and applied imaging. Focal Press. p. 445. ISBN 0-240-51323-1.
1 2 Lalit C. Chhabildas; Lee Davison; Yasuyuki Horie (2005). High-pressure shock compression of solids VIII: the science and technology of high-velocity impact. Springer. p. 263. ISBN 3-540-22866-7.
↑ "Argon flash (Arno Hahma)". Yarchive.net. 1999-01-29. Retrieved 2010-03-23.
↑ Todd Jr, J; Parsons, D (1957-01-11). "Technical Report: High-Explosive Argon Flash Light Source". Osti.gov. doi: 10.2172/4310914 . OSTI 4310914.

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.

[intdet-1] 1 2 3 4 Explosive-driven shock waves in argon, William C. Davis, Terry R. Salyer, Scott I. Jackson, and Tariq D. Aslam, Los Alamos National Laboratory

[2] Rudolf Meyer; Josef Köhler; Axel Homburg (2007). Explosives. Wiley-VCH. p. 21. ISBN 978-3-527-31656-4. Argon flash.

[3] Sidney F. Ray (1999). Scientific photography and applied imaging. Focal Press. p. 445. ISBN 0-240-51323-1.

[r1-4] 1 2 Lalit C. Chhabildas; Lee Davison; Yasuyuki Horie (2005). High-pressure shock compression of solids VIII: the science and technology of high-velocity impact. Springer. p. 263. ISBN 3-540-22866-7.

[5] "Argon flash (Arno Hahma)". Yarchive.net. 1999-01-29. Retrieved 2010-03-23.

[6] Todd Jr, J; Parsons, D (1957-01-11). "Technical Report: High-Explosive Argon Flash Light Source". Osti.gov. doi: 10.2172/4310914 . OSTI 4310914.

[1]

[2]

[3]

[4]

[5]

[6]