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Chemical laser

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Title: Chemical laser  
Author: World Heritage Encyclopedia
Language: English
Subject: Directed-energy weapon, ElectricOIL, All gas-phase iodine laser, Hydrogen fluoride laser, Tactical High Energy Laser
Collection: American Inventions, Chemical Lasers
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Chemical laser

A chemical laser is a laser that obtains its energy from a chemical reaction. Chemical lasers can reach continuous wave output with power reaching to megawatt levels. They are used in industry for cutting and drilling.

Common examples of chemical lasers are the chemical oxygen iodine laser (COIL), all gas-phase iodine laser (AGIL), and the hydrogen fluoride (HF) and deuterium fluoride (DF) lasers, both operating in the mid-infrared region. There is also a DF–CO2 laser (deuterium fluoridecarbon dioxide), which, like COIL, is a "transfer laser." The HF and DF lasers are unusual, in that there are several molecular energy transitions with sufficient energy to cross the threshold required for lasing. Since the molecules do not collide frequently enough to re-distribute the energy, several of these laser modes operate either simultaneously, or in extremely rapid succession, so that an HF or DF laser appears to operate simultaneously on several wavelengths unless a wavelength selection device is incorporated into the resonator.

Origin of the CW chemical HF/DF laser

The possibility of the creation of infrared lasers based on the vibrationally excited products of a chemical reaction was first proposed by

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References

Despite the performance advantages of chemical lasers, the Department of Defense stopped all development of chemical laser systems with the termination of the Airborne Laser Testbed in 2012. The desire for a "renewable" power source, i.e. not having to supply unusual chemicals like fluorine, deuterium, basic hydrogen-peroxide, or iodine, led the DoD to push for electrically pumped lasers such as diode pumped alkali lasers (DPALS).[18]

TRW also produced a cylindrical chemical laser (the Alpha laser) for DARPA, which had the advantage, at least on paper, of being scalable to even larger powers. However, by 1990, the interest in chemical lasers had shifted toward shorter wavelengths, and the chemical oxygen-iodine laser (COIL) gained the most interest, producing radiation at 1.315 μm. There is a further advantage that the COIL laser generally produces single wavelength radiation, which is very helpful for forming a very well focused beam. This type of COIL laser is used today in the ABL (Airborne Laser, the laser itself being built by Northrop Grumman) and in the ATL (Advanced Tactical Laser) produced by Boeing. Meanwhile, a lower power HF laser was used for the THEL (Tactical High Energy Laser) built in the late 1990s for the Israeli Ministry of Defense in cooperation with the U.S. Army SMDC. It holds the distinction of being the first fielded high energy laser to demonstrate effectiveness in fairly realistic tests against rockets and artillery. The MIRACL laser has demonstrated effectiveness against certain targets flown in front of it at White Sands Missile Range, but it is not configured for actual service as a fielded weapon. ABL was successful in shooting down several full sized missiles from significant ranges, and ATL was successful in disabling moving land vehicles and other tactical targets.

The TRW Systems Group in Redondo Beach, California, subsequently received US Air Force contracts to build higher power CW HF/DF lasers. Using a scaled-up version of an Aerospace Corporation design, TRW achieved 100 kW power levels. General Electric, Pratt & Whitney, & Rocketdyne built various chemical lasers on company funds in anticipation of receiving DoD contracts to build even larger lasers. Only Rocketdyne received contracts of sufficient value to continue competing with TRW. TRW produced the MIRACL device for the U.S. Navy that achieved megawatt power levels. The latter is believed to be the highest power continuous laser, of any type, developed to date (2007).

The early analytical models coupled with chemical rate studies[14] led to the design of efficient experimental CW HF laser devices at United Aircraft,[15] and The Aerospace Corporation.[16] Power levels up to 10 kW were achieved. DF lasing was obtained by the substitution of D2 for H2. A group at United Aircraft Research Laboratories produced a re-circulating chemical laser,[17] which did not rely on the continuous consumption of chemical reactants.

Performance

Comprehensive chemical laser models were developed at SAIC by R. C. Wade,[10] at TRW by C.-C. Shih, [11] by D. Bullock and M. E. Lainhart,[12] and at Rocketdyne by D. A. Holmes and T. R. Waite.[13] Of these, perhaps the most sophisticated was the CROQ code at TRW, outpacing the early work at Aerospace Corporation.

Chemical lasers stimulated the use of wave-optics calculations for resonator analysis. This work was pioneered by E. A. Sziklas (TRW (now part of Northrop Grumman).

The analysis of the HF laser performance is complicated due to the need to simultaneously consider the fluid dynamic mixing of adjacent supersonic streams, multiple non-equilibrium chemical reactions and the interaction of the gain medium with the optical cavity. The researchers at The Aerospace Corporation developed the first exact analytic (flame sheet) solution,[5] the first numerical computer code solution[6] and the first simplified model[7] describing CW HF chemical laser performance.

The TRW) used a chemical reaction to provide the atomic fluorine, a concept included in the patent disclosure of Spencer et al.[4] The latter configuration obviated the need for electrical power and led to the development of high-power lasers for military applications.

. Although this work did not produce a purely chemical continuous wave laser, it paved the way by showing the viability of the chemical reaction as a pumping mechanism for a chemical laser. DF-CO2 transfer laser (DF) were demonstrated. Pimentel went on to explore a deuterium fluoride (HF) and hydrogen fluoride suitable for a laser. Then excited state so vigorously that the molecule disassociated and then re-combined, leaving it in an pumped optically (HCl) was hydrogen chloride First, [2]

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