Study on the purification of hydrogen bromide gas by fractional distillation technique and its effect on improvement of copper–hydrogen bromide laser performance

Abstract

This paper presents a purification process of hydrogen bromide (HBr) gas by fractional distillation technique and its use for performance enhancement of copper-HBr laser (Cu-HBrL). The residual impurities in HBr were suppressed by a two-step distillation process at temperatures of −196°C and −20°C. The lowering of the impurities was confirmed by comparing the mass spectrograph of the HBr gas before and after distillation, using a quadrupole mass spectrometer. The effect of the purified HBr gas on the performance of Cu-HBrL average output power as well its electrical discharge characteristics were studied. More than 37% improvement in the laser average output power (40 to 55 W) was observed with the use of this distilled HBr gas compared to undistilled gas. The underlying mechanism of the enhancement was analyzed by comparing electrical discharge characteristics in the two cases. The improvement in Cu-HBrL performance with distilled HBr gas was attributed to lowering of bromine and hydrogen concentration, mainly manifested as increased average electrical energy coupling to the discharge. This resulted in increased laser gain as well as gain volume, which were reflected in increases in laser output power and beam diameter.

Studies on the spectral purity of copper–hydrogen bromide laser radiations

“…(4)-(7) for single emission line approximation. In a Cu-HBrL, the active medium composition during the lasing period would be considered to be dominated by a mixture of Ne, Cu, HBr, and its dissociation products, such as H and Br, owing to the fact that the CuBr molecule formed by reaction of Cu and HBr completely dissociates into Cu and Br [8,[33][34][35]. So it would be judicious to assume that with an initial HBr concentration of ∼2 mbar, the equilibrium concentration of gaseous species in the discharge during the lasing period would be ∼28 mbar of Ne, ∼1 mbar of HBr, ∼1 mbar of H, and ∼1 mbar of Br.…”

Gas Lasers

“…Another important laser in the class is gold vapour laser operating at red (628 nm) and UV (312 nm) spectrum. In Indian context, a mature technology development programme of high beam quality, high-power CVL exists [4][5][6][7][8][9][10] at RRCAT, Indore, for generation of high repetition rate UV and tunable visible laser radiations and their applications. Since this depopulation process is slow, CVL operation is only pulsed albeit at high repetition rates.…”