Eur. Phys. J. D (2012) 66: 89
https://doi.org/10.1140/epjd/e2012-20655-x

Regular Article

Dissociation of molecular iodine in RF discharge for oxygen-iodine lasers

Institute of Physics, v.v.i, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague 8, Czech Republic

^a e-mail: jirasek@fzu.cz

Received: 11 November 2011
Received in final form: 11 February 2012
Published online: 19 April 2012

Abstract

The dissociation of molecular iodine in 40 MHz-RF discharge was studied experimentally. This generation of atomic iodine is aimed at use in oxygen-iodine lasers. The discharge was ignited in a mixture of I₂  +  buffer gas fast-flowing through the cylindrical chamber and the discharge products were injected into a supersonic flow of nitrogen. The atomic iodine number density was measured in a low-pressure cavity after mixing with nitrogen and the dissociation fraction was calculated related to the input I₂ flow rate. The dissociation fraction of 46.2% was achieved at 0.22 mmol/s of I₂ and 7 mmol/s of Ar and RF power of 500 W. Argon and helium were used as a buffer gas; discharge stability and dissociation efficiency were better with argon. At the I₂ flow rate corresponding to the operation of a 1 kW chemical oxygen-iodine laser, the dissociation fraction was about 20%. The dissociation efficiency (the fraction of absorbed energy used for the dissociation) significantly decreased with increasing in the specific energy. At a reasonable I₂ flow rate (0.32 mmol/s), the maximum achieved efficiency was 8.5% and the corresponding energy cost was 8.9 eV per dissociating of one I₂ molecule. The input energy of more than 3 kJ per 1 mmol of I₂ is needed for dissociating at least 50% of I₂. The obtained dependencies on the gas flow rates infer a good chance for scaling-up of the tested RF discharge generator for the intended application.