Plasma chemistry of iodine atoms production for CW oxygen-iodine laser

Influence of molecular oxygen on iodine atoms production in an RF discharge

“…The iodine atoms number density achieved in the present experiments turned out to be twice as large as in our previous experiments [11] when we used the discharge chamber with bare plane aluminum electrodes. As shown in figure 4, for the Ar carrier, unlike in [11], the addition of oxygen at 100 W discharge power input clearly had an advantageous effect on iodine production, increasing [I] by up to 35%. In our opinion the reason for the difference of the present results and the previous results [11] is the better homogeneity of the discharge in the quartz tubes.…”

“…For the He carrier, again as in [11], the addition of oxygen had the same effect on iodine dissociation, as depicted in figure 5. Analogous to the experiments with the Ar carrier, the addition of oxygen at 200 W discharge power input exhibited a most profound effect on iodine extraction increasing [I] up to ~75% at small CH 3 I flow rates and ~50% at large flow rates.…”

“…As shown in figure 4, for the Ar carrier, unlike in [11], the addition of oxygen at 100 W discharge power input clearly had an advantageous effect on iodine production, increasing [I] by up to 35%. In our opinion the reason for the difference of the present results and the previous results [11] is the better homogeneity of the discharge in the quartz tubes. In the present experiments at 100 W discharge power with an increase of CH 3 I flow rate, the discharge size along the flow decreased and at the largest flow rate of 0.16 mmol s −1 the discharge size was almost twice as short.…”

“…In our earlier experiments with a DC discharge [15], contamination of electrodes by products of CH 3 I dissociation was a serious problem, because the discharge eventually became unstable and the electrodes needed cleaning. An RF discharge with bare planar aluminum electrodes had shown much better results as it turned out to be absolutely insensitive to the contamination of electrodes [11], presumably because the discharge operated in α-mode. However, planar configuration also suffered from discharge inhomogeneity in mixtures with large CH 3 I content.…”

“…Also, products of CH 3 I dissociation form soot that contaminates electrodes and makes a diffuse dc discharge impossible after a few minutes of operation. RF discharge easily resolved this problem as it proved to be capable of operating at sufficiently high pressures of tens of Torr and to be immune to the contamination of electrodes [11]. However, RF discharge between uncoated parallel alumina plates, like in [11], tended to contract with an increase of discharge power and with CH 3 I flow rate; therefore, the design of the discharge chamber had to be improved.…”