<title>Excimer laser with sealed x-ray preionizer</title>

Abstract

In this paper we present the description of X-ray preionized excimer laser. For this laser the special sealed metal-ceramic X-ray areionizer with cold cathode was constructed. The cathode was made from a carbon felt and had 4x80 cm area. The discharge volume was 70x4x3 cm3 and on XeCl one provided the energy up to 2 J in a pulse.In the same discharge chamber the different type of preionizers ( spark discharges, UV laser radiation) were investigated. It was shown that the output energy depends rather the electron density uniformity than the electron concentration.For the pulse energy of excimer laser increasing high uniformity discharge in large volume must be produced. In this case the demands upon discharge volume preionization are very strict. The main parameters of preionizer are the initial electrons density, it's uniformity and the preionizers action on the gas mixture life time.UV preionization by spark discharges produces high electron density ( -1010 cm3 ) . But in this system the electron density is not uniform because of hard UV-radiation high absorption and discreetly distribution of sparks. Beside the sparks produce impurities and this process diminishes the gas lifetime.UV preionization by laser source produces more uniform initial electron density on the level 108 cm3.2 But it's not convenient because it demands the use of low ionization additives or powerful external excimer laser.The use of X-ray preionization is the best decision of problem the excimer laser to large volume and energy scaling because of X-rays large penetrationIn this paper we present the description of X-ray preionized excimer laser and compare on the output laser parameters with the preionizers of another types. Fig. 1 shows the laser chamber with sealed metal-ceramic X-ray preionizer. The carbon cathode of X-ray preionizer has an area of 6x80 cm2 and is placed in the electrostatic screen. The anode is W-foil 5um thick cooling by water. The output window is manufactured from stainless steel 50 m thick. The X-ray preionizer was supplied by the electrostatic and getter vacuum pumps. Pressure inside the X-ray preionizer didn't exceed the value i08 Pa. The e-beam diode was fed by Marx generator with amplitude voltage up to 120 kY with risetime -100 ns.The laser chamber was constructed of polyamid and designed for gas pressure up to 6 atm. The laser electrodes were composed from two contoured shape electrodes. The flat electrodes were 80 x 40 cm2 sire. The electrode gap was 4 cm width.One electrode was milled down in center to 0.6 mm thick and was covered by Al foil 0.5mm thick. The cavity inside the electrode was filled by buffer gas at working pressure.The laser chamber windows were UV-quartz plates with antireflection coating. The plane parallel optical cavity was produced by 100 % reflectivity dielectric mirror and uncoated quartz plate as an output coupler. 0-8194-0612-0/91/$4.00 SPIE Vol. 1503 Excimer Lasers andApplications /11(1991) / 197 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/10/2015 Terms of Use: ...