Long Life Krypton Arc Lamp For Pumping Nd:Yag Lasers.

The objective of this program was to develop a CW krypton are lamp with which to pump a 6 mm x 50 mm NdYAG laser rod to 100 watts laser output, at approximately 3 efficiency, for 500 hours of operation. Liquid coolants for use with the pump lamp were to be recommended. The optimal geometry of the lamp envelope for maximizing efficiency was investigated by using a standard state of the art krypton arc lamp with a quartz envelope, tungsten rod seals and an externally water cooled anode. A 6 mm bore by 2 inch 50.8mm arc length lamp, filled to 8 atmospheres, operated in an elliptical laser cavity, gave the desired 100 watts laser output at 3.3 efficiency. The approach to preventing degradation of lamp efficiency was to decrease wall deposits arising from its electrodes and to utilize high temperature lamp processing. To this end, three types of quartz envelope lamps having internal water cooled anodes were designed and tested. The type with tungsten tubing sealed into the lamp gave the desired 500 hour life, but the high efficiency obtained with the standard lamp was not obtained. Freon E-3 is the only presently known coolant that can meet the aircraft operational requirements of MIL-E-5400H. Water cooling and the installation of heaters in the recirculating pump system is more feasible at this time.