As a part of TW Nd:glass laser system, two Nd:glass rod amplifiers were designed, fabricated and tested in this study. The rod amplifiers were seeded by a Q-switched cw modelocked Nd:YLF oscillator which generates a pulse train of 30 psec pulses in 10 nsec interval. Single pulse was selected from the pulse train using a Pockels cell made of $KD^*P$ crystal. The single pulse with maximum energy could be selected when the delay time between the trigger pulses of Q-switching and high voltage pulse applied to the Pockels cell was 3.2μsec. The shot-to-shot fluctuation of the peak intensity of the selected single pulse was less than 5%, and the contrast ratio was larger than 950. Two stage Nd:glass amplifers have rods of 360mm length and 16mm and 30mm diameter each. They are pumped by four Xe-flashlamps with quadruple elliptical reflector whose ellipsiticies were optimized by the ray tracing method for uniform and efficient pumping. A Xe-flashlamp with 100μF capacitor was discharged with the peak current of 3.3kA and the pulse duration of 250μsec at 5kV charging voltage. The maximum energy gain could be obtained when the delay time between trigger pulses for the flashlamp discharging and the single pulse selection was 480μsec in this experiment. The measured gains for various applied capacitor voltages were matched well with the theoretical gain values calculated with the squarepulse approximation, and the energy gains were 55 and 12 for the first and the second amplifiers, respectively. To clean up the inhomogeneous spatial beam profile caused by the diffraction effect and the nonuniform flashlamp pumping in the amplifier, a spatial filter and a vacuum spatial filter were designed and installed. Spatial intensity distribution was measured with a CCD camera and a image frame grabber, and it was shown that the beam quality was improved by image relaying and spatial filtering technique.
