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The recent results on pulsed CO 2 laser, including the effects of preionization structure, electrode profile, and discharge circuit are reported. Two sizes of discharge gap, 70 mm and 100 mm were selected. For the 70 mm gap, lateral preionization was used; for the 100 mm gap, preionization beneath the meshed electrode, and mixed preionization beneath and beside the electrodes were all tested. Strong lateral discharge was found in the case of near-Rogowski profile or Stappaerts profile, and strong central discharge was found in the case of Ernst profile. When the near- Rogowski profiled electrode was paired with an Ernst profiled electrode, better performance was obtained. Discharge distribution corresponding to the spark pins under the mesh grid was found obviously, which means that the uniformity of preionization should be further improved. Small signal gain coefficient was measured to evaluate the discharge. For the experimental setup with 70 mm discharge gap and 4 liters discharge volume, the highest small signal gain coefficient was 2.94% cm -1 . When a laser cavity was installed, the highest pulsed energy obtained from this setup was 169 J. When the discharge volume was enlarged to 16 liters, pulsed laser energy up to 580 J was obtained.

As indicated by tests on several cameras, the dynamic range of the Lawrence Livermore Laboratory streak-camera system appears to be about two orders of magnitude greater than those reported for other systems for 10- to 200-ps pulses. The lack of a fine mesh grid in the RCA streak tube used in these cameras probably contributes to a lower system dynamic noise and therefore raises the dynamic range. A developmental tube with a mesh grid was tested and supports this conjecture. Order-of-magnitude variations in input slit width do not affect the spot size on the phosphor or the dynamic range of the RCA tube.