Weare in the midst of constructing an amplifier laboratory (Amplab) that will be the physics and engineering proving ground for full sized segmented glass amplifiers ofdesigns that will outfit the National Ignition Facility (NIF) and Laser Megajoule (LMJ) projects. Amplab will demonstrate the cornerstone mechanical, electrical and optical concepts that support the NTF and LMJ amplifier schemes. Here we address the optical diagnostics that will be used to characterize optical performance ofthe amplifiers. We describe, the apparatus that will be used in pulsed measurements ofgain distribution and wave-front distortions. The large aperture diagnostic system or LADS, is now being built through a collaborative effort between CEL-V and LLNL. The LADS will provide measurements ofgain and wave front distortions over the full extracting aperture ofthe NIF and LMJ prototype amplifiers. The LADS will be able to address each of eight apertures via motorized stages and following semi-automated alignment, take data on the aperture ofinterest. The LADS should be operational in mid-'97 at LLNL and will be used to characterize the optical performance ofthe veiy first full scale prototype 4 x 2 NIF and LMJ amplifiers. It will be transported to Bordeaux, France to make similar measurements during activation ofthe first 8-aperture LMJ-like facility (LIL) that is planned to start in the near future. The gain measurement will map the gain distribution ofeach ofeight 40 by 40 cm apertures. Small signal gain of 5 %-per-cm is the nominal operating point (lamps fired at 20% of their explosion energy). It is desired to measure the small signal gain ofthe amplifier with a resolution ofO. 1% ( 0.005 %per-cm) at the center ofthe aperture, 0.5% at the corners, or better. The amplifier pump distribution is tailored in order to counteract the effects of amplified spontaneous emission that tends to deplete gain in areas near the edges. This diagnostic will be useful in amplifier optimization experiments. Subtle effects of shaping reflector surfaces, the tarnishing of silver or the damage to reflector coatings could be found correlated to the gain data and thus, will be readily monitored.

Date Published: 8 December 1997
PDF: 5 pages
Proc. SPIE 3047, Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference, (8 December 1997); doi: 10.1117/12.294270

Published in SPIE Proceedings Vol. 3047:
Solid State Lasers for Application to Inertial Confinement Fusion: Second Annual International Conference
Michel L. Andre, Editor(s)