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.