S-AD-M-005
Chapter 1: System Overview
January 2006—Page 2 of 35
1.
Laser Diagnostics
1..1 Infrared Diagnostic Package (IRDP)
A suite of diagnostic instrumentation is dedicated to each of the beamlines. These diagnostic
packages are designed to provide comprehensive information about system performance in preparation
for and during a target shot. Measurements are made of the beam energy, pulse shape, near-field and
far-field spot profiles, and full-aperture beam wavefront. Alignment diagnostics point and center the
beam and are used to monitor alignment from the injection point to the amplified beam emerging from
the end of the TSF. The IRDP tables are located between the two spatial-filter pinhole vessels.
The source beam for the IRDP comes from the first surface reflection of the IR diagnostic beam
splitter (IR-DBS). This beam may originate from a cw laser on the infrared alignment table (IRAT) or
from the Laser Sources Bay (5-Hz pulse). These beams are injected onto the injection mirror located
within the TSF from the injection table. The IR-DBS is a flat, wedged plate oriented at 0.1º relative to
beam normal and is located at the output end of the TSF. Approximately 0.2% of the incident light is
reflected from the front surface of the IR-DBS back through the TSF output lens where the converging
beam is folded to fit within the TSF pinhole area vacuum vessel. There the beam is collimated and
delivered to the IRDP optics table where it acts as the source beam for the various alignment and shot
diagnostics.
1..2 Short-Pulse Diagnostics Package (SPDP)
Each of the two short-pulse beams has a dedicated diagnostics suite comprised of at least ten
individual diagnostic instruments. These instruments diagnose the properties of the beams before they
are co-aligned and exit the GCC. The SPDP provides information on beam quality, energy, alignment,
spectrum, optical component damage, output wavefront, pulse width, and pulse contrast.
After each short pulse beam is temporally compressed by the pulse compressors and wavefront
corrected by the deformable mirror, they are directed to a “leaky” mirror where the majority of light
incident on the mirror reflects off the surface but a small portion bleeds through the mirror, forming the
diagnostic beam. For the upper beam, a flat mirror folds the transmitted light through the “leaky” mirror
into an optic with a slight wedge. The first surface of the wedge is uncoated, providing a 4% reflection,
while the rear surface of the wedge is highly reflective. The small pointing difference between the beam
reflecting off the front and rear surfaces of the wedge allows an operator to select either the low- or
high-transmission path. In the case of the lower compressor beam, a single 45º fold mirror replaces the
wedge and fold mirror pair. In either the upper or the lower compressor, the diagnostic beam is then
directed to the first of a pair of down-collimation lenses. The use of a wedge having two reflectances
reduces
B
-integral for on-shot measurements and optimizes energetics for the diagnostic instruments in
pre-shot mode where only alignment laser beams are available.
The SPDP also includes a dual-wavelength IR alignment laser (1053 nm and 1047 nm) that can be
used to illuminate the compressor short-pulse transport path to the target, and the Fizeau interferometer in
the GCC. This beam allows alignment and setup of the pulse compressors to be conducted independently
of the main beamline.
Summary of Contents for Volume VII-System Description
Page 38: ......
