Volume VII–System Description
OMEGA EP Operations Manual
Page 30 of 35
1..3 Ultraviolet Diagnostic Package (UVDP)
The UVDP and alignment sensor package (ASP) tables are located on Levels 1 and 2 of the
target area structure (TAS) and are symmetrically arranged about the target chamber. These diagnostic
packages provide comprehensive information about system performance, both in preparation for and
during a target shot. Measurements are made of the beam energy, near-field (including IR) and far-field
spot profiles as well as contrast, and harmonic energies.
The source beam for the UVDP comes from the ultraviolet alignment table (UVAT) located on
the Laser Bay floor south of the TAS. A periscope mirror assembly (PMA), similar to OMEGA’s, directs
the alignment beam into the optical path prior to the FCC’s. A UV diagnostic beam splitter (UV-DBS)
provides 4% of the incident light to a transmissive off-axis parabola that relays 4% of the beam into the
UVDP and ASP. The remaining energy is blocked by a full-aperture calorimeter.
Because the high-energy pulsed beam is converted from IR to UV part way through the system,
the alignment system must include both IR and UV sources. A hand-off between the two alignment
sources takes place at the UV diagnostic package’s ASP. These utilize achromatic optics so that they
can function at both wavelengths and are located on the target area structure. Each beamline has its
own ASP that includes a special full-aperture pickoff optic that reflects 4% of the beam energy into the
diagnostic subsystem while allowing the remainder to propagate onward to the end mirror. During the
alignment process, a sample of the alignment beam is directed to the alignment sensor. On a shot, the
4% sample of the high-energy pulse is directed to beam performance diagnostics on the UVDP table.
The UV portion of the system is aligned using a 351-nm cw laser that is located on the UVAT
located on the Laser Bay floor, south of the TAS. The UVAT optics project a separate full-aperture
alignment beam into corresponding PMA’s. Each PMA functions to position movable mirrors to inject
the alignment beam into one beamline at a time.
Co-alignment of the IR and UV alignment beams in each beamline is achieved by steering the
PMA mirrors to point the UV alignment beam to the pointing reference in the UVDP-ASP. The portion
of the UV alignment beam that passes through the pickoff optic is then steered to the target by moving
the transport mirrors and confirmed to be aligned by retroreflection back to the UVAT.
1.. Full-Aperture Calorimetry
Full-aperture IR calorimeters are the primary diagnostics used to measure the absolute energy
of the IR long- and short-pulse beams, providing accurate energy measurements of the amplifier output
energies. Laser light incident on the calorimeter absorber glass (NG-11) is transferred to an aluminum
diffuser in the form of thermal energy that is converted to a voltage by a thermoelectric array. A data
acquisition and control system monitors the output voltage from the calorimeter.
Each of the four beamlines is equipped with an IR calorimeter that is located on the switchyard
tower and may be inserted into the beam path prior to a laser shot. The calorimeters in Beamlines 1 and
2 may be removed and re-installed on the short-pulse polarizer assembly (replacing the beam dump) to
measure the energy of the light reflected from the target.
Summary of Contents for Volume VII-System Description
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