S-AD-M-005
Chapter 1: System Overview
January 2006—Page 13 of 35
Table 1.2: Specifications for the 1053-nm chirped-pulse-amplification beams. Note
that the beams can be used for backlighting at all pulse widths from the
minimum shown up to 100 ps. When Beam 2 is not copropagating with
Beam 1, it has the same parameters as Beam 1.
Beam 1
Beam 2
Baseline performance
Maximum
intensity
Fast-ignitor
beam
Channeling beam
copropagated
Pulse width (ps)
1
10
100
Focal spot radius (
n
m)
10
10
20
Energy on target (kJ)
0.8
2.6
2.6
Intensity (W/cm
2
)
~2
#
10
20
~6
#
10
19
~3
#
10
18(a)
(a)
Limited by
B
-integral in beam combiner.
stretched pulse length of 1.13 ns, is capable of producing >4.0 kJ of energy at the input to the compressor.
The final grating (G4) is critical as it sees the fully compressed pulse and will damage first.
1.3.2 Long-Pulse Performance
Anticipated performance parameters of the four long-pulse beams are given in Table 1.3. The
UV on-target energies are derived from a conservative scenario in which the IR energy at each pulse
width is limited to 80% of the NIF design value. To allow for possible inhomogeneities in the frequency-
conversion crystals or alignment errors, the frequency-conversion efficiency is de-rated by 10% from
the calculated value, and the transport from the frequency-conversion crystals to the target (including a
4% diagnostic pickoff) is conservatively assumed to be 85%. The calculations used for Table 1.3 assume
low-risk, existing technologies and demonstrated UV damage fluences for optical coatings. In spite
of the de-rating of OMEGA EP energies relative to NIF design values, the OMEGA EP performance
requirement of 5 kJ/beam is met.
The performance of the laser chain for 1- and 10-ns square pulses is limited by the peak fluences
and damage limits of the optical components in the OMEGA EP beamline after the last pass through
the cavity, the booster-amplifier section, and the UV transport to target. The most damage-threatened
components in the UV subsystem in both the 1-ns and 10-ns cases are the UV transport mirrors.
Careful image relaying to the plane of the first UV transport mirror is necessary to ensure optimal
system performance. The next most threatened UV component is the output surface of the FCC’s. In
the IR sections, the cavity polarizer in reflection is the most damage-threatened component. The limit
at 10 ns corresponds to the maximum pulse width that can be produced by the current front-end sources
design.
Table 1.3 also lists the UV energy potential of the system, assuming a modest increase in the
current coating damage fluence. The long-pulse performance of OMEGA EP for pulses ≤1 ns is limited
by the accumulated
B
-integral in the UV subsystem (which is held to ≤2). For pulse lengths longer than
~1 ns, the performance is limited by the damage fluence of current UV high-reflector coatings. This
scales with Gaussian pulse width
x
as 5.2
x
1/3
J/cm
2
, with
x
measured in nanoseconds.
Summary of Contents for Volume VII-System Description
Page 38: ......
