Omega Volume VII-System Description, Руководство по эксплуатации

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Volume VII–System Description
OMEGA EP Operations Manual Page 12 of 35
The system is configurable so that Beamlines 1 and/or 2 may operate in short- or long-pulse
mode while Beamlines 3 and/or 4 operate in long-pulse mode since each beamline has its own seed
pulse. Beams 3 and 4 cannot be directed to the OMEGA target chamber.
1.3 System Performance Specifications
1.3.1 Short-Pulse Performance
The short-pulse beams are capable of compression to various pulse widths in the range of 1 to
100 ps. The top-level specifications for these beams are given in Table 1.2. Beam performance parameters
are given for (1) the maximum on-target intensity, (2) the 10-ps fast ignitor, and (3) the copropagated
channeling beam. For the baseline design, peak focused intensities of >10
19
W/cm
2
(using f /1.8 reflective
optics) are available at the shortest pulse width. For short-pulse backlighting, the pulse width chosen
will depend on the needs of the specific experiment.
The numbers quoted in Table 1.2 assume a system performance limited by the damage threshold
of the multilayer dielectric reflection gratings. The use of improved grating technology provides up to
~2.6 kJ of laser energy per beam. The pulse width of Beam 2, when copropagating with Beam 1, is limited
by the
B -integral accumulated while it passes through the beam combiner in the grating compressor
chamber, resulting in a maximum on-target intensity of ~4
#
10
18
W/cm
2
. For the normal operations,
the pulse width should be ~35 ps to obtain the minimum focal spot size, but a 20-ps pulse is possible for
experiments requiring a larger focal spot. The performance in short-pulse mode is strictly limited by the
damage fluence of the MLD compression gratings. The laser itself, even at the relatively short output-
G6861J1
Figure 1.4
Cutaway illustration of the OMEGA EP target chamber (TC) and the GCC (partial view) looking south. The TC selection
mirror (upper right) can be aligned to direct the temporally compressed beam to enter the backlighter port (blue) or sidelighter
port (red). A related geometry enables simultaneous backlighting and sidelighting within the OMEGA EP chamber. The
TC selection mirror may also be reoriented to direct the beam to the OMEGA TC (not shown).