4 research outputs found
Recommended from our members
Preliminary report: NIF laser bundle review
As requested in the guidance memo {sup 1}, this committe determined whether there are compelling reasons to recommend a change from the NIF CDR baseline laser. The baseline bundle design based on a tradeoff between cost and technical risk, which is replicated four times to create the required 192 beams. The baseline amplifier design uses bottom loading 1{times}4 slab and flashlamp cassettes for amplifier maintenance and large vacuum enclosures (2.5m high {times} 7m wide in cross-section for each of the two spatial filters in each of the four bundles. The laser beams are arranged in two laser bays configured in a u-shape around the target area. The entire bundle review effort was performed in a very short time (six weeks) and with limited resources (15 personnel part-time). This should be compared to the effort that produced the CDR design (12 months, 50 to 100 personnel). This committee considered three alternate bundle configurations (2{times}2, 4{times}2, and 4{times}4 bundles), and evaluated each bundle against the baseline design using the seven requested issues in the guidance memo: Cost; schedule; performance risk; maintainability/operability; hardware failure cost exposure; activation; and design flexibility. The issues were reviewed to identify differences between each alternate bundle configuration and the baseline
Recommended from our members
NIF laser bundle review. Final report
We performed additional bundle review effort subsequent to the completion of the preliminary report and are revising our original recommendations. We now recommend that the NIF baseline laser bundle size be changed to the 4x2 bundle configuration. There are several 4x2 bundle configurations that could be constructed at a cost similar to that of the baseline 4x12 (from 11M less than the baseline; unescalated, no contingency) and provide significant system improvements. We recommend that the building cost estimates (particularly for the in-line building options) be verified by an architect/engineer (A/E) firm knowledgeable about building design. If our cost estimates of the in-line building are accurate and therefore result in a change from the baseline U-shaped building layout, the acceptability of the in-line configuration must be reviewed from an operations viewpoint. We recommend that installation, operation, and maintenance of all laser components be reviewed to better determine the necessity of aisles, which add to the building cost significantly. The need for beam expansion must also be determined since it affects the type of bundle packing that can be used and increases the minimum laser bay width. The U-turn laser architecture (if proven viable) offers a reduction in building costs since this laser design is shorter than the baseline switched design and requires a shorter laser bay
Laser coupling to reduced-scale targets at NIF Early Light
Deposition of maximum laser energy into a small, high-Z enclosure in a short laser pulse creates a hot environment. Such targets
were recently included in an experimental campaign using the first four of
the 192 beams of the National Ignition Facility [J. A. Paisner, E. M.
Campbell, and W. J. Hogan, Fusion Technology 26, 755 (1994)], under
construction at the University of California Lawrence Livermore National
Laboratory. These targets demonstrate good laser coupling, reaching a
radiation temperature of 340 eV. In addition, the Raman backscatter spectrum
contains features consistent with Brillouin backscatter of Raman forward
scatter [A. B. Langdon and D. E. Hinkel, Physical Review Letters 89, 015003 (2002)]. Also,
NIF Early Light diagnostics indicate that 20% of the direct backscatter
from these reduced-scale targets is in the polarization orthogonal to that
of the incident light
X-ray flux and X-ray burnthrough experiments on reduced-scale targets at the NIF and OMEGA lasers
An experimental campaign to maximize radiation drive in small-scale
hohlraums has been carried out at the National Ignition Facility
(NIF) at the Lawerence Livermore National Laboratory (Livermore, CA,
USA) and at the OMEGA laser at the Laboratory for Laser Energetics
(Rochester, NY, USA). The small-scale hohlraums, laser energy, laser
pulse, and diagnostics were similar at both facilities but the
geometries were very different. The NIF experiments used on-axis
laser beams whereas the OMEGA experiments used 19 beams in three
beam cones. In the cases when the lasers coupled well and produced
similar radiation drive, images of x-ray burnthrough and laser
deposition indicate the pattern of plasma filling is very different