The National Ignition Facility (NIF) Opacity Spectrometer (OpSpec) is a modular spectrometer designed initially for opacity experiments on NIF. The design of the OpSpec is presented in light of the requirements and constraints. Potential dispersing elements and detector configurations are presented, and the advantages and disadvantages of each configuration are discussed. The full OpSpec design covers the energy range from approximately 550 eV to 2 keV. The energy resolution of the OpSpec is E/ΔE > 500. Applications of the OpSpec are discussed, including relevant astrophysical applications for NIF experiments, and will compliment recently published work on the Z machine. (Bailey, et al., Nature 517, 56-59 (2015).) This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy.
The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory uses the world’s largest and most
energetic laser system to explore Inertial Confinement Fusion (ICF) and High-Energy-Density (HED) physics, with the
potential of creating pressure and density conditions normally found in the cores of stars or large planets. During NIF
experiments, the laser energy is directed to the target, driving the desired physics conditions, and the breakup of the
target. During this breakup there is the potential to generate debris fields with both vaporized and solid target material,
traveling at extremely high velocities (~10 km/s). For future shots, it is desirable to minimize distribution of the certain
target materials within NIF. The High Energy Imaging Diagnostic (HEIDI), which comes within 8 cm of the target, will
be modified to minimize the distribution of the ejected material. An external cone will be added to HEIDI which will
block a larger angle than the existing hardware. Internal shielding will be added to isolate target material within the front
portion of the diagnostic. A thin aluminum bumper will slow low-density vaporized material and contribute to the
breakup of high velocity particles, while a thicker wall will block solid chunks. After the shot, an external cover will be
installed, to contain any stray material that might be disturbed by regular operations. The target material will be retrieved
from the various shielding mechanisms and assayed.
This paper describes the design considerations for Target Diffraction In-Situ (TARDIS), an x-ray diffraction diagnostic
at the National Ignition Facility. A crystal sample is ramp-compressed to peak pressures between 10 and 30 Mbar and,
during a pressure hold period, is probed with quasi-monochromatic x-rays emanating from a backlighter source foil. The
crystal spectrography diffraction lines are recorded onto image plates. The crystal sample, filter, and image plates are
packaged into one assembly, allowing for accurate and repeatable target to image plate registration. Unconverted laser
light impinges upon the device, generating debris, the effects of which have been mitigated. Dimpled blast shields, high
strength steel alloy, and high-z tungsten are used to shield and protect the image plates. A tapered opening was designed
to provide adequate thickness of shielding materials without blocking the drive beams or x-ray source from reaching the
crystal target. The high strength steel unit serves as a mount for the crystal target and x-ray source foil. A tungsten body
contains the imaging components. Inside this sub-assembly, there are three image plates: a 160 degree field of view
curved plate directly opposite the target opening and two flat plates for the top and bottom. A polycarbonate frame,
coated with the appropriate filter material and embedded with registration features for image plate location, is inserted
into the diagnostic body. The target assembly is metrologized and then the diagnostic assembly is attached.
This paper describes the development and performance of a sensor system that was utilized for autonomous navigation of an unmanned ground vehicle. Four different sensor types were integrated to identify obstacles in the vicinity of the vehicle and to identify smooth terrain that could be traversed at speeds up to thirty miles per hour. The paper also describes a sensor fusion approach that was developed whereby the output of all sensors was in a common grid based format. The environment around the vehicle was modeled by a 120×120 grid where each grid cell was 0.5m× 0.5m in size and where the orientation of the grid lines was always maintained parallel to the north-south and east-west lines. Every sensor output an estimate of the traversability of each grid cell. For the three dimensional obstacle avoidance sensors (rotating ladar and stereo vision) the three dimensional point data was projected onto the grid plane. The terrain traversability sensors, i.e. fixed ladar and monocular vision, estimated traversability based on smoothness of the spatial plane fitted to the range data or the commonality in appearance of pixels in the grid cell to those directly in front of the vehicle, respectively.