NIF moves closer to early light
The National Ignition Facility’s 192 laser beams are organized into 24 groups of 8-laser beams called bundles. Each bundle contains 130 line replaceable units (LRUs), which hold the functional optical elements for each laser beamline.
Last week, the 100th LRU was installed in Bundle 31, the bundle targeted
for initial laser activation and testing. This installation is a significant
step toward NIF early light laser activation and exemplifies the successful
integration of the NIF being carried out by multidisciplinary laboratory
and contractor teams.
When assembled, NIF LRUs are precision electro-optical/mechanical structures weighing between 500 and 1,000 kilograms. LRU components are received at the NIF warehouse on Patterson Pass Road. Optical components are shipped to the Optics Processing Laboratory in Bldg. 391 (home of the former NOVA laser) where they are inspected, cleaned and mounted before they are delivered to the Optics Assembly Building (OAB), adjacent to NIF. There, LRU design and OAB teams assemble and test the LRUs in a class 100 cleanroom environment. These tests validate the cleanliness, alignment, and operation of these complex assemblies.
Teams from Systems Engineering help to verify that the test data meets or exceeds LRU requirements before beampath installation.
"We rely on Systems Engineering ‘Expert Teams’ to help verify our results and make sure no facet is overlooked," said Gina Bonanno, associate project manager for assembly, installation, and refurbishment. "When we release an LRU, we’re certain that the optics are precisely aligned with the optical axis of the beamline, that the mounting process has not introduced distortions or contamination, and that the LRU will perform as designed."
Next in line, transport and handling teams use automated guidance vehicles to position and install the LRUs into the laser beampath infrastructure system. Since its completion in October, the beampath has been maintained in its operational cleanliness conditions. The LRU delivery vehicles maintain stringent cleanliness levels during transport and installation operations.
When Bundle 31 LRU installations began in May there were still more than 100 crafts workers installing water, air, electrical, mechanical, vacuum, and cooling utilities throughout the laser bay. "To our great pleasure, everything has gone according to schedule. This is a testament to the coordination efforts of many Laboratory groups and contractors and the willingness of all the teams to work together to execute a difficult assignment," Commissioning Manager Bruno Van Wonterghem said.
LRU associate project managers Steve Johnson and Doug Larson also are proud of the integrated team efforts. "Installation of this many LRUs puts us in a position to begin firing the flashlamps, which further cleans the laser amplifiers and provides the first online tests of NIF systems," Johnson said.
"The teamwork needed to build, validate and install this large number of flashlamp LRUs paves the way for our power conditioning teams to test the flashlamps and moves us closer to running the laser," Larson said.
Toward 10-kJ laser light activation Full installation and activation of Bundle 31 LRUs are required to support a NIF milestone of 10 kJ (kilojoules) of laser energy. The first step—full-energy, flashlamp shots — has already started. Subsequent LRU installations will support alignment of laser bay optics, verify systems that correct for wavefront distortions and test overall controls, timing, and diagnostics. Installation of amplifier LRUs will enable low-energy laser shots, precursors to full-energy laser operation.
Another planned milestone of NIF early light entails attaining 4 kJ of ultraviolet laser light at the center of the target chamber next spring. The wavelength of this light will be converted from 1.053 µm (infrared) to 351 µm (near ultraviolet) through frequency conversion crystals inside a final optics assembly LRU mounted on the target chamber.
Initial experiments will accelerate and illuminate flat foil targets, which will generate shock waves that reveal equation-of-state data relative to stockpile stewardship and basic science. Some experiments will focus three laser beams onto a foil while the fourth beam illuminates a backlighter target that takes radiographs of the shock front, providing important material properties information that can only be provided by laser systems. Other experiments will measure hydrodynamic instabilities similar to those observed in supernovae.
"Livermore will have a world-class experimental laser facility with the activation of the first NIF quad," said Brian MacGowan, associate project manager for NIF mission support. The NIF laser will have long-duration laser pulse capability with precise pulseshaping, enabling unique experimental possibilities. "A single NIF quad is packaged in a small, solid angle, allowing for more efficient coupling to experiments. A NIF quad, although only 2 percent of the complete NIF laser, has the potential to provide more energy than that produced by all of the Nova laser."
The efforts of hundreds of additional NIF team members have enabled impressive construction, assembly, and testing progress. Included are the many support organizations from within the NIF project and throughout the Laboratory, vendors providing essential products and services according to demanding schedules and crafts people installing and integrating critical support utilities and systems. It is the continued support and dedication of all NIF team members that is making NIF a success.