NIF Spring Maintenance Period Successfully Completed
The spring NIF Facility Maintenance and Reconfiguration (FM&R) Period was successfully completed on April 28 as scheduled; 269 of 270 planned activities were completed and one minor task was deferred, for an overall 99.6 percent performance. “Great job, Team NIF!” commented NIF Operations Manager Bruno van Wonterghem. Among the completed tasks during the FM&R were:
Target Area Operations’ Mike Vacca installs new near-backscatter imager scatter plates inside the NIF Target Chamber. The task was completed on April 5.
Jeremy Huckins, JB McLeod, and Ed Howe monitor the successful insertion of AM6 transport mirrors in the 11-foot-high Advanced Radiological Capability (ARC) Parabola Vessel. The Parabola Vessel will focus ARC’s quadrillion-watt beams on a backlighter target near Target Chamber center to produce an x-ray “movie” to diagnose NIF target implosions with tens-of-picoseconds resolution.
(Left) in the Optics Assembly Building (OAB) Senior Technician Mike Dailey, along with Responsible Engineer Henry Hui and technician Alfonso Caballero, examine an AM7 parabolic mirror after mounting in a line replaceable unit (LRU) assembly for installation in the ARC Parabola Vessel. The AM7s are parabolic-faced with a focal length of about eight meters for focusing the ARC beams to a backlighter target in the Target Chamber. After focusing, the beam will reflect off a transport mirror and enter the target chamber. (Right) Hui, Dailey, and Mechanical Engineer Dain Holdener remove an AM7 LRU from the OAB wavefront verification system after completion of its metrology.
- Installation of parabola and transport mirrors in the Advanced Radiographic Capability (ARC) Parabola Vessel
- Advanced Tracking Laser Alignment System (ATLAS) first wall removal and re-installation; ATLAS will align all of the systems inside the Target Chamber using a single laser tracker
- Rewiring and testing of the Target Positioner (TARPOS) cables and positioning the Ignition Target Inserter and Cryostat (ITIC) for reinstallation on the TARPOS
- Installation and laser conditioning of more than 40 frequency-tripler crystals in NIF final optics assemblies; the crystals convert the infrared light from the NIF beamlines and the green light from the doubler (second harmonic) crystals to the third harmonic (ultraviolet) for delivery to Target Chamber center
- Re-installation of scatter plates used to evaluate backscattered light in conjunction with the near-backscatter imager (NBI) diagnostics
- Shot commissioning for alignment, ARC, Integrated Computer Control System, optics conditioning, and the Laser Performance Operations Model.
NIF Experiments Resume
On April 29-30, the first target shot since the FM&R, a shock-timing cryogenic “keyhole” target experiment, was conducted. All 192 NIF beams delivered 900 kilojoules of ultraviolet light to the target in a 375-terawatt peak power pulse. On April 30-May 1, a high-density carbon (HDC, or diamond) keyhole experiment was conducted. This HDC keyhole will be used to adjust the laser pulse for the second convergent ablator (ConA) re-emit experiment in the inertial confinement fusion high-foot (high initial laser pulse) campaign for future high-foot experiments.
Left) Target designer Nick Hash with a completed design of a 6.72-millimeter keyhole target; the cone and capsule are on the right. (Right) Target technician Jean Jensen installs the cone shield on a nearly completed keyhole target in the Bldg. 381 target fabrication facility.
Successful Tests of the NIF X-ray Spectrometer
The joint LLNL-Laboratory for Laser Energetics (LLE) team designing the NIF x-ray spectrometer (NXS) fielded three of the NXS instruments during a full day of experiments at the OMEGA Laser at the University of Rochester on April 4.
The NXS, which is sponsored by the Defense Threat Reduction Agency (DTRA), will bring time-resolved, high-spectral-resolution x-ray spectroscopy capability to NIF, and will be available to all users as a core facility diagnostic. The NXS continues the partnership between the Department of Defense’s DTRA and NIF in developing test capability and facility diagnostic capability.
The purpose of the first OMEGA tests was to obtain information on the instruments’ performance and deliver an absolute photometric calibration of the NXS before its first deployment at NIF, scheduled for June. Excellent data were measured for five of the 10 possible energy ranges selectable for the NXS.
The success of the first calibration shots is due to the excellent mechanical design of the NXS, engineered by Mark Bedzyk of LLE. The OMEGA shot operations crew provided superb support for the shots, supporting five lines of sight with remarkably efficient turnaround times. Chuck Sorce and Ray Bahr of LLE and Nick Whiting of LLNL orchestrated the complex NXS configuration changes efficiently and flawlessly. The day ended with 12 high-quality OMEGA shots.
The NXS team—Sean Regan of LLE and Kevin Fournier, Fred Perez, Maria Barrios, Shannon Ayers, Hui Chen, and Elijah Kemp of LLNL—expressed appreciation for the extra resources LLE dedicated to the day of shots.
The NIF x-ray spectrometer (NXS) will be installed on NIF. (Credit: Eugene Kowaluk, LLE)