LLNL, Livermore, California, USA
The Advanced Radiographic Capability (ARC) currently under development for the National Ignition Facility (NIF) will provide short (1-50 picoseconds) ultra high power (>1 Petawatt) laser pulses used for a variety of diagnostic purposes on NIF ranging from a high energy x-ray pulse source for backlighter imaging to an experimental platform for fast-ignition. A single NIF Quad (4 beams) is being upgraded to support experimentally driven, autonomous operations using either ARC or existing NIF pulses. Using its own seed oscillator, ARC generates short, wide bandwidth pulses that propagate down the existing NIF beamlines for amplification before being redirected through large aperture gratings that perform chirped pulse compression, generating a series of high-intensity pulses within the target chamber. This significant effort to integrate the ARC adds 40% additional control points to the existing NIF Quad and will be deployed in several phases over the coming year. This talk discusses some new unique ARC software controls used for short pulse operation on NIF and integration techniques being used to expedite deployment of this new diagnostic.
LLNL, Livermore, California, USA
The Advanced Radiographic Capability (ARC) at the National Ignition Facility was developed to produce a sequence of short laser pulses that are used to backlight an imploding fuel capsule. This backlighting capability will enable the creation of a sequence of radiographs during capsule implosion and provide an unprecedented view into the dynamics of the implosion. A critical element of the ARC is the diagnostic instrumentation used to assess the quality of the pulses. Pulses are steered to the diagnostic package through a complex optical path that requires precision alignment. A central component of the alignment system is the image analysis algorithms, which are used to extract information from alignment imagery and provide feedback for the optical alignment control loops. Alignment imagery consists of complex patterns of light resulting from the diffraction of pilot beams around cross-hairs and other fiducials placed in the optical path. This paper describes the alignment imagery, and the image analysis algorithms used to extract the information needed for proper operation of the ARC automated alignment loops.
LLNL, Livermore, California, USA
For many experiments planned on the National Ignition Facility (NIF), high-energy x-ray backlighters are an important diagnostic. NIF will be deploying this year a new Advanced Radiographic Capability (ARC) for generating these high-energy short-pulses. The precision of the Automatic Alignment (AA) for ARC is an important element in the success of the enhancement. A key aspect of the ARC AA is integration of the new alignment capabilities without disturbing the existing AA operations of NIF. Small pointing tolerances of 5 micron precision to a 10 micron target are required. After main amplification the beams are shortened by up to 1,000x in time in the ARC compressor vessel and aimed at backlighter targets in the NIF target chamber. Alignment Stability and Verification of the compressor gratings is critical to ensuring the ARC pulses meet their experimental specifications.