Performance Of The Beamlet Laser A Testbed For The National Ignition Facility PDF Download

The compact multi-pass laser design and the extensive use of optical component assemblies as line replaceable units (LRU) are essential to achieve the cost efficiency of the National Ignition Facility design. These design philosophies require a new approach to start-up operation of the NIF 192-beam-line high-energy laser compared to existing fusion laser facilities. The limited access to the beam-line optics and the limited on-line verification and maintenance capability require that extensive component verification and alignment take place in off-line facilities before the LRUÕs are installed in the laser structure. We are developing a detailed plan for the start-up of the NIF facility. This plan includes systematic off-line component and LRU verification tests, LRU installation and prealignment, and sub-system acceptance tests, followed by a well defined set of operational test procedures to verify integrated performance. During integrated performance testing laser performance parameters of individual beam lines will be verified using a precision diagnostic system located in the NIF switchyard. If additional on-line calibration or performance testing is required, the LRU based architecture can accommodate the insertion of specialized in-line diagnostic LRUs at locations that require such additional testing during start-up. Multiple beam focal spot characteristics on disk targets in the NIF target chamber will be examined using X-ray diagnostics. We will discuss the detailed plan for the startup of the first bundle of 8 beam lines, a laser system by itself similar in size and complexity to the LLNL Nova laser, The discussion will include the application of lessons learned from start-up and operation of the Beamlet prototype beam line during the last 4 years. Experience on the first bundle of beams is essential to optimize the start-up procedures to expeditiously deliver the 23 remaining laser bundles to the operations program at the rate of one bundle per month to complete the NIF facility. The plan that we describe supports a gradual transition from the present ICF program based upon the 10-beam Nova laser system to an ICF program based upon the 192-beam-line National Ignition Facility, with all 24 bundles being available for operation in FY04. This plan includes a schedule for a phased bundle-by-bundle completion of integrated operational test procedures and hand over of laser bundles to the program for experimental operations. The early start-up of one bundle provides early experimental capability two years before completion of the NIF Project, and experience that will be essential to complete this transition plan on schedule in a cost effective way.