Clean Construction Protocol for the National Ignition Facility Beampath and Utilities

When the stadium-size, National Ignition Facility (NIF) is fully operational at the Lawrence Livermore National Laboratory (LLNL), its 192 laser beams will deliver 1.8 megajoules (500 terawatts) of energy onto a target to create extremely high temperatures and pressures for inertial confinement fusion research. Due to the high-energy-physics requirements of the NIF optical components, the optics and their surrounding beampath as well as the supporting utility systems must be fabricated, cleaned, assembled, and commissioned for precision cleanliness. This paper will provide an overview of the NIF cleanliness requirements, the clean construction protocol (CCP) specifications for the beampath and clean utilities, and techniques for verifying the CCP specifications. The NIF cleanliness requirements define limits for molecular and particulate contamination; the goal of these limits is to prevent contamination of the optical components. To prevent laser-induced damage and poor laser quality in the optical components, requirements for cleaning, assembly, installation, and commissioning in terms of particle and nonvolatile residue (NVR) levels are defined. The requirements in the interior of the beampath are parts-per-billion airborne molecular contamination (AMC) and Class 1 particulate levels. To achieve the cleanliness requirements for the beampath interior, a graded CCP approach is used as the NIF beampath andmore » utilities are being constructed by a partnership between LLNL and the construction contractor, Jacobs Facilities, Inc. in a stadium-size Class 100,000 building. Installation of the beampath components utilizes localized mini-environments of Class 100 or better, with budgets of cleanliness exposure or ''class-hours'' for each clean connection. Garment, equipment, and operational considerations are evaluated with process verification. Verification of the beampath and utility cleanliness is performed with cleanliness exposure monitoring, evaluating particulates with ''swipes'' and the LLNL-developed Precision Cleanliness Verification System (PCVS), and measuring NVRs and AMCs with analytical chemistry techniques. Preliminary cleanliness verification indicates that the CCP specifications are achieving the NIF cleanliness requirements for the beampath and clean utilities.« less