NIF diagnostics described at American Chemical Society meeting

Breanna Bishop, LLNL, (925) 423-9802, bishop33@llnl.gov

During construction, the 10-meter diameter target chamber of the National Ignition Faciliity was assembled from 10-centimeter-thick aluminum panels. Holes in the chamber provide access for the laser beams and viewing ports for NIF diagnostics.

Laboratory researchers gave presentations about the National Ignition Facility's diagnostic equipment in a symposium organized by LLNL's Dawn Shaughnessy at the American Chemical Society's Meeting on Materials for Health and Medicine Aug. 19-23.

Carol Velsco and LLNL colleagues described the Radiochemical Analysis of Gaseous Samples (RAGS) apparatus for NIF nuclear diagnostics, which collects gases produced during ignition to determine NIF target capsule areal density and ablator-fuel mix. Elements added to the innermost layers of the capsule undergo nuclear activation and following a shot, the activated gases are pumped out of the target chamber and transported to the RAGS apparatus for analysis.

In a related presentation, "Solid Debris Collection for Radiochemical Diagnostics at NIF," Julie Gostic and LLNL colleagues discussed the role of solid debris collection in a variety of inertial confinement fusion experiments at NIF, including capsule diagnostics, stockpile stewardship and nuclear physics measurements.

In addition, Darren Bleuel and colleagues from LLNL, the University of New Mexico and Sandia National Laboratories described the extensive suite of neutron activation diagnostics used to measure neutron yields at NIF. Neutron yields are routinely measured with activation to an accuracy of 7 percent, the researchers said, and are in excellent agreement both with each other and with neutron time-of-flight and magnetic recoil spectrometer measurements.

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