Upgrades to the Radiochemistry Analysis of Gas Samples (RAGS) diagnostic at the National Ignition Facility

Abstract

ABSTRACT The Radiochemical Analysis of Gaseous Samples (RAGS) diagnostic apparatus operates at the National Ignition Facility (NIF). At the NIF, xenon is injected into the target chamber as a tracer, us ed as an analyte in the NIF targets, and generated as a fission product from 14 MeV neutron fission of depleted uranium contained in the NIF hohlraum. Following a NIF shot, the RAGS apparatus used to collect the gas from the NIF targ et chamber and then to cryogenically fractionate xenon gas. Radio-xenon and other activation products are collected and counted via gamma spectrometry, with the results used to determine critical physics parameters including: capsule areal density, fuel-ablator mix, and nuclear cross sections. We will discuss the following performance upgrades to the system: Modification of the xenon fractionator to allow collection of krypton. Krypton is an important target analyte and is also generated as fission gas in NIF shots. We have modified the cryostat to enable fractionation of xenon, krypton, or both. A translatable detector for quantification of the fission gases. An in situ Germanium detector is used to count the radio isotopes collected on the coldhead. NIF shots that incorporate depleted uranium in the hohlraum generate large amounts of fission gas, the radioactivity of which paralyzes the detector. We have designed a system that will adjust the detector-to-coldhead distance based upon either the count rate or the time after the NIF shot. Keywords: krypton, radiochemistry, cryogenic, nuclear diagnostic