HTPD 2018

The next-generation Magnetic Recoil Spectrometer, called MRSt, will provide time-resolved measurements of the DT-neutron spectrum from Inertial Confinement Fusion (ICF) implosions at the National Ignition Facility (NIF). These measurements will provide critical information about the time evolution of the fuel assembly, hot-spot formation, and nuclear burn. The absolute neutron spectrum in the energy range of 12-16 MeV will be measured with high accuracy (~5%), unprecedented energy resolution (~100 keV) and, for the first time ever, time resolution (~20 ps). Crucial to the design of the system is a CD (or CH) conversion foil for the production of recoil deuterons (or protons) as close to the implosion as possible to provide a small source for the ion-optics of the MRSt magnet system. The foil-on-hohlraum technique has been demonstrated by placing a 1-mm-diameter, 40-μm-thick CD foil on the hohlraum diagnostic band along the line-of-sight of the current time-integrating MRS system, which measured the recoil deuterons. In addition to providing validation of the foil-on-hohlraum technique for the MRSt design, substantial improvement of the MRS energy resolution has been demonstrated.
This work was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.