Next Generation Gamma-ray Cherenkov Detectors for ICF

Fusion reaction history and ablator areal density measurements for Inertial Confinement Fusion experiments at the National Ignition Facility are conducted using the Gamma Reaction History diagnostic (GRH-6m). Future Gas Cherenkov Detectors (GCD) will ultimately provide ~200x more sensitivity, reduce the effective temporal resolution from ~100 to ~10 ps and lower the energy threshold from 2.9 to 1.8 MeV, relative to GRH-6m. The first phase consisted of inserting the existing coaxial GCD-3 detector into a reentrant well which put it within 4 meters of the implosion. This diagnostic platform has allowed assessment of the x-ray radiation background environment within the well which will be fed into the shielding design for a follow-on “Super” GCD. It has also enabled use of a revolutionary new pulse-dilation photomultiplier tube (PD-PMT) to improve the effective measurement bandwidth by >10x relative to current PMT technology. The next phase is to improve sensitivity by increasing solid angle. This can be accomplished with a single GCD w/ PD-PMT on a TANDM diagnostic insertor, or multiple smaller GCDs on a TANDM with standard PMTs. The PD-PMT version would provide unprecedented temporal resolution, while the multiple GCD concept would allow for time-resolved mix measurements.