(88e) Measurement of the 3He Permeability of Deuterium-Tritium-Filled Fused Silica Inertial Confinement Fusion (ICF) Targets to Study the Effects of 3He on Neutron Emission during Implosion

A set of laser implosion experiments were conducted at the OMEGA laser at the University of Rochester, Laboratory for Laser Energetics (LLE) to study the effect of ³He concentration in DT-filled target shells on fusion yield in ICF implosions. Eleven laser fusion shells consisting of 1100-µm diameter, hollow, fused silica spheres with 4.6 to 4.7-µm-thick walls were loaded with 520 kPa of deuterium-tritium (DT) and then with ³He (101.3 or 520 kPa). The ³He permeabilities of the shells were determined by measuring the pressure rate of rise into a system with known volume. A mathematical method was developed that relied on the experimental fill pressure and time, and the rate of rise data to solve differential equations using MathCAD to simultaneously calculate ³He permeability and initial ³He partial pressure inside the shell. Because of the high permeation rate for ³He out of the shells compared to that for DT gas, shells had to be kept under ³He until immediately before being laser imploded or ?shot? at LLE. The ³He partial pressure in each individual shell at shot time was calculated from the measured ³He permeability. Neutron and gamma yields from an implosion were shown to decrease with increasing ³He addition.