Tertiary fusion neutron diagnostic for density-radius product and stability of inertial confinement fusion

The fluence of high-energy (>14 MeV) ''secondary'' neutrons, produced in D--T reactions involving suprathermal fuel ions created by elastic scattering with 14-MeV ''primary'' neutrons, yields information about the fuel density-radius product (rhoR) and the hydrodynamic stability of inertial-confinement fusion (ICF) targets. The suprathermal ions, produced in proportion to the fuel rhoR, create secondary neutrons with energies ≤30 MeV when fusing with a thermal ion. The ratio of secondary to primary neutrons determines the mean fuel rhoR. Since secondary neutrons, which are mainly formed near the fuel tamper interface with energies >24 MeV, are radially directed, the detection of their angular distribution provides a unique measurement of the deviation from spherical geometry of the fuel rhoR. Valid for fuel rhoR>0.1 g/cm2 and D--T yield above 1014, this diagnostic would be valuable in upcoming ICF experiments