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

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Abstract
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 (ρR) and the hydrodynamic stability of inertial‐confinement fusion (ICF) targets. The suprathermal ions, produced in proportion to the fuel ρR, create secondary neutrons with energies ≤30 MeV when fusing with a thermal ion. The ratio of secondary to primary neutrons determines the mean fuel ρR. 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 ρR. Valid for fuel ρR>0.1 g/cm2 and D–T yield above 1014, this diagnostic would be valuable in upcoming ICF experiments.