NEUTRON-STREAK-CAMERA AND FRAMING-CAMERA DIAGNOSTICS FOR ICF IMPLOSIONS

Detailed measurements of the time dependence of the neutron flux from the implosion of DT- and/or DD-filled targets are required to better our understanding of inertial confinement fusion (ICF). Past efforts at developing fast neutron detectors have generally suffered from a lack of sensitivity and/or insufficient time resolution. In this paper we report on a new streak-camera diagnostic for directly time-resolving the neutron burnwidth for ICF implosions. The technique uses elastic scattering of the neutrons in CH2 to convert the neutron signal to a recoil-proton signal, which is proximity coupled to a CsI secondary-electron emitter. The proton-generated, low-energy, secondary electron emission is subsequently recorded with a standard X-ray streak camera. An X-ray signal is recorded on the streak camera simultaneously with the neutron-produced signal and provides an accurate timing fiducial for burn-time measurements. We have recorded usable signals from the implosion of DT-fiIled targets producing yields of 3 X 10(10) neutrons, with a target to photocathode distance of 30 cm. The calculated time resolution is better than 20 ps for the 14.1-MeV DT neutrons and 10 ps for the 2.45-MeV DD neutrons. Our technique for recording the neutron flux can also be extended to high-speed framing cameras, currently capable of 35-ps-duration gate times. The framing cameras may be used to record the burnwidth and/or the neutron energy spectrum. Also, time-resolved neutron imaging of the core should be possible for neutron yields > 10(12).