Neutron time-of-flight ion temperature diagnostic for inertial-confinement-fusion experiments

• Published in: Review of scientific instruments 1992-10, Vol.63:10
• Main Authors: Chrien, R.E., Simmons, D.F., Holmberg, D.L.
• Format: Article
• Language: English
• Subjects: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 700320 - Plasma Diagnostic Techniques & Instrumentation- (1992-); DESIGN; LASL; MEASURING INSTRUMENTS; NATIONAL ORGANIZATIONS; NEUTRON DETECTORS; NOVA FACILITY; PHOTOMULTIPLIERS; PHOTOTUBES; PLASMA DIAGNOSTICS; RADIATION DETECTORS; RESOLUTION; SCINTILLATION COUNTERS; SCINTILLATOR-PHOTODIODE DETECTORS; TIME-OF-FLIGHT METHOD; US AEC; US DOE; US ERDA; US ORGANIZATIONS
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.1143540

We are constructing a {ital T}{sub {ital i}} diagnostic for low neutron yield (5{times}10{sup 7} to above 10{sup 9}) {ital d}-{ital d} and {ital d}-{ital t} targets in the Nova facility at Livermore. The diagnostic measures the neutron energy spread with 960 scintillator-photomultiplier detectors located 28 m from the target and operates in the single-hit mode. Each detector can measure a single neutron arrival with time resolution of 1 ns or better. The arrival time distribution is constructed from the results of typically 200--500 detector measurements. The ion temperature is determined from the spread in neutron energy {Delta}{ital E}{sub {ital n}}{proportional to}{ital T}{sub {ital i}}{sup 1/2}, which is related to the arrival time spread by {Delta}{ital t}/{ital t}{congruent}{minus}(1/2){Delta}{ital E}{sub {ital n}}/{ital E}{sub {ital n}}. Each neutron arrival is detected by using a photomultiplier tube to observe the recoil proton from elastic scattering in a fast plastic scintillator. The timing electronics for each channel consist of a novel constant fraction-like discriminator and a multiple hit time-to-digital converter. The overall system design, together with single-channel performance data, is presented.