Predicted neutron yield and radioactivity for laser-induced (p,n) reactions in LiF

Swift, D C ; McNaney, J M

关键词: ANNIHILATION;    DECAY;    DESIGN;    HALF-LIFE;    NEUTRON SOURCES;    NEUTRONS;    NUCLEI;    PHOTONS;    POSITRONS;    PRODUCTION;    PROTONS;    RADIOACTIVITY;   

DOI  :  10.2172/948208
RP-ID  :  LLNL-TR-410557
PID  :  OSTI ID: 948208
Others  :  TRN: US0901671

美国|英语

来源: SciTech Connect

【 摘 要 】

Design calculations are presented for a pulsed neutron source comprising polychromatic protons accelerated from a metal foil by a short-pulse laser, and a LiF converter in which (p,n) reactions occur. Although the proton pulse is directional, neutrons are predicted to be emitted relatively isotropically. The neutron spectrum was predicted to be similar to the proton spectrum, but with more neutrons of low energy in the opposite direction to the incident protons. The angular dependence of spectrum and intensity was predicted. The (p,n) reactions generate unstable nuclei which decay predominantly by positron emission to the original {sup 7}Li and {sup 19}F isotopes. For the initial planned experiments using a converter 1mm thick, we predict that 0.1% of the protons will undergo a (p,n) reaction, producing 10{sup 9} neutrons. Ignoring the unreacted protons, neutrons, and prompt gamma emission as excited nuclear states decay, residual positron radioactivity (and production of pairs of 511 keV annihilation photons) is initially 4.2MBq decaying with a half-life of 17.22 s for 6 mins ({sup 19}Ne decays), then 135Bq decaying with a half-life of 53.22 days ({sup 7}Be decays).