Fast neutrons available through beam-target reactions driven by TW lasers

Abstract

Laser accelerated deuterons with energy ranging from 0.1 to 2 MeV were exploited as drivers of the $⁷$Li(d,n)$⁸$Be nuclear fusion reaction. Deuterons were emitted by CD$2$ plasma produced with focused laser intensity of ~ 3x10$¹⁶$ W/cm$²$. Deuterons accelerated upstream the laser beam impinged on a LiF catcher target producing there D-Li neutrons with energy > 13 MeV. Time-resolved signals of scintillation detectors were analysed with respect to the arrival time of fast neutrons at five scintillation detectors positioned around the target chamber. This analysis made it possible to determine energy of both the fusing deuterons and fusion neutrons. The energy spectrum of deuterons was also determined from the time-resolved charge density of ions derived from ion collector signals. Besides the neutrons produced through the 7Li(d,n)8Be fusion reaction, neutrons produced via the $²$H(d,n)$³$He reactions driven by the laser - CD$2$-plasma interaction were observed. The total dose of neutrons was determined employing high-sensitive bubble detectors (BD-PND). Since only a small fraction of generated fast deuterons were hitting the LiF catcher target, the maximum yield of neutrons from both the primary and secondary targets was ~ 3.5x10$⁸$ neutrons/shot, which gives a normalized yield of about 5.8x10$⁵$ neutrons/J. This value should still grow up when increasing the area of the catcher LiF target.