Micro-size picosecond-duration fast neutron source driven by a laser–plasma wakefield electron accelerator

Abstract

Pulsed fast neutron source is critical for the applications of fast neutron resonance radiography and fast neutron absorption spectroscopy. However, due to large transversal source-size (∼ mm) and long pulse duration (∼ ns) of traditional pulsed fast neutron sources, it is difficult to realize high contrast neutron imaging with high spatial resolution, and fine absorption spectrum. Here, we experimentally present a micro-size ultra-short pulsed neutron source by a table-top laser plasma wakefield electron accelerator driving photofission reaction in a thin metal converter. A fast neutron source with sourcesize of ∼500 µm and duration of ∼36 ps has been driven by a tens of MeV, collimated, micro-size electron beam via a hundred TW laser facility. This micro-size ultra-short pulsed neutron source has the potential to improve the energy resolution of fast neutron absorption spectrum dozens of times to e.g. ∼100 eV at 1.65 MeV, which could benefit for high quality fast neutron imaging and deep understanding theoretical model of neutron physics.

Laser Plasma‐Accelerated Ultra‐Intense Electron Beam for Efficiently Exciting Nuclear Isomers

“…We have also fired 70 consecutive shots at a repetition rate of 0.025 Hz under this parameter condition, the results were shown in ref. [39]. The average divergence angles in the x and y directions were $$7.$…”

“…We have also fired 70 consecutive shots at a repetition rate of 0.025 Hz under this parameter condition, the results were shown in ref. [39]. The average divergence angles in the x and y directions were 7.0 • ± 1.2 • and 6.1 • ± 1.3 • respectively, and the average charge was 15.59 ± 1.68 nC, in where the error represented the standard deviation.…”

“…When moving in the magnet, the electron beam angular distribution was recorded by a 20 cm × 20 cm SR‐type image plate (IP), which was covered with 200 $$\umu $$m copper to block low‐energy electrons. The electron beam charge was also calculated according to this IP, [ 39 ] which was scanned by a Typhoon‐7000 IP reader. The electron beam energy distribution was recorded by another SR‐type IP.…”

Prospect of ultrahigh-resolution fast neutron absorption spectroscopy based on a laser plasma electron accelerator

“…In the simulation, the neutron beam with the energy spectrum of Figure 5(c) passes through the sample; then one transmitted neutron is randomly selected via MATLAB code to be recorded and the recorded energy has corresponding uncertainty, which is shown in Ref. [12] (Figure 5(b)); finally, we repeat the selection process to accumulate enough transmitted neutrons to acquire a fine absorption spectrum, whose energy resolution is determined by the calculated result in Ref. [12]; the repetitive process is the same to accumulate laser shots.…”

“…LWFAs have achieved many successes in recent years, including record beam energy of up to 8 GeV in cm length [19] , beam duration down to femtoseconds (fs), driven X-ray free-electron lasers [20][21][22] , etc. Moreover, the LWFA fs duration electron beam can drive ultra-fast Bremsstrahlung γ-ray photons in a thin metal target, and further induce photo-nuclear reactions to realize a tens of picoseconds (ps) pulse duration fast neutron source, which has great potential to improve the energy resolution of FNAS [6] two orders of magnitude higher than traditional fast neutron sources [11,12] . However, in experiments, it is difficult for the laserdriven ps duration pulsed fast neutron source to realize a fine absorption spectrum in a single shot, due to the low yield [23][24][25][26] and, in particular, the slow temporal response of the neutron time-of-flight (nTOF) detector [27] .…”