Forward-looking insights in laser-generated ultra-intense γ-ray and neutron sources for nuclear application and science

Abstract

Ultra-intense MeV photon and neutron beams are indispensable tools in many research fields such as nuclear, atomic and material science as well as in medical and biophysical applications. For applications in laboratory nuclear astrophysics, neutron fluxes in excess of 1021 n/(cm2 s) are required. Such ultra-high fluxes are unattainable with existing conventional reactor- and accelerator-based facilities. Currently discussed concepts for generating high-flux neutron beams are based on ultra-high power multi-petawatt lasers operating around 1023 W/cm2 intensities. Here, we present an efficient concept for generating γ and neutron beams based on enhanced production of direct laser-accelerated electrons in relativistic laser interactions with a long-scale near critical density plasma at 1019 W/cm2 intensity. Experimental insights in the laser-driven generation of ultra-intense, well-directed multi-MeV beams of photons more than 1012 ph/sr and an ultra-high intense neutron source with greater than 6 × 1010 neutrons per shot are presented. More than 1.4% laser-to-gamma conversion efficiency above 10 MeV and 0.05% laser-to-neutron conversion efficiency were recorded, already at moderate relativistic laser intensities and ps pulse duration. This approach promises a strong boost of the diagnostic potential of existing kJ PW laser systems used for Inertial Confinement Fusion (ICF) research.

Non-destructive inspection of water or high-pressure hydrogen gas in metal pipes by the flash of neutrons and x rays generated by laser

“…17 The secondary target was a beryllium (Be) block (ϕ5 × 10 mm). When ions accelerated from the CD foil bombard the Be target, fast neutrons with energies of several MeV are generated via the 9 Be(d, n) 10 B and 9 Be(p, n) 9 B reactions. 29 The Be target was embedded in a circular truncated cone polyethylene (top diameter: 3.4 cm, bottom diameter: 7.4 cm, and height: 4 cm) with a density of 0.96 g/cm 3 to decelerate immediately fast neutrons to low energies.…”

“…6 Neutrons have already been applied in wide areas of research because of their charge neutrality and high transmittance to most substance. Laser-driven neutron sources (LDNSs) [6][7][8][9][10][11][12][13][14][15][16][17][18] are compact sources realized by high-power lasers. LDNSs based on laser-ion acceleration include two targets.…”

“…19 With moderators such as high density polyethylene located near the second target, the fast neutrons are decelerated to epithermal, 13 thermal, 14 and cold 15 regions to adapt for the study of various science and engineering applications. LDNSs have been studied [6][7][8][9][10][11][12][13][14][15][16][17][18] for their following features: (i) each neutron pulse has a short time duration (∼ns), (ii) neutrons could be generated from a compact space smaller than 1 cm 3 , and (iii) it is possible to produce different types of radiations including x rays 20 at the same laser shot. Because of the former two features, LDNSs could be used for neutron radiography with short time and high spatial resolution.…”

Creation and direct laser acceleration of positrons in a single stage

“…It is worth noting that current technology already allows to drive such beams with a charge of 10 pC, in particular with laser wakefield acceleration [61][62][63][64]. Higher electron beam charges of 100 nC are becoming available [67][68][69][70][71][72][73] and could be used to create and inject more positrons.…”

“…The main difficulty will be to achieve the spatio-temporal synchronization on the order of micrometers and femtoseconds. One way to address this challenge is to use relativistic electron beams of high charge (∼ 100 nC) and large size (∼ ps and ∼ 100 µm), produced via DLA with pico-second lasers [67][68][69][70][71][72][73]. For multi-laser facilities, these beams also offer the opportunity to increase the number of positrons created and accelerated in a plasma channel.…”