The investigation of high intensity laser driven micro neutron sources for fusion materials research at high fluence

Abstract

The application of fast pulse, high intensity lasers to drive low cost DT point neutron sources for fusion materials testing at high flux/fluence is investigated. At present, high power bench-top lasers with intensities of 1018W/cm2 are routinely employed and systems capable of ⩾ 1021 W/cm2 are becoming available. These potentially offer sufficient energy density for efficient neutron production in DT targets with dimensions of around 100 μm. Two different target concepts are analysed - a hot ion, beam-target system and an exploding pusher target system - and neutron emission rates are evaluated as a function of laser and target conditions. Compared with conventional beam-target neutron sources with steady state liquid cooling, the driver energy here is removed by sacrificial vaporization of a small target spot. The resulting small source volumes offer the potential for a low cost, high flux source of 14 MeV neutrons at close coupled, micro (⩽ 1 mm) test specimens. In particular, it is shown that a laser driven target with ∼100 J/pulse at 100 Hz (i.e. ∼10 kW average power) and laser irradiances in the range Iλ2∼1017-1019 W μm2/cm2 could produce primary, uncollided neutron fluxes at the test specimen in the 1014-1015 n cm-2 s-2 range. While focusing on the laser-plasma interaction physics and resulting neutron production, the materials science required to validate computational damage models utilizing ⩾ 100 dpa irradiation of such specimens is also examined; this may provide a multiscale predictive capability for the behaviour of engineering scale components in fusion reactor applications.

High repetition-rate neutron generation by several-mJ, 35 fs pulses interacting with free-flowing D2O

“…Operating at high intensity (of order 10 19 Wcm −2 ), laser pulse energy is efficiently absorbed in the pre-plasma, generating energetic deuterons. These collide with deuterium nuclei in both the bulk target and the large volume of low density D 2 O vapor surrounding the target to generate neutrons through d (d, n) 3 He reactions. The neutron flux, as measured by a calibrated neutron bubble detector, increased as the laser pulse energy was increased from 6 mJ to 12 mJ.…”

“…Energetic neutrons have numerous applications in many fields, including medicine 1 , homeland security 2 , and material science 3 . Conventional fast neutron sources include deuterium−deuterium (D−D) and deuteriumtritium (D−T) fusion generators, as well as light-ion, photoneutron and spallation sources.…”

Modeling Laser Effects on the Final Optics in Simulated IFE Environments

“…Collaboration with LLNL on development of a pulsed neutron source for IFE and MFE material testing applications (Perkins et al, 2000).…”

Characterisation of deuterium spectra from laser driven multi-species sources by employing differentially filtered image plate detectors in Thomson spectrometers

“…Characterization of the overlapping ion species individually is in many cases important not only in order to understand the underlying acceleration mechanism, but also to facilitate the analysis of any data obtained from secondary processes involving these ion species. This is the case for laser driven deuterium ions (D + ) 17,18 , which are being used to explore the potential of compact, laser-based sources of neutrons [19][20][21] with possible applications in science 22 , industry 23,24 , security 25 or healthcare 26 . The most commonly used targets to produce energetic beams of D + ions are deuterated plastic foils, and a direct measurement of the D + ion spectra with a TPS is non-trivial due to the overlapping C 6+ and O 8+ ions from the target bulk and contaminant layers.…”