Abstract
With the phasing out of many research reactors over the upcoming years, a shortcoming of small and medium sized neutron sources is to be expected. Laser-driven neutron sources have the potential to fill this void, with enormous progress being made in laser technology over the past years. Upcoming petawatt lasers with high repetition rates up to 10 Hz promise a tremendous increase in neutron flux. In this paper, a setup is developed and optimized to conduct neutron resonance spectroscopy at a laser-driven neutron source. This setup is then evaluated at an experimental campaign at the PHELIX laser system. Laser intensities up to 1021 W/cm² with a ns pre-pulse contrast of 10-7 were used for ion acceleration, resulting in (1.8±0.7)×108 N/sr per pulse corresponding to (2.3±1.0)×109 N in a 4 π equivalent. These pulses were moderated, collimated and investigated via the time of flight method in order to characterize the thermal neutron spectrum as well as the signal to noise ratio.
Highlights
Neutrons provide a unique tool for material analysis, from neutron diffraction [1] over prompt gamma neutron activation analysis [2] to Neutron Resonance Spectroscopy (NRS) [3]
Neutrons were in many cases provided by research reactors
During the operation of an Laser-Driven Neutron Sources (LDNS), the beryllium catcher has to be shielded against ablation by the expanding hot laser plasma, since beryllium dust is highly toxic and the integrity of the catcher has to be maintained
Summary
Neutrons provide a unique tool for material analysis, from neutron diffraction [1] over prompt gamma neutron activation analysis [2] to Neutron Resonance Spectroscopy (NRS) [3]. These techniques can be used to identify the elemental and isotopic compositions of unknown materials without compromising the structural integrity of the sample. A large fraction of these sources have been or will be shut down in the near future and a need for small and medium-sized neutron sources is growing [4]. Recent improvements in laser technology enable high-intensity lasers to be operated up to 10 Hz [6], tremendously increasing the average neutron flux of these sources
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