Speaker
Description
Generation of neutrons from laser-based sources has been the focus of research and development for over two decades. The first step towards generating fusion neutrons is to accelerate ions with sufficient kinetic energy to overcome the repulsive Coulomb potential. So far, most of the ion acceleration experiments have been carried out using multi-cycle, Joule-class lasers. Although the number of neutrons produced in a single laser shot is high, the low repetition rate of such lasers results in a modest average neutron yield (number of neutrons per second) from these systems.
Most of the applications, including nuclear resonance spectroscopy, neutron imaging, isotope production, and transmutation of minor actinides in spent nuclear waste, require a (quasi) continuous source of neutrons operating in a 24/7 mode. Recent developments of few-cycle laser systems with an average optical power of 100 W have laid the technological basis for the development of such a neutron source.
Upon our experimental series conduced at ELI-ALPS in Hungary, first we have demonstrated that ions can be accelerated efficiently with laser pulses of few 10’s mJ energy and few-optical cycle pulse duration [1]. Next, ultrathin deuterated foil targets were fixed to a rotating wheel target system, so that deuterons were accelerated at 1Hz repetition rate in burst of 75 shots. The accelerated deuterons generate neutrons via DD fusion reaction in a deuterated PE tablet. The energy and spatial distribution of the fast neutron beam were characterized by a Time-of-flight (ToF) neutron detector system. The experimental data, comprising more than 3000 laser shots, shows that the neutron conversion efficiency (number of neutron / laser Joule) from our few-optical cycle laser is comparable to that of PW class lasers [2].
Most recently, with the development of an ultrathin liquid sheet target system, it become possible to operate the laser deuteron accelerator continuously for more than six hours at 10 Hz repetition rate. The neutron flux well exceeded 10$^5$ neutron / sec, confirmed by a bubble detector system, too. In a further step, the kHz repetition rate SYLOS laser is to be used, so that a laboratory sized, laser-based neutron source of 10$^7$ – 10$^8$ neutron / second will be available.
This research is supported by the National Research, Development, and Innovation Office of Hungary through the National Laboratory program (contract # NKFIH-877-2/2020, NKFIH-476-4/2021).
[1] S. Ter-Avetisyan et al., “Ion acceleration with few cycle laser pulses” PPCF 65, 085012 (2023).
[2] K. Osvay et al., “Fast neutron generation with few-cycle, relativistic laser pulses at 1 Hz repetition rate,” Sci.Rep., submitted
