Neutron production from thermonuclear reactions in laser-generated plasmas

Abstract

The production of intense neutron beams via thermonuclear reactions in laser-generated plasmas is investigated theoretically. So far, state-of-the-art neutron beams are produced via laser-induced particle acceleration leading to high-energy particle beams that subsequently interact with a secondary target. Here we show that neutron beams of similar intensity and two orders of magnitude narrower bandwidth can be obtained from thermonuclear reactions in plasmas generated by Petawatt-class lasers. We study to this end the reaction 2 H(d, n) 3 He in plasmas generated by Petawatt-class laser interacting with D2 gas jet targets and CD2 solid-state targets. The use of CD2 solid-state targets can also allow the direct measurement of the nuclear reaction rates at low temperatures and show great enhancement on the plasma screening comparing to the case of D2 gas jet targets, opening new possibilities to study these two so far unsolved issues in the field of astrophysics.Thermonuclear reactions occur in plasma environments in which the thermal energy of the ions can overcome the electrostatic repulsion in a collision between nuclei, leading to nuclear reactions [1]. The development of laser technology in the past decades provides a powerful tool for the study of nuclear reactions in laser-generated plasmas. As plasma is the most abundant form of matter in the universe, the latter provides the opportunity to access parameter regimes which can not be accessed in accelerator-based experiments, such as the direct measurements of nuclear reactions in nucleosynthesis-relevant energies and the role of the plasma effects on nuclear reactions [2-5], and might thus significantly advance our understanding of astrophysical environments. On the other hand, industrial applications of such studies, such as laser-induced ignition which makes fusion energy a viable alternative energy source [5][6][7], have also attracted a great deal of attention.Neutron production is one of the key areas of the field of nuclear reactions in laser-generated plasmas [8][9][10][11][12][13]. Normally the experimental access to high neutron flux is mainly at large-scale reactor and accelerator-based facilities. However, the development of Petawatt-class laser provides the opportunity of having intense neutron beam generated by comparatively smaller-scale laser facilities [11][12][13]. The common solution for neutron production in the Petawatt-class laser facilities is via high-energy particle beams interacting with a secondary target, in which the lasers are used for the acceleration of particles [11][12][13]. In this manner, intense neutron beams with the order of 10 9 -10 10 per pulse can be obtained [11][12][13].Neutrons produced from thermonuclear reactions in plasmas at a few keV temperatures have a much narrow energy spectrum comparing to the neutrons produced via high-energy ion beams interacting with a secondary target. In this letter, we study the intense neutron beams produced from thermonuclear reactions in laser-generated plasmas. We analyze the rea...

Quantum effects on plasma screening for thermonuclear reactions in laser-generated plasmas

“…The predicted values for n i = 10 21 cm −3 show that also for the 2 H(d, n) 3 He reaction, the screening effect would be negligible in gas-jet experiments which are bound to low ion density values, as already implied in Ref. [49]. For higher plasma densities, the DMF model provides the largest screening factor, while the Mitler formula gives the smallest one.…”

“…Both X-ray Free Electron Lasers (XFELs) [35][36][37][38] and ultra-strong optical lasers [39][40][41][42][43][44] open so-far unavailable parameter regimes for the study of nuclear physics in laser-generated plasmas [3,7,28,[45][46][47]. Theoretical works have shown that experiments at petawatt optical lasers allow tests of the widely used Salpeter weak screening model for thermonuclear reactions [48,49]. This Letter moves to investigate the quantum plasma effect in laser-generated plasmas in the intermediate screening regime of low temperature and high density, which should come into the experimental reach of present laser facilities.…”

Fluctuation-induced inward particle flux during L–I–H transition on HL-2A tokamak

“…This coherent mode has been identified as the LLM, a kind magnetohydrodynamic (MHD) mode, on the HL-2A tokamak [19,32]. According to amplitude profiles of SXR fluctuation for this coherent mode, the LLM is generated at the core plasma (r = 16.2 cm) which reconfirms that this coherent mode is indeed LLM [27].…”

“…Density and electric field fluctuation measurements are carried out by the radially reciprocating probe system. The fast reciprocating Langmuir probe array contains two poloidally separated probe arrays A and B at a distance of 80 mm [27]. The probe array A includes two standard four-tip probes which are radially separated by Δ r = 2 mm, and a pair of Mach probe in the toroidal direction.…”

“…In this discharge, the L-I-H transition is distinctly distinguished from the D α signal representing the recycling state, as shown in figures 1(c) and 2(a). The reciprocating probe array inserts the plasma via a port located on the low field side vacuum vessel midplane and stays steady at r = 35.5 cm during the entire L-I-H transition [27]. As a typical H-mode discharge, the electron density increases, and the radial electric field becomes sharply negative at the edge when the plasma enters the H-mode state, as shown in figures 2(d) and (e).…”