7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Simulation Study of Laser Proton Acceleration in a Gas Target
Sz-Jie Lee, Jou-Yu, Lu and Shih-Hung Chen*
Department of physics, National Central University, Taoyuan City 320317, Taiwan*e-mail: chensh@ncu.edu.tw
The use of high-energy protons and boron targets toproduce nuclear fusion reactions does not produce
neutrons [1], making this nuclear fusion reaction safer andless polluting. In addition, hydrogen and boron are botheasily available materials and cheap, so research related tohydrogen-boron nuclear fusion reaction has recently
become an important scientific research topic.
The hydrogen-boron nuclear reaction rate at a plasma
ion temperature of 10 keV is several orders of magnitude
smaller than the deuterium-tritium nuclear reaction rate[2]. To achieve a similar nuclear reaction rate, thetemperature of hydrogen-boron plasma must be higher
than 100 keV. However, it is not easy to maintain thistemperature in a magnetically confined plasma, but
experiments have proven the feasibility of using laser
acceleration of protons to trigger proton-boron fusion
reactions [3]-[4]. Therefore, laser acceleration of protons
becomes a concrete and feasible way to trigger thehydrogen-boron fusion reaction.
Technologies related to the use of high field lasers andsolid targets to generate proton beam acceleration havebeen studied for many years [5]. Currently, experiments
can produce proton acceleration of approximately 100
MeV energy [6]. However, due to limitations in target
production and laser pulse shaping technology andpollution due to the debris produced by the broken solidtarget, the gaseous target has become a good alternative[7]. However, using gaseous targets requires increasing
the laser wavelength, so CO2 laser is the best choice.
However, there are currently not many short-pulse andhigh-intensity CO2 laser facilities. Fortunately, the proton
beam energy required for the hydrogen-boron fusion
reaction is around a few MeV. Therefore, National Central
University is building a 10-ps 1.5-J CO2 laser system forresearch on hydrogen-boron fusion reactions.
Therefore, particle-in-cell simulation is performed in
the study to estimate the proton energy generated by theinteraction of this laser pulse with the 100-µm hydrogentarget. Preliminary simulation results show that circularly
polarized laser fields can produce better proton beam
quality, and the proton beam energy can reach several
MeV. The scaling of the proton beam energy with laser
intensity and plasma density can also confirm that its
acceleration mechanism is hole-boring acceleration [8].
However, the simulation study also demonstrated that thecollisional ionization process has a great impact on theproton acceleration process within a specific laser
intensity range, and the generated protons will split into
high-energy and low-energy groups. The physical reasonsfor the phenomena will be explained in the report.
References[1] Fabio Belloni, “Multiplication Processes in HighDensity H-11B Fusion Fuel,” Laser and Particle
Beams
2022,
ArticleID
3952779:https://doi.org/10.1155/2022/3952779.
[2] Samuel E. Wurzel and Scott C. Hsu, Phys. Plasmas 29,062103 (2022).
[3] Lifschitz, A. F., Farengo, R. & Arista, N. R. Ionization,stopping, and thermalization of hydrogen and boron
beams injected in fusion plasmas. Phys. Plasmas 7,3036–3041 (2000).
[4] Labaune, C.; Baccou, C.; Depierreux, S.; Goyon, C.;
Loisel, G.; Yahia, V.; Rafelski, J., “Fusion reactions
initiated by laser-accelerated particle beams in a laserproduced plasma,” Nat. Commun. 4, 2506 (2013).
[5] Macchi, A.; Borghesi, M.; Passoni, M. Ion acceleration
by superintense laser-plasma interaction. Rev. Mod.
Phys. 85, 751 (2013).
[6] Higginson, A., Gray, R.J., King, M. et al. Near-100
MeV protons via a laser-driven transparencyenhanced hybrid acceleration scheme, Nat. Commun.
9, 724 (2018).
[7] Tung-Chang Liu et. al., New J. Phys. 17, 023018(2015).
[8] C. Palmer et. al., PRL 106, 014801 (2011).