Fig. 1. Schematic of proposed scheme involving two stages: an LS acceleration stage, where a quasi-monoenergetic lithium beam is accelerated by radiation pressure from a femtosecond laser, and a reaction stage, where a directed neutron beam is produced by p(Li7,n) reaction, focused into a cone owing to inverse kinematics.

Fig. 2. Schematic of normal kinematics ⁷Li(p, n) and inverse kinematics p(Li7,n).

Fig. 3. (a) The two solid lines represent the energies of the low-energy neutron group n_0l (blue) and the high-energy neutron group n_0h (red) produced by the reaction p(Li7,n) at θ = 0°. The black dashed line shows the variation of the maximum neutron cone angle with incident lithium ion energy. (b) Total neutron production cross section (top panel) and double differential neutron cross section (bottom panel) at θ = 0°. (c) Stopping power and range for protons in the LiF target and lithium ions in the CH₂ target.

Fig. 4. (a) Ion density isosurface for n_Li = 26n_c and laser field E_y at t = 9T₀ for a laser intensity a = 15.3. (b) and (c) Time evolution of lithium and proton energies, respectively, for different laser intensities indicated by the color key in (b), with the LS model results shown by solid curves and the 3D PIC simulation data by symbols. (d) and (e) Lithium and proton energy spectra, respectively, limited by |y| < 3 μm (solid curves) and cross sections of p(Li7,n) and ⁷Li(p, n) reactions (green dashed curves).

Fig. 5. Monte Carlo simulation results for neutron production. (a) Angular distribution and (b) neutron energy spectrum at a forward angle θ_n < 5° for different laser intensities indicated by the color key in (a). (c) and (d) Energy–angle distributions for inverse and normal kinematics, respectively, at a laser intensity a = 15.3, with the radius representing the neutron energy. (e) and (f) Time spectra of neutron flux arriving at the detector at x = 5 cm for inverse and normal kinematics, respectively. (g) Spatial distribution of neutrons produced in the p(Li7,n) reaction with a = 15.3 at the detector.

Fig. 6. (a) Variations of forward neutron yield (red), low-energy neutron yield (E_n < 4 MeV) (blue), and lithium peak energy (orange) with laser intensity. (b) Variations of forward neutron yield per laser energy (red), low-energy neutron yield (blue) per laser energy, maximum neutron angle (yellow), and beam angle (purple) with laser intensity. (c) Neutron angular spectra produced by TNSA (solid curves) and by LS acceleration results (dashed curves). (d) Neutron angular spectra for inverse (solid curves) and normal (dashed curves) kinematics of the lithium–deuteron reaction.

Fig. 7. (a) Lithium ion density isosurface for n_Li = 26n_c and laser field E_y at time t = 14.0T₀ for a realistic Gaussian laser with intensity a = 15.3 and focal radius σ = 10 μm. (b) Energy spectra of lithium ions near the axis within |y| < 3 μm for a Gaussian laser profile with σ = 10 μm (solid curves) and for a fourth-order super-Gaussian laser profile with σ = 5 μm (dashed curves), at different laser intensities a. (c) Neutron angular distributions and (d) energy spectra of the obtained neutrons with forward angle θ_n < 5° for a realistic Gaussian laser with different intensities indicated by the color key in (b).

Fig. 8. (a) Neutron double differential cross section of ⁷Li(p, xn) and p(Li7,xn) at θ = 0° used in the MCNRC code, compared with experimental data.^55,56 (b) Comparison of the total neutron yield calculated by the MCNRC code with results of numerical calculation.⁵⁷ (c) Neutron spectra simulated by the MCNRC code covering the forward 10° produced by 4 μm-thick CH₂ targets with different lithium energies, with different energy values labeled on the peak positions, which are in good agreement with numerical results.²¹ (d) Double differential cross sections at 0° of the ⁷Li(d, xn) reaction in the JENDL-DEU database. (e) Comparison of neutron energy spectra of ⁷Li(d, xn) reactions at E_d = 13.4 MeV between MCNRC simulations and experimental results of Takeshita et al.⁴⁴