arXiv subjects

Mamat Ali Bake

Publications and source records attributed to Mamat Ali Bake.

11 recordsLinked to original sources

arXiv2026

Neutron-source fidelity for laser-driven D--D lithium-blanket tritium-breeding tests

Compact deuterium--deuterium (D--D) neutron sources can provide controllable irradiation fields for lithium-blanket studies, although their broad joint energy and angle distributions differ from the conventional $2.45$~MeV isotropic representation. We couple particle-in-cell (PIC) simulations of target-normal-sheath-accelerated deuterons with a thick-target $D(d,n)^{3}$He source model and Monte Carlo neutron transport. For natural lithium, the seven two-dimensional sources change tritium production per source neutron by $-2.5\%$ to $+54.1\%$ relative to the ideal source. The matched three-dimensional calculation gives an increase of $43.5\%$ and lowers the corresponding ratio from $1.5406$ to $1.4350$. Source substitutions show that the difference is predominantly spectral, since the real spectrum alone gives a factor of $1.4199$, while using the real neutron emission directions in place of isotropic emission adds only a further factor of $1.0106$ in the three-dimensional case. The real spectrum lowers the $^{6}$Li contribution by $6.9\%$, but the accessible $^{7}$Li$(n,Xt)$ response exceeds this loss. Enrichment to $90\%$ $^{6}$Li keeps the total change within $\pm1.5\%$. In the matched three-dimensional converter and blanket calculation, direct $D(d,p)$T production is $0.8458$ tritons per source neutron and accounts for $98.1\%$ and $86.9\%$ of the combined production for natural and enriched lithium, respectively. High-density polyethylene moderation raises tritium production by about one order of magnitude but first weakens and then reverses the increase in blanket tritium production. The analysis quantifies source-model effects in compact breeding tests.

physics.plasm-ph↗

arXiv2026

Multi-objective Bayesian optimisation of a double-layer target for quasi-monoenergetic TNSA protons

We carry out a six-parameter multi-objective Bayesian optimisation of a carbon--hydrogen double-layer target for target-normal-sheath proton acceleration. The campaign consists of 80 two-dimensional EPOCH simulations with the laser amplitude $a_0$, pulse duration $τ$, carbon-layer thickness $L_1$, hydrogen-layer density $N_2$, hydrogen-layer thickness $L_2$ and hydrogen-layer radius $r_p$ as input variables. Each final proton spectrum is scored by the peak energy, the charge fraction inside a $\pm10\%$ peak-energy window and the charge in that window. Among the Pareto-set evaluations, the cases with peak energies between 64 and 71 MeV occur near $a_0=30$, $τ=45$ fs, $L_1=0.3\,μ{\rm m}$, $L_2=30$ nm and $r_p=0.15\,μ{\rm m}$. Along this branch, increasing $N_2$ raises the in-window charge and increases the bandwidth. The small rear-layer radius keeps the proton source within the flat central region of the transverse sheath field, where the accelerating field is nearly uniform. A 3D calculation is performed for the intermediate-density case $N_2=11.85\,n_c$, which balances bandwidth and in-window charge along this branch. The corresponding 2D spectrum has $E_{\rm peak}=67.4$ MeV and $ΔE/E=18.8\%$, whereas the 3D spectrum has $E_{\rm peak}=34.1$ MeV and $ΔE/E=7.0\%$. The lower 3D peak energy and narrower bandwidth are associated with an earlier decay of the rear-sheath field and an earlier saturation of the proton peak energy, and the quasi-monoenergetic peak is retained in 3D.

physics.plasm-ph↗

arXiv2026

Bayesian optimization of double-pulse temporal shaping for enhanced target-normal-sheath proton acceleration under fixed laser energy

Splitting an ultrashort drive pulse into a weak leading pulse and a strong main pulse is known to raise the energy of protons accelerated by the target-normal-sheath-acceleration (TNSA) mechanism, because the leading pulseforms a preplasma that increases the absorption of the main pulse. The allocation of energy between the two pulses and their temporal separation are coupled control parameters, and under a fixed total energy they have not been optimized jointly in a systematic way. We address this problem with two-dimensional particle-in-cell simulations driven by Bayesian optimization. Treating the prepulse energy fraction $r$ and the interpulse delay $Δt$ as free parameters under a fixed total energy, a campaign of 32 simulations, of which 16 are Sobol-initialized and 16 adaptively selected, locates an optimum at $r\approx0.07$ and $Δt\approx234$~fs. The proton cutoff energy increases from 7.7~MeV for the single pulse to 17.7~MeV at the optimum, a gain of about 130\%. The optimum is asymmetric with only about 7\% of the energy in the leading pulse. At the optimum the laser absorption rises from 4.84\% to 20.09\%, the bulk hot-electron temperature from 1.20 to 1.94~MeV, and the time-integrated rear sheath field by a factor of about 1.7. The optimum lies on a broad plateau in $Δt$, which relaxes the timing tolerance required in an experiment.

physics.plasm-ph↗

arXiv2026

A Surrogate Model for Proton Spectrum Prediction to Map Transitions in Laser-Ion Acceleration

We present a physics-guided, decoupled dual-branch surrogate model to predict continuous proton energy spectra from laser-driven ion acceleration. Integrating a $β$-VAE for spectral feature extraction with a parallel multi-layer perceptron for scalar boundary enforcement, the framework achieves a predictive accuracy of $R^2 = 0.94$ for the maximum cutoff energy and $R^2 = 0.94$ for the total particle flux, with a median per-sample spectral $R^2 = 0.985$ (in $\log_{10}$ space) across the full 2000-bin energy distribution. The model incorporates uncertainty quantification via deep ensembles, serving as a quantitative probabilistic diagnostic tool with calibration errors below 6.2\%. Within the 1D longitudinal framework, the surrogate reproduces spectral signatures consistent with the transition from Target Normal Sheath Acceleration (TNSA) to the volumetric heating dynamics of Relativistically Induced Transparency (RIT) and Breakout Afterburner (BOA) regimes, as validated against kinetic diagnostics from 1D particle-in-cell simulations. This approach establishes a computationally efficient baseline for future multi-fidelity optimization and provides an engine for closed-loop parameter control in high-repetition-rate laser facilities.

physics.plasm-ph↗

arXiv2026

Enhancement of Proton Acceleration via Geometric Confinement in Near Critical Density-filled Targets

High-quality proton beams generated by laser-plasma interactions are of significant interest for applications ranging from tumor therapy to fast ignition in inertial confinement fusion. However, simultaneously achieving high energy coupling efficiency and beam collimation remains a challenge. In this work, we investigate the enhancement of proton acceleration via geometric confinement in Near-Critical Density (NCD) plasma-filled micro-structured targets using two-dimensional particle-in-cell (PIC) simulations. To optimize laser-to-particle energy transfer, we systematically compared various target configurations, such as rectangular tubes, hybrid funnels, and straight cones. Our results reveals that increasing geometric complexity does not necessarily translate to superior acceleration performance. Instead, the relatively simple NCD-filled straight-cone target outperforms more complex hybrid geometries, achieving a maximum proton cutoff energy of 181.7 MeV and a reduced divergence of approximately $12^{\circ}$ at a laser intensity of $5.5 \times 10^{20}$ W/cm$^2$. This enhancement is attributed to the synergistic effect of relativistic laser self-focusing within the NCD channel and the strong spatial confinement of hot electrons by the conical walls. Furthermore, we identify a unique double-peak structure in the temporal evolution of the electron energy, which serves as a signature of sustained electron refluxing. This refluxing mechanism maintains a robust sheath field over an extended duration, driving the superior acceleration. The proposed target design offers a robust pathway for generating high-flux, high-energy proton beams suitable for next-generation high-repetition-rate laser facilities.

physics.plasm-ph↗

arXiv2025

Attosecond electron bunch generation by an intense high-order harmonic pulse interacting with a thin target

Laser-accelerated electron bunches and the secondary radiation sources they produce exhibit unique temporal resolution for probing ultrafast physical processes due to their ultrashort pulse duration. The inherently short temporal profile of these pulses leads to extremely high peak bunch currents, thereby enabling a wide range of practical applications. In this study, we propose an innovative method for generating such bunch by utilizing high-harmonics generated through laser-plasma interaction as the driving pulse, which subsequently interacts with a thin target to produce an attosecond electron bunch. Using this method, we successfully generated an electron bunch characterized by excellent collimation and an ultra-short duration of approximately 100 attoseconds, representing a substantial reduction in bunch duration. The total bunch charge achieved was 0.38 nC, with an emittance of $4.5 \times 10^{-3} \, \text{mm} \cdot \text{mrad}$ and a divergence angle of approximately $10^\circ$. Moreover, by systematically analyzing the effects of laser intensity and target positioning, we determined an optimized set of simulation parameters. This research establishes a robust foundation for the generation of ultrashort electron bunches and opens new prospects for their application in advanced high-energy and attosecond physics experiments.

physics.acc-ph↗

arXiv2025

Spin effect in vacuum pair production under two-color rotating electric fields

We investigated the spin effect on the vacuum pair production by Dirac-Heisenberg-Wigner (DHW) formalism under two-color counter-rotating electric fields. We primarily studied the combined effects of the field asymmetry, time delay, and frequency chirp on the particle momentum spectrum with and without considering the spin effect. We have observed that the vacuum pair production process demonstrates spin dependence even in a pure electric field and is sensitive to variations in the field parameters. The results indicate that the spin-dependent momentum spectrum exhibited distinct outcomes for various asymmetric fields with different chirp values and time delay. For an extended asymmetric field with large chirp and time delay, the particle number density can be increased by more than six orders of magnitude. The spin-up and spin-down particles are approximately comparable for a symmetric field with a small-frequency chirp and are dominated by the spin-up particles for a larger chirp. However, in the case of an asymmetric field, the increase in field asymmetry and the chirp parameter lead to a reversal of the spin asymmetry degree. For a shortened asymmetric electric field with a large-frequency chirp, the number of spin-up particles increases, leading to a spin asymmetry degree of $98.62\%$. Conversely, in an extended asymmetric field, the number of spin-down particles increases significantly, which corresponds to a spin asymmetry degree of $99.94\%$.

hep-ph↗

arXiv2025

Vacuum pair production under spatially asymmetric time-oscillating electric fields

We investigate electron-positron pair production from the quantum vacuum in spatially asymmetric, time-oscillating electric fields using the Dirac-Heisenberg-Wigner (DHW) formalism. The field configuration combines spatially separated Sauter-type pulses with temporal oscillations, including frequency chirps and phase modulation. Our results demonstrate that spatial asymmetry significantly enhances pair production compared to symmetric fields, while optimal tuning of temporal parameters (e.g., frequency $ω$ and chirp $b$) further amplifies the yield. For $ω\gtrsim 0.4m$, multiphoton-dominated processes generate oscillatory momentum spectra, whereas low-frequency fields ($ω\lesssim 0.3m$) exhibit tunneling-dominated Gaussian distributions. Chirped fields induce spectral asymmetry and interference patterns, with peak yields increasing by up to a factor of 9 for $ω= 0.7m$ and $b = 0.5ω/τ$. These findings provide a pathway to optimize pair production in experimentally feasible spatiotemporal field configurations.

hep-ph↗

arXiv2025

Effects of driven atomic ensemble on the output spectrum and entanglement of optomechanical system

This paper considers an indirect driving model of a cavity QED system in which the left cavity wall consists of a large ensemble of two-level atoms driven by a classical laser field at a specific resonant frequency, inducing an effective drive for the optomechanical system. We investigate the effects of the atomic ensemble on the output intensity squeezing spectrum and the entanglement between the optical and mechanical modes. Our results show that both the coupling between the atomic ensemble and the cavity mode and the excitation level of the atomic ensemble significantly influences the output spectrum and the entanglement. The theoretical model presented in this paper provides deeper insight into the mechanisms governing correlations and squeezing spectra in conventional optomechanical systems.

quant-ph↗

arXiv2023

Effect of spatially oscillating field on Schwinger pair production

Effect of spatially oscillating fields on the electron-positron pair production is studied numerically and analytically when the work done by the electric field over its spatial extent is smaller than twice the electron mass. Under large spatial scale, we further explain the characteristics of the position and momentum distribution via tunneling time, tunneling distance and energy gap between the positive and negative energy bands in the Dirac vacuum. Our results show that the maximum reduced particle number is about five times by comparing to maximum number for non-oscillating field. Moreover, the pair production results via Dirac-Heisenberg-Wigner formalism can be also calculated by using local density approximation and analytical approximation method when spatial oscillating cycle number is large. Moreover, in case of large spatial scale field, the position distribution of created particles could be interpreted by the tunneling time.

hep-ph↗

arXiv2020

Two stage $γ$ ray emission via an ultrahigh intensity laser pulse interaction with a laser-wakefield accelerated electron beam

We investigate the generation of twin $γ$ ray beams in collision of an ultrahigh intensity laser pulse with a laser wakefield accelerated electron beam by using particle-in-cell simulation. We consider the composed target of a homogeneous underdense preplasma in front of an ultrathin solid foil. The electrons in the preplasma are trapped and accelerated by the wakefield. When the laser pulse is reflected by the thin solid foil, the wakefield accelerated electrons continue to move forward and passing through the foil almost without the influence of the reflected laser pulse and the foil. Consequently, two groups of $γ$ ray flashes, with tunable time delay and energy, are generated by the wakefield accelerated electron beam interacting with the reflected laser pulse from the foil as well as another counter propagating petawatt laser pulse in the behind the foil. The dependence of the $γ$ photon emission on the preplasma densities, driving laser polarization and the foil are studied.

physics.plasm-ph↗