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Designing and optimizing target structures is one of the most critical steps in high‐intensity laser experiments, like laser‐driven neutron sources, which are increasingly recognized for their compactness and portability. Herein, an artificial intelligence (AI)‐assisted target design approach that leverages AI algorithms in combination with particle‐in‐cell simulations is proposed. This newly AI‐optimized structure addresses the limitations of conventional approaches, such as foam targets or wire‐array structures. Simulation results demonstrate a neutron yield exceeding three orders of magnitude compared to flat targets and over 18 times greater than that of wire‐array targets. This dramatic result demonstrates that the AI‐assisted target design method can be effectively applied to other high‐intensity laser applications. This study presents an artificial intelligence (AI)‐assisted target design that combines particle‐in‐cell simulations with gradient ascent algorithm to optimize laser‐driven neutron sources. By enhancing the sheath electric field, the optimized structure increases neutron yield by a factor of 4,000. These results demonstrate the potential of AI in developing compact, high‐yield neutron sources, as well as other high‐intensity‐laser related fields.

Laser-driven neutron sources (LDNS) are an emerging technology with significant potential. The most promising types of LDNS are based on laser wakefield acceleration or target normal sheath acceleration, driven in a “pitcher-catcher” configuration. In this publication, we estimate the performance of LDNS once they have been optimized for industrial-scale usage and identify for which applications they can be used. For this purpose, we evaluate the current laser developments and identify the three most promising laser systems that can be used to cover the most relevant applications. A scaling system is then derived to predict the neutron production rate for each of the three systems. The first system is expected to produce 8 × 10 8 n s - 1 to 8 × 10 9 n s - 1 for thermalized neutrons. The second one 1 × 10 11 n s - 1 for fast neutrons and the third one 1 × 10 14 n s - 1 to 1 × 10 15 n s - 1 fast neutrons. This is followed by an evaluation of possible applications that can be driven with each of the different LDNS system. We conclude with a comparison of the scaling law and the neutron production rate to existing experimental data and scaling laws from other groups to evaluate the accuracy of the model and the estimates for the different applications.

We predict the production yield of a medical radioisotope ^{67}$ Cu using ^{67}$ Zn(n, p) ^{67}$ Cu and ^{68}$ Zn(n, pn) ^{67}$ Cu reactions with fast neutrons provided from laser-driven neutron sources. The neutrons were generated by the p+ ^9\\mathrm{Be}$ and d+ ^9$ Be reactions with high-energy ions accelerated by laser–plasma interaction. We evaluated the yield to be (3.3 $\\pm$ 0.5) $\\times$ 10 ^5$ atoms for ^{67}$ Cu, corresponding to a radioactivity of 1.0 $\\pm$ 0.2 Bq, for a Zn foil sample with a single laser shot. Using a simulation with this result, we estimated ^{67}$ Cu production with a high-frequency laser. The result suggests that it is possible to generate ^{67}$ Cu with a radioactivity of 270 MBq using a future laser system with a frequency of 10 Hz and 10,000-s radiation in a hospital.

The advance of laser-driven neutron sources (LDNSs) has enabled neutron resonance spectroscopy to be performed with a single shot of a laser. In this study, we describe a detection system of epithermal (∼eV) neutrons especially designed for neutron resonance spectroscopy. A time-gated photomultiplier tube (PMT) with a high cut-off ratio was introduced for epithermal neutron detection in a high-power laser experiment at the Institute of Laser Engineering, Osaka University. We successfully reduced the PMT response to the intense hard X-ray generated as a result of the interaction between laser light and the target material. A time-gated circuit was designed to turn off the response of the PMT during the laser pulse and resume recording the signal when neutrons arrive. The time-gated PMT was coupled with a 6Li glass scintillator, serving as a time-of-flight (TOF) detector to measure the neutron resonance absorption values of 182W and 109Ag in a laser-driven epithermal neutron generation experiment. The neutron resonance peaks at 4.15 eV of 182W and 5.19 eV of 109Ag were detected after a single pulse of laser at a distance of 1.07 m.

Neutron sources based on laser-accelerated particles have attracted interest as they may provide a compact, cost-effective alternative to conventional sources. Recently, laser-driven neutron sources, based on ion acceleration, demonstrated neutron resonance spectroscopy, imaging and resonance imaging in first proof-of-principle experiments. To drive these sources efficiently with laser-accelerated ions, high laser pulse energies, in the range of tens to hundreds of Joules, with sub-ps pulse duration are needed. This requirement currently limits ion-based laser neutron sources to large-scale laser systems, which typically have maximum repetition rates in the order of a few shots per hour. In this paper, we investigate a potential path to circumvent these limitations by utilizing high repetition rate capable laser wakefield acceleration of electrons to drive a neutron source with high conversion efficiency. Monte Carlo simulations are performed to calculate neutron yields for various electron energies and converter materials, to determine optimal working parameters for an electron-based laser-driven neutron source. The results suggest that conversion efficiencies exceeding 25% can be achieved, depending on the electron energy and converter material. This electron-based approach could provide a neutron source with up to 10 11 n/s with state-of-the-art laser sources ( E Laser ≲ 1 J , τ Laser ≲ 50 fs , ∼ 1 kHz ).

Since two decades, laser-driven neutron emissions are studied as they represent a complementary source to conventional neutron sources, with further more different characteristics (i.e. shorter bunch duration and higher number of neutrons per bunch). We report here a global, thorough characterization of the neutron fields produced at the Apollon laser facility using the secondary laser beam (F2). A double plasma mirror (DPM) was used to improve the temporal contrast of the laser which delivers pulses of 24 fs duration, a mean on-target energy of ∼ 10 J and up to 1 shot/min. The interaction of the laser with thin targets (few tens or hundreds of nm) in ultrahigh conditions produced enhanced proton beams (up to 35 MeV), which were then used to generate neutrons via the pitcher-catcher technique. The characterization of these neutron emissions is presented, with results obtained from both simulations and measurements using several diagnostics (activation samples, bubble detectors and Time-of-Flight detectors), leading to a neutron yield of ∼ 4 × 10 7 neutrons/shot . Similar neutron emissions were observed during shots with and without DPM, while fewer X-rays are produced when the DPM is used, making this tool interesting to adjust the neutrons/X-rays ratio for some applications like combined neutron/X-ray radiography.

A project has been launched for the development of a laser-based neutron source with the few-cycle lasers available at ELI ALPS. Here we show the first experiments, when deuterons were accelerated from ultrathin deuterated foils at 1 Hz repetition rate with the use of 12 fs, 21 mJ laser pulses. The energy spectra of the accelerated deuterons were measured with Thomson ion spectrometers both in forward and backward directions. The accelerated deuterons induced 2 H +  2 H fusion reaction in a deuterated polyethylene disk. The resulting fast neutrons were measured with a time-of-flight (ToF) detector system, within which each detector consisted of a plastic scintillator and a photomultiplier, at four different angles relative to the normal of the neutron converter disk. We found good agreement with the simulated angular distribution and energy spectra. Here, we also present preparations for the next phases when the repetition rate is increased to 10 Hz. The developed flat liquid jet was demonstrated to accelerate protons over 0.6 MeV cutoff energy with a stability better than 4% for 15 min. We developed two further neutron measurement techniques: a liquid scintillator, the ToF signal of which was evaluated with the pulse shape discrimination method, and a bubble detector spectrometer calibrated against a conventional PuBe source. One of the first upcoming applications is the irradiation of zebrafish embryos with laser-generated ultrashort bunch neutrons. As this experiment needs to be implemented in vacuum, the steps of careful preparation and calibration measurements are also discussed.

We present repeated generation of photoneutrons by double-pulse irradiation of ultrathin foils. A ~ mJ prepulse turns a foil into a 100-μm scale plasma plume from which a beam of MeV electrons is generated by the main pulse. Neutrons are generated in a secondary metal target placed downstream to the electron beam. We utilize an automated target system capable of delivering ultrathin foils to the laser focus at an average rate of 0.1 Hz. With 153 consecutive laser shots taken over the course of 24 min, we generated a total 2.6 × 10 7 neutrons. We present a method for evaluating how the number of photoneutrons scales with the laser intensity in this experimental scenario, which we validate against the measured yields.

A novel scheme for generating high-flux neutron beams via collisionless shock acceleration is proposed, where a subpicosecond laser pulse interacts with a practical gas cell target composed of uniform deuteron gas and a solid foil covering the front of the cell. When the heated foil expands into the low-density gas, a strong electrostatic field induced by hot electrons rolls up the gas deuterons, compressing them into a high-density peak while accelerating them to supersonic speeds. This process would spontaneously launch a strong collisionless shock wave, without the need for a specific plasma profile. Copious upstream deuterons will be continuously reflected and accelerated to high energies. Once the laser pulse penetrates the thin foil due to relativistic transparency, the shock velocity and the reflected deuteron energies are further enhanced. By combining two-dimensional particle-in-cell and three-dimensional Monte Carlo simulations, we demonstrate that by utilizing a LiF catcher target, a high-flux collimated neutron beam with yield per unit solid angle exceeding 10 10   n sr − 1 is generated via 7 L i ( d , x n ) reactions driven by a subpicosecond laser pulse at an intensity of 8.8 × 10 19   W cm − 2 , six times higher than that from a typical foil target without deuterium gas. This simple approach overcomes the challenges of controlling the density profiles in conventional ablation schemes, paving the way for laser-driven compact neutron sources.

Laser-driven ion sources are approaching the requirements for several applications in materials and nuclear science. Relying on compact, table-top, femtosecond laser systems is pivotal to enable most of these applications. However, the moderate intensity of these systems (I 1019 W cm−2) could lead to insufficient energy and total charge of the accelerated ions. The use of solid foils coated with a nanostructured near-critical layer is emerging as a promising targeted solution to enhance the energy and the total charge of the accelerated ions. For an appropriate theoretical understanding of this acceleration scheme, a realistic description of the nanostructure is essential, also to precisely assess its role in the physical processes at play. Here, by means of 3D particle-in-cell simulations, we investigate ion acceleration in this scenario, assessing the role of different realistic nanostructure morphologies, such as fractal-like foams and nanowire forests. With respect to a simple flat foil, the presence of a nanostructure allows for up to a × 3 increase of the maximum ion energy and for a significant increase of the conversion efficiency of laser energy into ion kinetic energy. Simulations show also that the details of the nanostructure morphology affect both the maximum energy of the ions and their angular distribution. Furthermore, combined 3D particle-in-cell and Monte Carlo simulations show that if accelerated ions are used for neutron generation with a beryllium converter, double-layer nanostructured targets allow to greatly enhance the neutron yield. These results suggest that nanostructured double-layer targets could be an essential component to enable applications of hadron sources driven by compact, table-top lasers.