Explore the vast range of titles available.

Boron neutron capture therapy (BNCT) was first proposed as early as 1936, and research on BNCT has progressed relatively slowly but steadily. BNCT is a potentially useful tool for cancer treatment that selectively damages cancer cells while sparing normal tissue. BNCT is based on the nuclear reaction that occurs when 10 B capture low-energy thermal neutrons to yield high-linear energy transfer (LET) α particles and recoiling 7 Li nuclei. A large number of 10 B atoms have to be localized within the tumor cells for BNCT to be effective, and an adequate number of thermal neutrons need to be absorbed by the 10 B atoms to generate lethal 10 B (n, α) 7 Li reactions. Effective boron neutron capture therapy cannot be achieved without appropriate boron carriers. Improvement in boron delivery and the development of the best dosing paradigms for both boronophenylalanine (BPA) and sodium borocaptate (BSH) are of major importance, yet these still have not been optimized. Here, we present a review of this treatment modality from the perspectives of radiation oncology, biology, and physics. This manuscript provides a brief introduction of the mechanism of cancer-cell-selective killing by BNCT, radiobiological factors, and progress in the development of boron carriers and neutron sources as well as the results of clinical study.

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.

Several neutron sources are available at Research Centre Řež (CVŘ) that are usable in neutron physics and radioanalytical measurements, namely two experimental nuclear reactors—a ‘zero’ power (maximum 5 kW) LR-0 reactor and a medium power (maximum 10 MW) LVR-15 reactor, a 252 Cf source and a D–T generator of fast neutrons. Their basic parameters and modes of applications in various fields of science and technology are described. The reactors and other neutron sources are equipped with a number of gamma-ray (mostly High Purity Germanium (HPGe)), and neutron spectrometers to allow for assay of studied materials. Most of the above facilities are available in an open-access regime.

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.

Recently, progress in technology for accelerator-based neutron sources has increased attention regarding boron neutron capture therapy (BNCT). BNCT is a type of radiotherapy that combines neutrons and boron drugs and is expected to be used in the treatment of refractory and recurrent cancers. Owing to the need for high-intensity neutrons in treatment, compact accelerator-based neutron sources applicable to BNCT are being developed worldwide. These current projects utilize cyclotrons, linear accelerators, and electrostatic accelerators as accelerators for BNCT devices. Beryllium and lithium are the main target materials for neutron generation. The accelerators for BNCT device are required to accelerate charged particles with an average current ranging from a few milliamperes to a few tens of milliamperes in order to generate neutrons of sufficient intensity for the treatment. Moreover, the target systems require technologies and mechanisms that can withstand the large heat load produced by high-power beam irradiation and prevent blistering. This review outlines and explains the accelerator neutron sources for BNCT and the requirements for the components of each device, such as the accelerator, target material, and beam shaping assembly. In addition, various development projects for accelerator-based BNCT devices worldwide are introduced.

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.

The application of a controllable neutron source for measuring formation porosity in the advancement of nuclear logging has garnered increased attention. The existing porosity algorithm, which is based on the thermal neutron counting ratio, exhibits lower sensitivity in high-porosity regions. To enhance the sensitivity, the effects of elastic and inelastic scattering, which influence the slowing-down of fast neutrons, were theoretically analyzed, and a slowing-down model of fast neutrons was created. Based on this model, a density correction porosity algorithm was proposed based on the relationship between density, thermal neutron counting ratio, and porosity. Finally, the super multifunctional calculation program for nuclear design and safety evaluation (TopMC/SuperMC) was used to create a simulation model for porosity logging, and its applicability was examined. The results demonstrated that the relative error between the calculated and actual porosities was less than 1%, and the influence of deviation in the density measurement was less than 2%. Therefore, the proposed density correction algorithm based on the slowing-down model of fast neutrons can effectively improve the sensitivity in the high-porosity region. This study is expected to serve as a reference for the application of neutron porosity measurements with D–T neutron sources.

The cold neutron imaging and diffraction instrument IMAT at the second target station of the pulsed neutron source ISIS is currently being commissioned and prepared for user operation. IMAT will enable white-beam neutron radiography and tomography. One of the benefits of operating on a pulsed source is to determine the neutron energy via a time of flight measurement, thus enabling energy-selective and energy-dispersive neutron imaging, for maximizing image contrasts between given materials and for mapping structure and microstructure properties. We survey the hardware and software components for data collection and image analysis on IMAT, and provide a step-by-step procedure for operating the instrument for energy-dispersive imaging using a two-phase metal test object as an example.

A novel concept of cold neutron source employing chessboard or staircase assemblies of high-aspect-ratio rectangular para-hydrogen moderators with well-developed and practically fully illuminated surfaces of the individual moderators is proposed. An analytic approach for calculating the brightness of para-hydrogen moderators is introduced. Because the brightness gain originates from a near-surface effect resulting from the prevailing single-collision process during thermal-to-cold neutron conversion, high-aspect-ratio rectangular cold moderators offer a significant increase, up to a factor of 10, in cold neutron brightness compared to a voluminous moderator. The obtained results are in excellent agreement with MCNP calculations. The chessboard or staircase assemblies of such moderators facilitate the generation of wide neutron beams with simultaneously higher brightness and intensity compared to a para-hydrogen-based cold neutron source made of a single moderator (either flat or voluminous) of the same cross-section. Analytic model calculations indicate that gains of up to approximately 2.5 in both brightness and intensity can be achieved compared to a source made of a single moderator of the same width. However, these gains are affected by details of the moderator–reflector assembly and should be estimated through dedicated Monte Carlo simulations, which can only be conducted for a particular neutron source and are beyond the scope of this general study. The gain reduction in our study, from a higher value to 2.5, is mostly caused by these two factors: the limited volume of the high-density thermal neutron region surrounding the reactor core or spallation target, which restricts the total length of the moderator assembly, and the finite width of moderator walls. The relatively large length of moderator assemblies results in a significant increase in pulse duration at short pulse neutron sources, making their straightforward use very problematic, though some applications are not excluded. The concept of “low-dimensionality” in moderators is explored, demonstrating that achieving a substantial increase in brightness necessitates moderators to be low-dimensional both geometrically, implying a high aspect ratio, and physically, requiring the moderator’s smallest dimension to be smaller than the characteristic scale of moderator medium (about the mean free path for thermal neutrons). This explains why additional compression of the moderator along the longest direction, effectively giving it a tube-like shape, does not result in a significant brightness increase comparable to the flattening of the moderator.

Neutron beams, being electrically neutral and highly penetrating, offer unique advantages for the irradiation of biological species such as plants, seeds, and microorganisms. We comprehensively investigated the potential of neutron irradiation for inducing genetic mutations by using simulations of spallation, reactor, and compact neutron sources based on J-PARC BL10, the JRR-3 TNRF, and KUANS. We analyzed neutron flux, energy deposition rates, and Linear Energy Transfer (LET) distributions. The KUANS simulation demonstrated the highest dose rate of 17 Gy/h, significantly surpassing that obtained at BL10, due to the large solid angle achieved with optimal sample placement. The findings highlight KUANS’s suitability for efficiently inducing specific genetic mutations and neutron breeding, particularly for inducing targeted mutations in biological samples, also on account of its LET range of 20–70 keV/μm. Our results emphasize the importance of choosing neutron sources based on LET requirements to maximize mutation induction efficiency. This research study shows the potential of compact neutron sources such as KUANS for effective biological irradiation and neutron breeding, offering a viable alternative to larger facilities. The neutron filters used at BL10 and the TNRF effectively exclude low-energy neutrons while keeping the high-LET component. The neutron capture reaction, 14N(n,p)14C, was found to be the main dose contributor under thermal neutron-dominated conditions.