7Be Reaction Research Articles

Boron neutron capture therapy: History and recent advances

In this article, we looked at ‘Boron Neutron Capture Therapy (BNCT)’, a possible cancer treatment plan in which boron chemicals are selectively concentrated in tumor cells before being exposed to ‘epithermal neutron beam radiations. The idea is different from previous neutron-based therapies in that, it allows for more precise tumor removal and has been tried on a range of malignancies, including deep-seated and skin cancers. Neutrino-controlled catalysis has been chastised for its lack of clinical trials, poor outcomes, and the fact, that it requires radiation that can be produced in nuclear research reactors. In 1950, BNCT was first used on patients at the ‘Massachusetts Institute of Technology (MIT)’ and it was later banned in the United States in 1961.Simple inorganic compounds of boron were used in three series of therapies on forty patients (up to 1961), with different degrees of success and failure. BNCT is a spectacular assemblage of nuclear technology, chemistry, biology, and medicine in the fight against cancer. Three concepts for a BNCT accelerator-based neutron source were presented in 1998. The 7Li, 7Be reaction was chosen as the third choice, despite its poor melting point and thermal conductivity. A plan has been established for the future, but putting it into effect will be difficult. BNCT is most effective when combined with other therapies like surgery, chemotherapy, and external beam radiation therapy. Physicians and scientists must collaborate to find a way out of the current stalemate.

Isomeric yield ratio of 115m,gCd in the 116Cd(γ,n) and 116Cd(n,2n) reactions

The isomeric yield ratio (IR) of 115m,gCd in the 116Cd(γ,n) reaction at the bremsstrahlung endpoint energies of 70 and 75 MeV and in the 116Cd(n,2n) reaction at the average neutron energies (<En > ) of 21.4 and 30.1 MeV were measured via an offline γ -ray spectrometric technique. The bremsstrahlung energies were produced by impinging the electron beam energies of 70 and 75 MeV on a thin W-target at the Pohang Accelerator Laboratory, Korea. The neutron beams were obtained from the 9Be(p,n) reaction with the proton energies of 35 and 45 MeV using the MC-50 cyclotron at the Korean Institute of Radiological and Medical Sciences. The IR values at different bremsstrahlung and neutron energies were also calculated from the cross-section values of the TENDL-2019 library based on the TALYS-1.9 code. The theoretical values agreed with the experimental data for the bremsstrahlung endpoint energies but were slightly higher for all neutron energies. The current and literature data showed that in both the 116Cd(γ,n) and 116Cd(n,2n) reactions, the IR value of 115m,gCd increases with the projectile energy, indicating the role of excitation energy. However, the experimental and theoretical IR values at the same excitation energy were significantly higher for the 116Cd(n,2n) reaction than that for the 116Cd(γ,n) reaction, highlighting the role of compound nucleus spin.

A feasibility study of SMART reactor power performance optimizations-part 2: Reflector material selection

The neutron reflector is a general component in the nuclear reactor design. The original SMART reactor design used light water as a reflector surrounding the fission zone. However, this design has low uranium utilization rates in the outermost fuel assemblies, so poor fuel economy. In this study, six potential reflector materials, i.e., heavy water, graphite, beryllium metal and its oxide, steel, and tungsten carbide has been investigated as the neutron reflector for SMART. Firstly, the materials’ cross-sections of neutron scattering and (n, 2n) reactions have been cited from ENDF data libraries and analyzed. This analysis found for the neutrons with energy lower than 1 eV, the 9Be atom has six barn elastic scattering cross-sections, and the 9Be(n, 2n)8Be reaction can compensate for neutron leakage. Then, OpenMC is employed to simulate the effect of these reflector materials on power distribution and depletion. Compared with the original design, the beryllium oxide can improve the initial keff from 1.22906 to 1.27446, flat the radial direction power distribution. The analysis on both scales agrees that the beryllium oxide is an efficient neutron reflector choice with good material properties.

Design of a compact RFQ linac for the transportable neutron source

A transportable accelerator-driven neutron source based on the Radio Frequency Quadrupole (RFQ) linac is developing at Xi’an Jiaotong University (X-TANS). It will be a promising tool for the non-destructive inspection of immovable objects. The neutron yield above 10 11n/s can be obtained via 7Li(p,n)7Be reaction with a proton beam energy of 2.5 MeV. To exactly guarantee the transportability of the neutron source, it is essential to achieve the light, compact and low-power consumption of RFQ linac. The operation frequency of 325 MHz is chosen considering the balance among cavity size, cavity consumption, and electrode aperture. In addition, compact dynamics scheme is adopted to achieve short RFQ by sacrificing a beam bunching efficiency. The beam dynamics design and optimization have been performed based on Parmteqm. Beam tracking results show that RFQ can accelerate the proton beam to 2.5 MeV with an electrode length of 2.6 m and an effective transmission efficiency of 93.8%. To enlarge the redundancy of the input beam mismatch and make the beam match easier from LEBT to RFQ, the electrode aperture is designed to shrink gradually in the RFQ entrance. In addition, we also performed the RF electromagnetic design and optimization based on the full-length 3D RFQ model. Multiphysics simulations of the cavity in different working conditions are investigated at last.

Effects of energy levels of the compound nucleus on particle emission for the 6Li(n,t), 3He(n,p), and 7Be(n,p) reactions

The resonance peaks in cross-sections, related to the energy levels of compound nucleus, were believed to be one of the most significant features of the 6Li([Formula: see text]), 3He([Formula: see text]) and 7Be([Formula: see text]) reactions. To explain the cross-sections with resonance peaks, the improved knockout model, which had been successfully applied to study the 6Li([Formula: see text]) reaction in our previous work, was further employed to analyze the 3He([Formula: see text]) and 7Be([Formula: see text]) reactions. The effective excited energy formula, which can explain correlation between resonance peak and energy levels of the compound nucleus for the 6Li([Formula: see text]) reaction, was extrapolated to the 3He([Formula: see text]) and 7Be([Formula: see text]) reactions. A more general form of the effective excited energy formula was proposed. The calculated angle-integrated cross-sections of the 3He([Formula: see text]) and 7Be([Formula: see text]) reactions agreed well with the experimental data. By combining our previous study on the 6Li([Formula: see text]) reaction, the effects of energy levels of the compound nucleus on particle emission for these three reactions were reasonably illustrated.

Neutronics Analyses of the Radiation Field at the Accelerator-Based Neutron Source of Nagoya University for the BNCT Study

The Nagoya University Accelerator-driven Neutron Source (NUANS) is an accelerator-based neutron source by 7Li(p,n)7Be reaction with a 2.8 MeV proton beam up to 15 mA. The fast neutrons are moderated and shaped to beam with a Beam Shaping Assembly (BSA). NUANS is aiming at the basic study of the Boron Neutron Capture Therapy (BNCT) such as an in vitro cell-based irradiation experiment using a water phantom. Moreover, the BSA is developed as a prototype of one for human treatment. We have evaluated the radiation field of NUANS by a Monte Carlo code PHITS. It is confirmed that the radiation characteristics at the BNCT outlet meet the requirement of IAEA TECDOC-1223. Additionally, the radiation field in the water phantom located just in front of the BSA outlet is calculated. In the in vitro irradiation experiment, the boron dose of 30 Gy-eq, which is the dose to kill tumor cells, is expected for 20 min of irradiation at the beam current of 15 mA.

Radiation field characterization with emphasis on the collimator configuration at the compact neutron source RANS-II facility

ABSTRACT The RIKEN Accelerator-driven compact Neutron Source-II (RANS-II) based on the 7Li(p,n)7Be reaction with 2.49 MeV proton injection was installed in a small area of the experimental hall, where the scattered radiation is expected to strongly influence experiments. Therefore, we have begun to study the radiation characteristics of the RANS-II hall by simulation with the Particle and Heavy Ion Transport code System (PHITS) and by experiments to clearly identify the scattered component. In addition, to suppress the background, a collimator is studied with respect to its size, shape, and materials. With the use of the 30 mm borated polyethylene collimator, we found that the background becomes less than 1 of the extracted neutron beam intensity 1.0 m from the Li target. For the experiment, neutron suppression was characterized by measuring the neutron dose rate with a neutron dosimeter and a collimator. The suppression ability of the neutron beam was confirmed by comparing the results of simulations with those of experiments.

Performing Bayesian Analyses With AZURE2 Using BRICK: An Application to the 7Be System

Phenomenological R-matrix has been a standard framework for the evaluation of resolved resonance cross section data in nuclear physics for many years. It is a powerful method for comparing different types of experimental nuclear data and combining the results of many different experimental measurements in order to gain a better estimation of the true underlying cross sections. Yet a practical challenge has always been the estimation of the uncertainty on both the cross sections at the energies of interest and the fit parameters, which can take the form of standard level parameters. Frequentist (χ2-based) estimation has been the norm. In this work, a Markov Chain Monte Carlo sampler, emcee, has been implemented for the R-matrix code AZURE2, creating the Bayesian R-matrix Inference Code Kit (BRICK). Bayesian uncertainty estimation has then been carried out for a simultaneous R-matrix fit of the 3He (α,γ)7Be and 3He (α,α)3He reactions in order to gain further insight into the fitting of capture and scattering data. Both data sets constrain the values of the bound state α-particle asymptotic normalization coefficients in 7Be. The analysis highlights the need for low-energy scattering data with well-documented uncertainty information and shows how misleading results can be obtained in its absence.

The polysiloxane-based scintillator for measurements of fast neutron spectra in nuclear physics experiments

Next generation radioactive ion beam (RIB) facilities among which the SPES facility in construction at INFN-LNL require selective detection apparatuses of high resolution and efficiency as well as high granularity and then the highest covering of the solid angle. On this line the fast neutron detection still represents an uneasy task. Among the organic scintillators, the new polysiloxane-based scintillators have appealing features for measurements of neutron spectra in RIBs applications. In this work a prototype of polysiloxane-based scintillator was fully tested to gamma, alfa and neutron radiation. The scintillator calibration was studied by comparing more than one method and the pulse shape discrimination capabilities were appropriately assessed. Three fast neutron spectra were produced at the INFN-LSN tandem accelerator by means of the 7Li(p,n)7Be reaction at different energies of the incident protons. The measurements of the produced neutron yield together with theoretical estimations based on FLUKA simulations allowed first measurements of the detection efficiency. The fast response, non-toxicity, non-flammability, cheapness and high radiation resistance together with good efficiency and pulse shape capabilities make these scintillators an interesting detector for fast neutron spectroscopy in applications with RIBs.

Collective acceleration of deuterons from the residual chamber atmosphere in a Luce diode

The collective acceleration of deuterons from the residual atmosphere of the Luce diode chamber is studied at a pressure of gaseous deuterium in the range of 0.029–0.177 Pa. The energy and number of accelerated deuterons were determined by neutron time-of-flight spectrometry and by measuring the activity of 13N and 11C radionuclides induced in B4C targets by the reactions 12C(d,n)13N and 10B(d,n)11C, the activity of the 7Be induced by the 10B(p,αγ)7Be reaction was used to control the number of accelerated protons. The neutron time-of-flight shows that the gaseous products of polyethylene anode erosion have no noticeable effect on the energy and number of deuterons accelerated in shots following the first shot of the series. It is shown that the energy of deuterons accelerated from the residual atmosphere is the same as during their acceleration from the near-anode plasma using a deuterated polyethylene anode, but the number of accelerated deuterons per shot depends on the deuterium pressure exponentially, still it is by an order of magnitude smaller even at a pressure of 0.177 Pa. The exponential growth is due to the fact that the number of accelerated deuterons strongly depends on the diode current, which increases noticeably with increasing the deuterium pressure.

Target dependence of isotopic cross sections in the spallation reactions 238U + p, d and 9Be at 1 AGeV * *Supported by the National Natural Science Foundation of China (11875328, 12075327)

The spallation of 238U is an important way to produce rare isotopes. This work aims at studying the cross sections of isotopes produced in 238U + p, d and 9Be reactions at 1 A GeV and their target dependence. (1) A physical model dependent (Bayesian neural network) BNN, which includes the details of IQMD-GEMINI++ model and BNN, was developed for a more accurate evaluation of production cross sections. The isospin-dependent quantum molecular dynamics (IQMD) model is used to study the non-equilibrium thermalization of the 238U nuclei and fragmentation of the hot system. The subsequent decay of the pre-fragments is simulated by the GEMINI++ model. The BNN algorithm is used to improve the prediction accuracy after learning the residual error between experimental data and calculations by the IQMD-GEMINI++ model. It is shown that the IQMD-GEMINI++ model can reproduce the available experimental data (3282 points) within 1.5 orders of magnitude. After being fine tuned by the BNN algorithm, the deviation between calculations and experimental data were reduced to within 0.4 order of magnitude. (2) Based on the predictions by the IQMD-GEMINI++-BNN framework, the target dependence of isotopic cross sections was studied. The cross sections to produce the rare isotopes by the 238U + p, d and 9Be reactions at 1 A GeV are compared. For the generation of neutron-rich fission products, the cross sections for the 238U + 9Be are the largest. For the generation of neutron-deficient nuclei in the region of A = 200–220, the cross sections for 238U + p reaction are the largest. Considering the largest cross sections and the atomic density, the beryllium target is recommended to produce the neutron-rich fission products by the 238U beam at 1 A GeV, while the liquid-hydrogen target is suggested to produce the neutron-deficient nuclei in the region of A = 200–220.

Investigation of the B10(p,α)Be7 reaction from 0.8 to 2.0 MeV

Background: A multitude of broad interfering resonances characterize the B10(p,α)Be7 cross section at low energies. The complexity of the reaction mechanism, as well as conflicting experimental measurements, have so far prevented a reliable prediction of the cross section over the energy ranges pertinent for a boron-proton fusion reactor environment. Purpose: To improve the evaluated cross section of the B10(p,α)Be7 reaction, this study targets the proton energy region from 0.8 to 2.0 MeV, where kinematic overlap of the scattered protons and reaction α particles have made past measurements very challenging. Method: New detailed studies of the reaction have been performed at the Edwards Accelerator Laboratory at Ohio University and the Nuclear Science Laboratory at the University of Notre Dame using time-of-flight and degrader foil techniques, respectively. Results: Proton and α-particle signals were clearly resolved using both techniques, and 16 point differential cross sections were measured over an angular range of θlab=45∘ and 157.5∘. A comprehensive R-matrix analysis of the experimental data, including data from previous low-energy studies of the B10(p,α)Be7, B10(p,p)B10, and B10(p,γ)C11 reactions, was achieved over the region of measurement. Using a representative set of previous data, the fit was extended to very low energies. Conclusions: On the basis of this data and R-matrix analysis, a more reliable and consistent description of the B10(p,α)Be7 cross section has been established. The uncertainty over the energy range of this study has been reduced from ≈20% to ≈10%, and the level structure over this region has been clarified considerably.8 MoreReceived 18 January 2022Accepted 26 April 2022DOI:https://doi.org/10.1103/PhysRevC.105.055802©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDirect reactionsNuclear astrophysicsNuclear fusionNuclear powerNuclear reactionsNuclear reactorsNuclear structure & decaysRadiative captureResonance reactionsProperties6 ≤ A ≤ 19Nuclear PhysicsPlasma Physics

Characterization and description of a spectrum unfolding method for the CATRiNA neutron detector array

The CATRiNA deuterated neutron detector array at Florida State University consists of 16 2″×2″ and 16 4″×2″ EJ-315 detectors with characteristic light output and pulse-shape discrimination capabilities. The unique properties of the detectors, in part due to the anisotropic nature of (d,n) scattering, are used to extract the energy of neutrons via pulse-height spectrum unfolding. The unfolding method uses the light output and response matrix of the detectors to extract neutron energies, independent of the traditional time-of-flight (ToF) technique. Detailed response matrices of the CATRiNA detectors were measured at the Edwards Accelerator Laboratory at Ohio University via the 9Be(d,n) and 27Al(d,n) reactions. Full characterization of the detectors using digital electronics, as well as a description of the unfolding method are reported.

The controversy 3/2+ state in 7Be and its effect on the 3He(α,γ)7Be reaction

The 3He(α,γ)7Be reaction is important for the solar hydrogen burning and the Big Bang Nucleosynthesis. The cross sections at astrophysical energies have not yet been precisely determined, the extrapolation has to rely on the full excitation spectrum of 7Be. A controversy 3/2+ resonance state firstly reported in the study of the 6Li(p,γ)7Be reaction has attracted many attentions in the recent years. In this work, both reactions of 3He(α,γ)7Be and 6Li(p,γ)7Be are reanalyzed together in the formalism of R-matrix with and without the 3/2+ state in 7Be. The results show that this nonnormal state cannot be ruled out based on existing data. According to the present analysis, the 3/2+ resonance does not have a significant impact on the 3He(α,γ)7Be reaction at astrophysical energies, but the accurate measurement of the cross sections of 3He(α,γ)7Be at Ecm > 4 MeV can be used as a verification for the existence of the state.

Features of accelerator-based neutron source for boron neutron capture therapy calculated by particle and heavy ion transport code system (PHITS)

Accelerator-based neutron sources have been developed and installed in recent decades for boron neutron capture therapy (BNCT) in several clinical facilities. Lithium is one of the targets that can produce epithermal neutrons from the 7Li(p,n)7Be near-threshold reaction, and accelerator-based BNCT systems employing a Li target are promising for cancer treatment. The accurate evaluation of the characteristics of an accelerator-based neutron source is a key to estimating the therapeutic effects of the accelerator-based BNCT. Particle and Heavy Ion Transport code System (PHITS) is a general-purpose Monte Carlo code, which can simulate a variety of diverse particle types and nuclear reactions. The latest PHITS code enables simulating the generation of neutrons from the 7Li(p,n)7Be reactions by using the Japanese Evaluated Nuclear Data Library 4.0 high-energy file. Thus, the PHITS code can be adopted for dose estimation during treatment planning for the accelerator-based BNCT. In this study, we evaluated the neutron fluence using the PHITS code by comparing it to reference data. The subsequent neutron transport simulations were performed to evaluate the boron trifluoride detector responses and the recoiled proton fluence detected by a CR-39 plastic detector. These comparative studies confirmed that the PHITS code can accurately simulate neutrons generated from an accelerator using a Li target. The PHITS code has a significant potential for a detailed evaluation of neutron fields and for predicting the therapeutic effects of the accelerator-based BNCT.

Investigation of Dose Rate Distribution in an Experimental Hall of a RIKEN Accelerator-Driven Compact Neutron Source Based on the ⁹Be(p, n) Reaction With 7 MeV Proton Injection

To characterize the dose rate distribution in an experimental hall of a RIKEN accelerator-driven compact neutron source (RANS) based on the ⁹Be(p, n) reaction with 7 MeV proton injection, systematical measurements and calculations for neutron and gamma-ray dose rates by GEometry ANd Tracking (GEANT), Particle and Heavy Ion Transport code System (PHITS), and Monte Carlo N-Particle (MCNP) codes were performed. Calculations always underestimated measurements when proton beam loss effect was not considered. Relatively good agreements were observed among the different simulation codes. To explain the underestimations, the additional dominant neutron and gamma-ray sources due to proton beam loss were identified at the position around exit of the drift tube linac (DTL), made of copper, and the beam pipe from quadrupole (Q) magnets to steering (ST) magnets, made of aluminum, from measurements with placing collimators along linac. The beam loss fractions of 2&#x0025;&#x2013;3&#x0025; on copper and 1&#x0025; on aluminum, respectively, were the most appropriate estimation. In addition, we proposed the possible measures to reduce the measured total dose rate of <inline-formula> <tex-math notation="LaTeX">$3.8~\mu $ </tex-math></inline-formula>Sv/h at the operator position in the control room, with the addition of a wall at the entrance of experimental hall and extension of borated polyethylene (BPE) at the end of the beam. As a result, the dose rate became 2.5 times lower than the current one.

Underground measurement at LUNA found no evidence for a low-energy resonance in the 6Li(p, γ)7Be reaction

The 6Li(p,γ)7Be reaction is involved in all three main nucleosynthesis scenarios: Big Bang Nucleosynthesis, the interaction of cosmic rays with interstellar matter, and stellar nucleosynthesis. Conflicting experimental results have been reported in literature for the 6Li(p,γ)7Be reaction cross section trend at astrophysical energies. A recent direct measurement found a resonance-like structure at Ec.m. = 195 keV, corresponding to an excited state at Ex ~ 5800 keV in 7Be which, however, has not been confirmed by either theoretical calculations or other direct measurements. In order to clarify the existence of this resonance, a new experiment was performed at the Laboratory for Underground Nuclear Astrophysics, located deep underground at Laboratori Nazionali del Gran Sasso (Italy). The 6Li(p,γ)7Be cross section was measured in the energy range Ec.m. = 60-350 keV with unprecedented sensitivity and no evidence for the alleged resonance was found.

3He(α,γ)7Be cross section measurement around7Be known energy levels

The3He(α,γ)7Be reaction plays an important role in two astrophysical scenarios. It is a key reaction in lithium production during the Big Bang Nucleosynthesis and one of the central reaction in the p-p chain in stars. In the case of the former event, the Gamow energy of the reaction is around 0.2 MeV, while in the case of the p-p chain in the Sun, an order of magnitude less, around 0.023 MeV. Experimental investigation at such low energies is very difficult, if possible at all, thus low energy extrapolation inevitable to predict the reaction rate at these energies. The extrapolation and its uncertainty are influenced by the precision and covered energy range of the data used. There are many precision datasets between Ec.m.= 0.3–3.1 MeV, but only one below and one above. At higher energies known levels of7Be exist, which motivates the study of that energy range. Therefore, we performed investigations in the energy range of Ec.m.= 4.3–8.3 MeV, where the radiative cross section has not been studied so far. For the cross section determination, the activation technique was used utilising a thin-windowed gas cell and the MGC-20 cyclotron of ATOMKI.

Neutron yield calculation of p-Li thick target by using PHITS with JENDL-4.0/HE and ENDF/B-VII for BNCT application

ABSTRACT The lithium thick target bombed with low-energy protons is one of the promising neutron sources for the Boron Neutron Capture Therapy (BNCT). The benchmark calculations of the neutron Thick Target Yield (TTY) of the lithium target are conducted by the Particle and Heavy Ion Transport Code System PHITS with ACE formatted files of JENDL-4.0/HE and ENDF/B-VII and the DROSG-2000 code for the incident proton energy of around 3 MeV. Also, neutron TTY of the lithium thick target with a titanium window is evaluated for the Nagoya University Accelerator-driven Neutron Source (NUANS). Finally, the TTY evaluated with PHITS is applied for the neuron transport calculation for the Beam Shaping Assembly (BSA) of NUANS. As a conclusion, it is considered that ENDF/B-VII is more feasible than JENDL-4.0/HE for the 7Li(p,n)7Be reaction around 3 MeV of the proton energy.

Evaluating the dependency of neutron spectra and absorbed dose rates on the collimation field size in fast neutron therapy

The aim of this research was to investigate the relationship between the collimator aperture and fast-neutron flux, neutron-energy spectrum and absorbed dose rate. For remote therapy, rather large fluxes of fast neutrons are needed which can create dose levels in the tissues of at least 0.1 Gy/min with a source-patient distance of 1 m. Advantageously for these purposes, the 9Be(d, n) reaction was investigated with deuteron energy of 13.6 MeV. The mean energy of the outgoing neutrons was obtained using the code PACE 4 (LISE++) which gave the value of about 5.2 MeV. The maximum neutron flux was at an energy of about 2.5 MeV. Samples activation analysis was deployed to measure the neutron flux in the energy-region [0–14 MeV]. The experimental works were carried out using Al, Fe, Cu and Cd foils which installed on the collimator apertures. To investigate the neutron spectrum, fluxes, and dose rates absorbed at the position of patients, experiments were conducted for four different neutron irradiation-field sizes, which can be modified by the removable-polyethylene parts. Simulation results obtained by the code MCNP-4C and PACE4 (LISE++) were comparable with the experimental data to some extent with consideration of some uncertainties of PACE4 results. It can be concluded that the neutron flux is depended on the irradiation-field size where the neutron flux output for bigger aperture size was about +25% comparing with the smaller ones. These results could play a significant role in improving the neutron flux and optimizing the collimation system utilized in fast neutron therapy. In addition, this can lead to optimization of irradiation canals installed in the nuclear reactors which employed for production of medical isotopes, material testing and many other applications.