Compact Accelerator-driven Neutron Source Research Articles

Design and beam dynamics simulation of an 8 MeV compact accelerator-driven neutron source

A compact accelerator-driven neutron source is proposed at Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, called Sun Yat-Sen University Proton Accelerator Facility (SYSU-PAFA). The proton accelerator is composed of a proton electron cyclotron resonance source, a four-vane radio frequency quadrupole (RFQ), and an alternative phase focusing drift tube linac (APF-DTL). It can accelerate 10 mA proton beam to 8 MeV. Due to the high current, beam matching is particularly important. In order to achieve beam matching between various components, beam transport sections are needed. The beam transport line is divided into three segments. The Low Energy Beam Transport (LEBT) ensures that the beam parameters are matched before entering the RFQ. The Medium Energy Beam Transport (MEBT) segment efficiently transfers the beam between the RFQ and DTL. The High Energy Beam Transport (HEBT) focuses on transporting the beam to the targets. The design goal of beam transport line is as short as possible while ensuring high efficiency of beam transportation. SYSU-PAFA has an overall transmission efficiency of 99%, with optimal transverse matching conditions between beam transport and RFQ or DTL accelerators. The efficient use of solenoids and magnets allows for a compact transmission section, resulting in a total length of 13.6 meters, shorter than most accelerators at the same beam energy. This paper will provide the detailed beam dynamics of the compact accelerator.

A compact accelerator driven neutron source at the Applied Nuclear Physics Laboratory, Lund University

The Applied Nuclear Physics Group at Lund University has constructed a CANS (Compact Accelerator-driven Neutron Source). The CANS is based around a 3 MV, single-ended, Pelletron accelerator, which is used to impinge a 2.8 MeV deuterium beam into a beryllium target. The anticipated neutron production will be on the order of 1010 n/s in 4π sr, with future upgrades expected to increase neutron production to 1011 n/s. Neutron energy will be up to 9 MeV with peak emission at ∼5 MeV. Shielding and moderation will be provided by a large water tank surrounding the target, with exit ports to allow moderated neutrons to be directed to experiments. The thermal-neutron flux at the exit of the extraction ports is anticipated to be up to 106 n/cm2/s. The CANS will be used to forward the activities of the group in the area of neutron-activation analysis, in addition to a broader range of neutron related applications.

Resolution analysis of thermal neutron radiography based on accelerator-driven compact neutron source

Resolution analysis of thermal neutron radiography based on accelerator-driven compact neutron source

Pseudo-random time modulation technique for neutron diffraction instruments on compact accelerator-driven neutron sources

Time modulation methods are routinely used on neutron scattering time-of-flight instruments, which exploit the time structure of neutron pulses for energy determination. In the past, complex time modulation methods were proposed, either to maximize the neutron flux which can be used, or to increase the energy resolution of the measurements. In this article, we explore the possibilities offered by such methods and in particular random modulation using statistical choppers to improve the performances of the DIoGENE scattering instrument installed around the IPHI-neutron CANS source at Saclay. We conclude that when the source is operated in continuous mode, the implementation of a statistical chopper is very efficient to perform either metallurgical studies such as strain scanning or phase transition studies. Random modulation techniques may be easily and efficiently implemented because the high capacity of modern computers enables high-speed data processing from large surface pixelated detectors.

Effects of neutron radiation as cosmic radiation on food resources

One of the major challenges in deep space exploration are effects of cosmic rays on human body and soft error, but equally important are their effects on food resources. In this study, we focused on neutrons as the secondary particle in the deep space environment and investigated how they affect food resources. Fast neutron was irradiated by the RIKEN Accelerator-driven compact Neutron Source (RANS) on meat sample. Biochemical analysis was conducted to present concrete effects of cosmic rays on food in deep space environment. Oxidative and nitrative modifications of proteins were detected by the electrophoresis and Western blotting. The result shows that nitrative modification of tryptophan, which is an essential amino acid in protein, tended to increase with increasing neutron dose.

Development of a Pelletron-based compact neutron source

The Applied Nuclear Physics Group at Lund University is constructing a prototype CANS (Compact Accelerator-driven Neutron Source). The CANS is based around a 3 MV, single-ended, Pelletron accelerator, which is used to impinge a 2.8 MeV deuterium beam into a beryllium target. The anticipated neutron production will be on the order of 1010 n/s in 4π sr. A further upgrade to the ion source of the Pelletron is expected to increase neutron production to 1011 n/s. Neutron energies will be up to 9 MeV with peak emission at ∼5 MeV. Shielding and moderation will be provided by a large water tank surrounding the target, with three exit ports to allow neutrons of different energies to be directed to experiments. The design is supported by simulation results which predict fast-neutron fluxes of 9×104 to 5×106 n/cm2/s, and thermal-neutron fluxes of 1×104 to 5×104 n/cm2/s to be readily obtainable with a 10 µA deuteron beam.

Simulation and design of an IPHI-based neutron source, first steps toward SONATE

Facilities providing bright thermal neutron beams are of primary importance for various research topics. At CEA-Saclay, a compact accelerator driven neutron source, SONATE, is investigated in taking advantage of the IPHI accelerator able to deliver a 3 MeV proton beam with an intensity up to 100 mA. To optimize the performances of such a neutron source, it is necessary to maximize the thermal neutron flux while minimizing the contribution of other particles. In this work, optimization has been performed using the Monte Carlo code TOUCANS, a neutron transport code based on Geant4 developed at CEA-Saclay. This latter has been coupled to PROMETHEE, a software allowing multi-objective optimization for many simulation software. In this work the Kriging metamodel based approach is used to optimize a neutron beamdump. To take into account the various constraints, noise on the detection system and radiation protection issues, several beamdump configurations are evaluated. The variation of beamdump parameters makes it possible to identify the set of optimal solutions, the Pareto front. It allows to focus on the set of best choices and to choose wisely the best configurations. After describing the validation of TOUCANS on experimental tests performed from 2016 to 2022, the capability of such an approach will be presented.

Fabrication and RF test of the 500 MHz-RFQ linear accelerator for a transportable neutron source RANS-III

At RIKEN, a transportable accelerator-driven compact neutron source (RANS-III) is under development for an on-site nondestructive inspection of the degradation of old concrete and reinforcing steel. RANS-III consists of an ion source, a low-energy beam transport, a radio frequency quadrupole linear accelerator (RFQ linac), a radio frequency (RF) system, a high-energy beam transport, a target station and a neutron measurement system. Because the inner diameter of the RFQ linac is inversely proportional to the resonance frequency, the resonance frequency of the RANS-III RFQ linac in this study was chosen to be 500 MHz, which is 2.5 times that of the RANS-II RFQ linac. Therefore, the inner diameter and weight of the RANS-III RFQ linac were reduced to approximately half and one third, respectively, of those of the RANS-II RFQ linac. The RANS-III RFQ linac was designed to accelerate a proton beam with a 10 mA peak current and 100 μA average beam current from 30 keV to 2.49 MeV (Journal of Disaster Research 12(3) (2017) 585–592). Based on the evaluations, an RFQ linac for RANS-III was fabricated, and the RF characteristics of the cavity, such as the resonant frequency and electric-field distribution, were measured using a low-power test and tuned using fixed tuners. In addition, RF couplers and RF systems were constructed to inject RF power into the RANS-III RFQ linac, and RF input tests were performed.

The HERMES reflectometer at the JULIC Neutron Platform

HERMES is a time-of-flight reflectometer that operated at the Orphée reactor until 2019. In 2022, HERMES was installed at the JULIC (Jülich Light Ion Cyclotron) Neutron Platform as part of a collaboration between the Laboratoire Léon Brillouin and the Jülich Centre for Neutron Science. The main goal of the current setup is to probe the viability of neutron instrumentation at a High Current Compact Accelerator-driven Neutron Source (HiCANS). As the flux at the JULIC neutron platform is several orders of magnitude lower than the original Orphée flux or the expected flux for a HiCANS, our current objective is to perform reflectivity experiments with supermirrors as a proof of concept. Nevertheless, Monte-Carlo simulations showed that the HERMES instrument’s performance at a HiCANS such as HBS or ICONE could match that of reflectometry instruments operating at research reactors or spallation sources. An experiment with a supermirror carried out in December 2022 allowed us to preliminary prove the feasibility of this kind of experiments at an accelerator-driven neutron source.

New Material Exploration to Enhance Neutron Intensity below Cold Neutrons: Nanosized Graphene Flower Aggregation.

It is proposed that nanosized graphene aggregation could facilitate coherent neutron scattering under particle size conditions similar to nanodiamonds to enhance neutron intensity below cold neutrons. Using the RIKEN accelerator-driven compact neutron source and iMATERIA at J-PARC, we performed neutron measurement experiments, total neutron cross-section and small-angle neutron scattering on nanosized graphene aggregation. For the first time, the measured data revealed that nanosized graphene aggregation increased the total neutron cross-sections and small-angle scattering in the cold neutron energy region. This is most likely due to coherent scattering, resulting in higher neutron intensities, similar to nanodiamonds.

Activation imaging of drugs with hybrid Compton camera: A proof-of-concept study

The visualization of drugs is essential for cancer treatment. Although several methods for visualizing drugs have been proposed, a versatile method that can be easily applied to various drugs has not yet been established. Therefore, we propose “activation imaging,” in which a drug is irradiated with thermal neutrons and becomes radioactive, enabling visualization using emitted x rays and/or gamma rays. Activation imaging does not require the conjugation of specific tracers with drugs. Therefore, it can be easily applied to a variety of drugs, drug carriers (e.g., metal nanoparticles), and contrast agents. In this study, neutron activation, gamma-ray spectroscopy, and imaging of drug carriers, anticancer drug, and contrast agents were performed. Gold nanoparticles (AuNPs) and platinum nanoparticles were used as drug carriers, cisplatin was used as an anticancer drug, and gadoteridol and iohexol were used as contrast agents. As a neutron source, the RIKEN accelerator-driven compact neutron source II (RANS-II) was utilized. The imaging was performed using a hybrid Compton camera (HCC). The HCC can visualize x rays and gamma rays ranging from a few keV to nearly 1 MeV, which enables the imaging of various x rays and gamma rays emitted from the activated drugs. As a result, the gamma-ray spectra indicated the generation of radioisotopes through neutron irradiation, and AuNPs and iohexol were visualized.

The prototyping of a high-resolution neutron activation analysis system – based on a Pelletron accelerator and fast pneumatic sample-transport

A new neutron activation analysis system is currently being designed at Lund University. The design incorporates a compact accelerator driven neutron source, based on a 3 MV Pelletron accelerator and a pneumatic sample conveyor to transport samples from the neutron source to a measurement station consisting of an array of high-purity Ge γ-ray detectors. A prototype for this new station is currently in operation, with a Genie 16 SODERN neutron generator used in place of the compact accelerator driven neutron source. Preliminary results from the prototype system are presented, alongside qualitative analysis supported by simulations performed in FISPACT-II. The system has been tested with the measurements of Al and In foils, using a PLA sample holder. The results demonstrate that activation products with half-lives of as little as 2 s can be measured. γ-rays from the 2 s isomer, 116n In are clearly observed providing the irradiation and measurement times are appropriately chosen.

Absolute [formula omitted]He polarimetry for a double-chambered cell using transmission of thermal neutrons

We present an absolute 3He polarimetry method based on thermal neutron transmission for a double-chambered cell. This method utilizes the fact that a 3He nucleus has a large absorption cross section and a spin dependence for thermal neutrons. The cell had a pumping chamber and a target chamber. Polarized 3He gas was produced in the pumping chamber by SEOP and then diffused into the target chamber. The 3He polarization in the target chamber was determined by comparing the neutron transmissions with the polarized and unpolarized targets. The measurement was performed at the RIKEN Accelerator-Driven Compact Neutron Source. The 3He polarization in the target chamber was determined with a statistical error of 1.8% and systematic uncertainty of 0.6%. This method can be used to obtain high-precision data of spin observables in few-nucleon scattering for the investigation of nuclear forces.

Demonstration of Neutron Phase Imaging Based on Talbot–Lau Interferometer at Compact Neutron Source RANS

Neutron imaging based on a compact Talbot–Lau interferometer was demonstrated using the RIKEN accelerator-driven compact neutron source (RANS). A compact Talbot–Lau interferometer consisting of gadolinium absorption gratings and a silicon phase grating was constructed and connected to the RANS. Because of pulsed thermal neutrons from the RANS and a position-sensitive detector equipped with time-of-flight (TOF) analysis, moiré interference patterns generated using the interferometer were extracted at a TOF range around the design wavelength (2.37 Å) optimal for the interferometer. Differential phase and scattering images of the metal rod samples were obtained through phase-stepping measurements with the interferometer. This demonstrates the feasibility of neutron phase imaging using a compact neutron facility and the potential for flexible and unique applications for nondestructive evaluation.

Improvement of Neutron Diffraction at Compact Accelerator-driven Neutron Source RANS Using Peak Profile Deconvolution and Delayed Neutron Reduction for Stress Measurements

Improvement of Neutron Diffraction at Compact Accelerator-driven Neutron Source RANS Using Peak Profile Deconvolution and Delayed Neutron Reduction for Stress Measurements

Design of the proton injector for compact neutron source DARIA

Project of the proton accelerator-driven compact neutron source DARIA (Dedicated for Academic Research and Industrial Application) is developed in order to replace small and middle flux neutron sources based on the nuclear reactors. DARIA has a uniquely high ratio of efficiency to cost due to deep optimization of each key element of the system (proton injector and accelerator, target, neutron moderator and neutron instruments. A unique ECR ion source, developed at the IAP RAS, would be used as a proton beam injector. In such device the plasma is heated by the powerful 28 GHz gyrotron radiation, providing a record level of volumetric energy input for such systems over 100 W/cm^3. The high plasma density and the optimal electron temperature provide proton beams formation with a current of up to several hundred mA and an emittance that meets the requirements of modern accelerators. The paper discusses the advantages of using such an ion source, its scheme and design performance.

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.

Two Design Options for Compact Linear Accelerators for High Flux Neutron Source

We describe and compare two optimized design options of RF linear accelerators with different resonant frequencies at 162.5 MHz (f0) and 325 MHz (2∙f0). The RFQ + DTL linacs have been designed to provide 13 MeV acceleration to a proton beam for achieving a fast neutron yield of not lower than 1013 n/s via 9Be(p, n)9B reaction in pulsed-mode operation. Our design studies show that none of the two options is better than the other, but that the choice of operating frequency will mainly be determined by the accelerator length and RF cost consideration. This study can serve as a basis for the design of an initial stage of a new high brilliance Compact Accelerator-driven Neutron Source (CANS), aiming to use neutron scattering techniques for studying material properties in fundamental physics, materials science, nuclear energy, as well as for industries and societal challenges.

Improvement of Geant4 Neutron-HP package: From methodology to evaluated nuclear data library

An accurate description of interactions between thermal neutrons (below 4 eV) and materials is key to simulate the transport of neutrons in a wide range of applications such as criticality-safety, reactor physics, compact accelerator-driven neutron sources, radiological shielding or nuclear instrumentation, just to name a few. While the Monte Carlo transport code Geant4 was initially developed to simulate particle physics experiments, its use has spread to neutronics applications, requiring evaluated cross-sections for neutrons and gammas between 0 and 20 MeV (the so-called neutron High Precision – HP – package), as well as a proper offline or on-the-flight treatment of these cross-sections. In this paper we will point out limitations affecting the Geant4 (version 10.07.p01) thermal neutron treatment and associated nuclear data libraries, by using comparisons with the reference Monte Carlo neutron transport code Tripoli-4®, version 11, and we will present the results of various modifications of the Geant4 Neutron-HP package, required to overcome these limitations. Also, in order to broaden the support of nuclear data libraries compatible with Geant4, a nuclear processing tool has been developed (the code is available on a GitLab repository) and validated allowing the use of the code together with ENDF/B-VIII.0 and JEFF-3.3 libraries for example. These changes will be taken into account in an upcoming Geant4 release.

Conceptual design of the grazing-incidence focusing small-angle neutron scattering (gif-SANS) instrument at CPHS

Developing small-angle neutron scattering techniques at compact accelerator-driven neutron sources (CANS) is of great importance for expanding the user community and advancing CANS capability. At the Compact Pulsed Hadron Source (CPHS) at Tsinghua University, neutron-focusing mirrors are under intensive research to address the challenge. A grazing-incidence focusing SANS (gif-SANS) project is initialized. It employs a nested supermirror assembly with a large collecting area to achieve ⩾ 10 5 n/s neutron intensity at Q min ⩽ 0.007 Å − 1 . It will equip two detectors, one being a 3He detector for normal Q-range measurements, and the other being a high-resolution detector for extending the Q min down to 10 − 3 Å − 1 . In this work, we present the conceptual design of the gif-SANS at CPHS. Such a scheme is conducive to enable high-performance SANS measurements at CANS.