Compact Accelerator-driven Neutron Source Research Articles

Development of a neutron generating target for compact neutron sources using low energy proton beams

A neutron generating target using a Be(p,n) reaction was developed for a RIKEN compact accelerator-driven neutron source (RANS). The major problem of targets using a low energy proton beam is blistering, which is actually due to hydrogen embrittlement caused by injected hydrogen. To avoid this problem, the authors have proposed a new target design with a hydrogen diffusible backing and its design was modeled using finite-element analysis (FEM) and Monte-Carlo ion injection simulation. Also, the mechanical strength and heat removal capability of the target were considered by FEM. Based on those simulations, a new target was manufactured and applied to RANS and operated for 1 year without any problems. Also, the residual radioactivity of the target was investigated by experiment and simulation.

The Fourth Meeting of the Union for Compact Accelerator-Driven Neutron Sources (UCANS)

About 65 scientists, engineers, and research students from 15 countries attended the UCANS-V Meeting in Padova, Italy, May 12–15, 2015, which was hosted jointly by the INFN Laboratori Nazionali di ...

Applications of Compact Accelerator-driven Neutron Sources: An Updated Assessment from the Perspective of Materials Research in Italy

In 2005 the International Atomic Energy Agency (IAEA) in Vienna published a report [1] on ‘Development Opportunities of Small and Medium Scale Accelerator Driven Neutron Sources’ which summarized the prospect of smaller sources in supporting the large spallation neutron sources for materials characterization and instrumentation, a theme advocated by Bauer, Clausen, Mank, and Mulhauser in previous publications [2–4]. In 2010 the Union for Compact Accelerator-driven Neutron Sources (UCANS) was established [5], galvanizing cross-disciplinary collaborations on new source and neutronics development and expanded applications based on both slow-neutron scattering and other neutron-matter interactions of neutron energies ranging from 10-6 to 102 MeV [6]. Here, we first cover the recent development of ongoing and prospective projects of compact accelerator-driven neutron sources (CANS) but concentrate on prospective accelerators currently proposed in Italy. Two active R&D topics, irradiation effects on electronics and cultural heritage studies, are chosen to illustrate the impact of state-of-the-art CANS on these programs with respect to the characteristics and complementarity of the accelerator and neutronics systems as well as instrumentation development.

Design of Neutron Reflectometer in the Angle-resolved Dispersive Mode for Compact Accelerator Based Neutron Sources

Compact accelerator-driven neutron sources take advantage of their readiness of operation and high adaptability to various experiments, although their neutron flux is low. We are now working on installing a reflectometer to Kyoto University Accelerator based Neutron Source (KUANS). Neutron reflectometer (NR) is one of the most simple but powerful spectrometer, in which neutron reflectivity from the surface of a sample is measured and analyzed to give so called ‘depth profile’ of the sample, which represents the distribution of materials along the surface normal direction. Usually, reflectometer requires narrow well-collimated beam. For the present reflectometer, however, incident neutron beam is narrowed at the sample position but not so much collimated to allow variety of incident angle to the sample simultaneously assuming the specular reflection at the sample surface. This multi-incident angle measurement helps to compensate weak intensity of KUANS. The motivation of this study is development of the NR with the readiness of operation for a preliminary experiment. In this study, the design of the NR is presented and the reflectivity is estimated via Monte-Carlo simulation. It was found that measurable lowest reflectivity is down to 10-2.

Preliminary Experiments of Coded Source Neutron Imaging on Accelerator-driven Neutron Source

Coded source imaging is a possible technique to improve the quality of neutron imaging based on compact neutron sources. Experiments of coded source imaging were carried out on PKUNIFTY. It is the first time that coded source neutron imaging is applied on a compact accelerator-driven neutron source. In order to meet the requirements of coded source neutron imaging, the moderator was tried to be modified to deliver an evener neutron beam. The preliminary experimental results were successfully reconstructed with wiener filter deconvolution and Lucy-Richardson maximum likelihood iteration algorithm. The reconstructed results are not good enough in these experiments due to the low neutron fluence and the epithermal neutron interference. The numerical simulation shows that it could be improved by increasing the neutron fluence.

Neutron Yields of Thick Be Target Bombarded with Low Energy Deuterons

Utilization of the 9Be(d,n) reaction is an important option for compact accelerator-driven neutron sources, especially for low energy accelerators. It is suitable for small scale thermal or cold neutron sources. However the existing neutron yield data of the Be(d,n) reaction show large discrepancies in the low energy range. We have measured the neutron yields from thick Be target bombarded with 0.2 – 3 MeV deuterons at PKU. Here we compared our results with those from other authors. In general, Kononov's data show the best agreement with ours. We present the total and the forward-direction neutron yields in terms of empirical formulas obtained from satisfactory fits of our data.

Preliminary Experiment of Magnetic Imaging Using Polarized Pulsed Neutrons at HUNS

Imaging using polarized neutrons is one of the most attractive techniques in the neutron imaging field, because of its capability to visualize magnetic field inside materials or spaces by analyzing neutron polarization. An advanced method, which can quantify the magnetic field by combining the time-of-flight method with a polarization analysis of pulsed neutrons, has been developed at J-PARC. To introduce this method to the compact accelerator-driven neutron source, we have started the magnetic imaging experiments at Hokkaido University Neutron Source (HUNS). Using an experimental system consisting of a pair of magnetic super-mirrors as a polarizer and an analyzer, a spin flipper, and a two-dimensional neutron detector, we obtained the polarization of 90% at the wavelength over 6Å. The first demonstration experiments were performed for coil samples. As a result, an oscillatory behaviour of polarization depending on the wavelength due to the neutron spin's Larmor precession was clearly observed.

Design of Moderator of a Compact Accelerator-driven Neutron Source for Coded Source Imaging

Coded source imaging (CSI) is a possible method to solve the contradiction between neutron flux and L/D ratio. Peking University neutron imaging facility (PKUNIFTY) is a RFQ accelerator based facility. The CSI experiments were carried out on PKUNFTY to test the benefits that this technique might bring. The CSI technique gets more restricts on the moderator, especially the neutron distribution in the inner collimator, where the coded mask sampling the source. The effect caused by the non-uniformity of neutron distribution on the mask plane was investigated. The slope type non-uniformity should less than 20% to keep the artifact in the reconstructed image insignificant. The PKUNIFTY moderator was modified according to the above limit. The preliminary experiments shown the moderator design for coded source imaging is acceptable.

The replacement of research reactors with a compact proton linac for neutron radiography

The work presented here examines a neutron radiography facility, based on accelerator-driven compact neutron source, in order to find a suitable replacement for the facilities, which is based on research nuclear reactors. High-quality neutrons beam can be produced via the 9Be(p,n)9B reaction at proton energies of about 4MeV. Except for the Be target the materials considered were compatible with the European Union Directive on ‘Restriction of Hazardous Substances’ (RoHS) 2002/95/EC. According to this directive some common materials in radiography units such as lead and cadmium have been excluded. The suggested facility has been simulated with an extensive range of parameters, which characterizes the neutron radiography, and the results specify that an accelerator-based neutron source is an attractive alternative to research nuclear reactors.

The Third Meeting of the Union for Compact Accelerator-driven Neutron Sources

The Third Meeting of the Union for Compact Accelerator-driven Neutron Sources

Simulation calculations of transmissions for neutron total cross-section measurements of MAs and LLFPs by complementary use of a compact accelerator-driven neutron source

We performed simulation calculations of neutron transmission spectra for minor actinide and long-lived fission product samples with pulsed neutron beams produced by the two neutron sources: the Accurate Neutron-Nucleus Reaction measurement Instrument (ANNRI) at the Japan Spallation Neutron Source (JSNS) that provides the world's most intense pulsed neutron beam, and a compact accelerator-driven neutron source. For the both cases, we assumed to put a neutron detector at downstream of the sample and took into account the detector efficiency of neutrons to estimate statistics. ANNRI gives high statistical neutron transmission spectra. Therefore, it is useful for obtaining the total cross-section data through the transmission spectra for the small amount sample or the small cross-section regions between the resonances not only for monitoring the beam condition during the neutron capture-reaction measurements at ANNRI. On the other hand, a compact neutron source shows transmission spectra at resonances with less deformation by its single bunch beam. This implies that the compact neutron source is useful for assigning the resonances and the resonance analysis.

Design of RFQ Accelerator Facility of PKUNIFTY

Abstract The Peking University Neutron Imaging Facility (PKUNIFTY) is being constructed, which is a compact acceleratordriven neutron source. The accelerator is a radio frequency quadrupole (RFQ) accelerator, which can deliver a 2 MeV deuteron beam. The neutrons are generated by deuterons bombarding beryllium target. The accelerator facility mainly consists of ECR (electron cyclotron resonance) ion source, LEBT (low energy beam transportation), RFQ cavity, HEBT (high energy beam transportation), RF transmitter and control system. This paper will introduce the requirements and design of that accelerator facility.

Union of Compact Accelerator-Driven Neutron Sources (UCANS) II Design activities for the Beam Dump of ESS Bilbao

ESS Bilbao facilities will require a Beam Dump to stop their proton beam during certain operation phases. The basic design concept of ESS Bilbao Beam Dump consists of a metal conical cavity with helical cooling channels. It has to be able to withstand the particular conditions caused by radiation and energy deposition from the proton beam. In the process of designing the Beam Dump, the Group of Target and Neutronic Applications of ESS Bilbao is aiming for an analysis that integrates protonics, thermal hydraulics and mechanics. By means of combining different software tools, the Group is expecting to obtain a design that is optimized from the point of view of every discipline.

Neutron radiography with compact accelerator at Peking University: Problems and solutions

Abstract The better contrast sensitivity and resolution of neutron radiographs require higher neutron flux and enough L/D . The neutron yield of compact accelerator-driven neutron sources is usually lower than reactor and spallation neutron sources. It is difficult to obtain the high L/D and the high neutron flux simultaneously. The deuteron beam and Be target were selected for Peking University neutron imaging facility (PKUNIFTY), which can give higher neutron yield at lower beam energy. That means smaller facility size and lower power consumption in the accelerator, and therefore the lower cost. But that reaction also gives higher yield, so how to realize higher n/ratio is another issue. For intense deuteron beam the deuterons lost in the structure materials may become target atoms and generate neutrons under the bombardment of the succeeded beam. This paper will discuss the above problems, and introduce the PKUNIFTY design, which tried to reach a compromise among the various conflicting demands and meet the basic requirements of neutron radiography.

PKUNIFTY: A neutron imaging facility based on an RFQ accelerator

Abstract A neutron imaging facility, PKUNIFTY, based on a radio frequency quadrupole (RFQ) accelerator-driven compact neutron source, presently under construction at the Peking University, is described. It consists of a deuteron linear accelerator, a neutron target–moderator–reflector assembly, and a thermal neutron imaging system. Neutrons are generated via the deuteron–beryllium reaction with an expected fast-neutron yield of 3×10 12 n/s. The thermal neutron flux on the imaging plane is 5×10 5 n/cm 2 /s at a nominal L/D ratio of 50, and the L / D ratio can be selectable over a range of 25–200. The corresponding n/γ ratio is close to or higher than 1×10 10 n/cm 2 /Sv. The field of view is 20 cm×20 cm at 2 m downstream of the collimator entrance aperture where the thermal neutron flux uniformity is better than 7%. The effective Cd ratio can be tuned by using a light chopper and neutron time-of-flight technique without excessive sacrifice of the thermal neutron flux.

Design of RFQ accelerator facility of PKUNIFTY

The Peking University Neutron Imaging Facility (PKUNIFTY) is being constructed, which is a compact accelerator-driven neutron source. The accelerator is a radio frequency quadrupole (RFQ) accelerator, which can deliver a 2 MeV deuteron beam. The neutrons are generated by deuterons bombarding beryllium target. The accelerator facility mainly consists of ECR (electron cyclotron resonance) ion source, LEBT (low energy beam transportation), RFQ cavity, HEBT (high energy beam transportation), RF transmitter and control system. This paper will introduce the requirements and design of that accelerator facility.

Conceptual study of a compact accelerator-driven neutron source for radioisotope production, boron neutron capture therapy and fast neutron therapy

The feasibility of a compact accelerator-driven device for the generation of neutron spectra suitable for isotope production by neutron capture, boron neutron capture therapy and fast neutron therapy, is analyzed by Monte Carlo simulations. The device is essentially an extension of the activator proposed by Rubbia [CERN/LHC/97-04(EET)], in which fast neutrons are diffused and moderated within a properly sized lead block. It is shown that by suitable design of the lead block, as well as of additional elements of moderating and shielding materials, one can generate and exploit neutron fluxes with the spectral features required for the above applications. The linear dimensions of the diffusing–moderating device can be limited to about 1 m . A full-scale device for all the above applications would require a fast neutron source of about 10 14 s −1 , which could be produced by a 1 mA , 30 MeV proton beam impinging on a Be target. The concept could be tested at the Frascati Neutron Generator, a source producing 14 MeV DT fusion neutrons at the rate of 10 11 s −1 and located in a large shielded room.