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A Frisch-grid Ionization Chamber (FGIC) for the measurement of low activity of alpha-particle emitters has been built. The design and performance are described in this paper. According to the Shockley–Ramo theorem and the experiment, the key parameter grid inefficiency was studied in detail. The experimental and calculated values of the correction factor are shown to be in good agreement. In the measurement of the alpha-activities of a 234,238U sample, the detection efficiency was investigated based on the Monte-Carlo method. Considering this influence, the activity of alpha-particle emitters was identified.

The Jülich Centre for Neutron Science is working on the project to develop, design and demonstrate anaccelerator driven high-brilliance neutron source (HBS) as an efficient and cost-effective alternative tocurrent low- and medium-flux reactor and spallation sources. The HBS comprises a high current protonacceleratorwith an energy of 70 MeV and a beam current of 100 mA, a compact neutron target of 100 kWpower, sophisticated cold and thermal moderator systems and an optimized neutron transport system toprovide thermal and cold neutrons with high brilliance for a full suite of epithermal, thermal and coldinstruments.The project offers construction of a scalable neutron source fora user facility with open access and serviceaccording to the various and changing demand of its communities. Embedded within an internationalcollaboration with partners from Germany, Europe and Japan the Jülich HBS project offers best flexiblesolutions to the scientific and industrial users. The overall conceptual design of HBS was published in arecent report.We will present the current status of the project, progress and next steps regarding accelerator, target,moderators and beam delivery development, milestones and the vision for the realization of such a facility.

The shutdown of several national reactor driven neutron sources has stimulated intense research and development activities for successor facilities[1]. A promising technology is the neutron production by low energy nuclear reactions, that can be driven by accelerators operating in the particle energy range between 3 and 100 MeV. While the neutron yield of theses reactions is much lower than the neutron yield of the spallation reaction, the lower particle energy enables a very close coupling of the thermal and cryogenic moderators to the target and therefore small volume moderators with a high density of slow neutrons. On the other hand, the comparably low particle energies facilitate the shielding issue significantly and allow therefore neutron optical components in a distance as close as 50 cm from the thermal or cold moderator surfaces allowing the extraction of a reasonably divergent beam from the source, which can be efficiently transported to the sample by modern neutron optics. Therefore instruments, which require a large phase space, can benefit strongly from the characteristics of a low energy accelerator driven neutron facility (LENF). Among them are typically spectrometers of both direct and indirect geometry, which require typically relaxed spatial and angular resolution and a good energy resolution. Here we present source parameters that have been determined for different spectrometers employing thermal and cold neutrons.

The design of a compact D–D neutron generator with a neutron yield greater than 1 × 1 0 8 n/s is presented in this paper. A duoplasmatron ion source is used to supply the deuteron beam. Deuterium ions are extracted and accelerated by a single-gap accelerating column and then bombard onto a drive-in molybdenum target where neutrons are produced through D–D fusion reactions. The target is cooled by the circulating deionized water. The extraction-accelerating electrode and the target system are enclosed inside a stainless steel vacuum vessel. The ion source is at ground potential, and the target is biased to a negative potential. The electric field distribution inside the vacuum vessel, the ion beam optic, the thermal analysis of the target and the effect of secondary electron suppression are calculated. And these calculation results are used to optimize and evaluate the designed scheme. Calculation results show that the design of the neutron generator satisfies necessary engineering requirements.

A high-intensity accelerator-based D-D/D-T fusion neutron source (ZF-400) with a thick adsorption target is designed with an intensity of $ 10^{13}$ n/s. A high-current microwave ion source is used to produce a large current deuteron beam, and neutrons are generated by irradiating the deuteron beam on a deuterium-adsorption target or tritium-adsorption target. According to the particle-in-cell (PIC) code, the length of the whole high-current D+ beam transport line is 500cm, the D+ beam transfer efficiency is up to 96%, and various components can match each other. On the rotating target, the D+ beam spot size is about 20.0 mm with energy of 450 keV. Based on the heat conduction theory, the thick adsorption rotating target with water-cooling can withstand the D+ ions beam with 450 kV/50 mA and ensure that the temperature is less than 200 °C. According to the multi-layer computing model, neutron energy spectra, angular distributions and yields for the thick target can be calculated with remarkable precision. The neutron energy spectra are non-mono-energetic neutrons for the ZF-400 neutron generator, the neutron angular distributions are anisotropic distributions, and they can provide neutrons with an intensity of $ 2.8\times 10^{11}$ n/s (D-D) and $ 1.4\times 10^{13}$ n/s (D-T), respectively, with the deuteron of 450 keV/50 mA.

A compact D–D neutron generator, with a peak neutron yield of D–D reactions up to 2.48 × 108 n/s is being developed at Lanzhou University in China for application in real-time neutron activation analysis. During tests, the problem of back acceleration of secondary electrons liberated from the neutron production target by deuterium ions bombardment was encountered. In this study, an electric field method and a magnetic field method for suppressing secondary electrons are designed and experimentally investigated. The experimental results show that the electric field method is superior to the magnetic field method. Effective suppression of the secondary electrons can be achieved via electrostatic suppression when the bias voltage between the target and the extraction-accelerating electrode is > 204 V. Furthermore, the secondary electron emission coefficient for the mixed deuterium ion (D1+, D2+, and D3+) impacting on molybdenum is estimated. In the deuterium energy range of 80–120 keV, the estimated secondary electron emission coefficients are approximately 5–5.5 for the mixed deuterium ion glancing incidence of 45° and approximately 3.5–3.9 for the mixed deuterium ion normal incidence.

An intense D-T/D-D neutron generator is currently being developed at the Lanzhou University. The Cockcroft–Walton accelerator, as a part of the neutron generator, will be used to accelerate and transport the high-current low-energy beam from the duoplasmatron ion source to the rotating target. The design of a high-current low-energy beam transport (LEBT) line and the dynamics simulations of the mixed beam were carried out using the TRACK code. The results illustrate that the designed beam line facilitates smooth transportation of a deuteron beam of 40 mA, and the number of undesired ions can be reduced effectively using two apertures.

The transport characteristics of a space charge-dominated multi-species deuterium beam consisting of $$ D_{1}^{ + } $$ , $$ D_{2}^{ + } $$ , and $$ D_{3}^{ + } $$ particles in an electrostatic low-energy beam line are studied. First, the envelope equations of the primary $$ D_{1}^{ + } $$ beam are derived considering the space charge effects caused by all particles. Second, the evolution of the envelope of the multi-species deuterium beam is simulated using the PIC code TRACK, with the results showing a significant effect of the unwanted beam on the transport of the primary beam. Finally, different injected beam parameters are used to study beam matching, and a new beam extraction system for the existing duoplasmatron source is designed to obtain the ideal injected beam parameters that allow a $$ D_{1}^{ + } $$ beam of up to 50 mA to pass unobstructed through the electrostatic low-energy beam transport line in the presence of an unwanted ( $$ D_{2}^{ + } $$ , $$ D_{3}^{ + } $$ ) beam of 20 mA; at the same time, distortions of the beam emittance and particle distributions are observed.

The potential-driving model is used to describe the driving potential distribution and to calculate the pre-neutron emission mass distributions for different incident energies in the reaction. The potential-driving model is implemented in Geant4 and used to calculate the fission-fragment yield distributions, kinetic energy distributions, fission neutron spectrum and the total nubar for the reaction. Compared with the built-in G4ParaFissionModel, the calculated results from the potential-driving model are in better agreement with the experimental data and evaluated data. Given the good agreement with the experimental data, the potential-driving model in Geant4 can describe well the neutron-induced fission of actinide nuclei, which is very important for the study of neutron transmutation physics and the design of a transmutation system.

The multi-layer computing model is developed to calculate wide-angle neutron spectra, in the range from 0° to 180° with a 5° step, produced by bombarding a thick beryllium target with deuterons. The double-differential cross-sections (DDCSs) for the 9Be(d, xn) reaction are calculated using the TALYS-1.8 code. They are in agreement with the experimental data, and are much better than the PHITS-JQMD/GEM results at 15° , 30° , 45° and 60° neutron emission angles for deuteron energy of 10.0 MeV. In the TALYS-1.8 code, neutron contributions from direct reactions (break-up, stripping and knock-out reactions) are controlled by adjustable parameters, which describe the basic characteristics of typical direct reactions and control the relative intensity and the position of the ridgy hillock at the tail of DDCSs. It is found that the typical calculated wide-angle neutron spectra for different neutron emission angles and neutron angular distributions agree quite well with the experimental data for 13.5 MeV deuterons. The multi-layer computing model can reproduce the experimental data reasonably well by optimizing the adjustable parameters in the TALYS-1.8 code. Given the good agreement with the experimental data, the multi-layer computing model could provide better predictions of wide-angle neutron energy spectra, neutron angular distributions and neutron yields for the 9Be(d, xn) reaction neutron source.

A fast neutron detector, consisting of a high-density polyethylene sheet, a micro-channel plate, a phosphor screen, a reflection mirror and a CCD camera, is proposed for fast neutron radiography purpose. To optimize the design of the detector, a series of simulations are performed by using Geant4 code. Simulation results indicate that the maximum conversion efficiency of the high-density polyethylene is about 0.38% when its thickness is 2 mm. To ensure the spatial resolution of the detector, the distance between high-density polyethylene and micro-channel plate should be as small as possible. The gap between MCP and PS is selected as 2 mm with a bias voltage of −4 kV to balance the luminescence efficiency and the spatial resolution of the PS. With the optimized structure, the detection efficiency of the detector is calculated to be 0.14% and the spatial resolution is possibly better than 500 μm.

A compact D-D neutron generator was developed at Lanzhou University, China. A duoplasmatron ion source was used to produce a higher-current deuteron beam. The deuteron beam could be accelerated up to 150 keV by a single accelerating gap, and bombarded on a pure molybdenum drive-in target to produce D-D fast neutron. A bias voltage between the target and the extraction-accelerating electrode was produced by a resistance to suppress the secondary electron from the target. The neutron generator has been operated for several hundred hours, and the performances were investigated. The available range of the deuteron beam current was 1.0–4.0 mA. EJ410 scintillator detector system was used to measure the fast neutron yields. D-D neutron yield could reach 2.48×108 n/s under the deuteron beam of 3 mA and 150 keV.

A 400 kV 80 mA Cockcroft-Walton power supply driven by 2.5 kHz frequency, and 12 kW isolation transformer systems are developed for an intense DD/DT neutron generator. The design, construction, and testing of the high voltage (HV) power supply and isolation transformer systems are detailed reported. The structure of step-up transformers can make the potential distribution uniform, and auxiliary coils of the isolation transformers can improve the power transmission efficiency significantly. The testing results show that the HV power supply can reach 400 kV, and the isolation transformer systems can withstand 400 kV voltages and its power transmission efficiency is about 98.1%.

A compact power supply system for a compact neutron generator has been developed. A 4-stage symmetrical Cockcroft-Walton circuit is adopted to produce 250 kV direct current high-voltage. A 2-stage 280 kV isolation transformer system is used to drive the ion source power supply. For a compact structure, safety, and reliability during the operation, the Cockcroft-Walton circuit and the isolation transformer system are enclosed in an epoxy vessel containing the transformer oil whose size is about ∅350 mm × 766 mm. Test results indicate that the maximum output voltage of the power supply is 282 kV, and the stability of the output voltage is better than 0.63% when the high voltage power supply is operated at 250 kV, 6.9 mA with the input voltage varying ±10%.