Intense Neutron Source Research Articles

A pulse current generator for dense plasma focus

A pulse current generator applied in a type of high-yield intense pulsed neutron source, the Dense Plasma Focus (DPF), is designed and developed in this paper. There are three key components in this generator. Each group of capacitors and switches is integrative to meet the DPF's requirements of low circuit inductance. A coaxial multi-channel switch is developed to solve the problems of the switch inductance, the jitter and the electrode erosion. A kind of sectorial plate transmission line is adopted to transfer the high pulse current from the capacitors to the DPF. The following technical parameters of the generator were achieved on dummy load: output current amplitude of ∼560 kA when primary capacitors are charged with 22 kV.

Boron neutron capture therapy in clinical application:Progress and prospect

<p indent="0mm">Boron neutron capture therapy (BNCT) is an emerging radiotherapeutic modality aimed at selectively concentrating boron compounds in tumor cells and then subjecting the tumor cells to neutron beam radiation. Treatment with BNCT is based on the nuclear capture and fission reactions that occur when nonradioactive boron-10 (¹⁰B) is irradiated with neutrons to yield an alpha particle (helium, ⁴He) and a recoiling lithium-7 (⁷Li) nuclei. The ⁴He particle has a range of <sc>9 μm</sc> and the ⁷Li particle <sc>5 μm</sc> in tissue. In theory, the short range of this reaction limits the damage to malignant cells while sparing adjacent normal cells. The development of BNCT is still constrained by the progress in developing boron delivery agents with a high tumor uptake, low normal tissue uptake, and optimizing the dosing paradigms and quantitative estimation of the ¹⁰B concentrations. It is widely recognized that the second generation boron-containing agents, sodium borocaptate (BSH) and boronophenylalanine (BPA), are less than ideal. New and more effective boron-containing agents are urgently required for clinical use to deliver the requisite amounts of boron to tumor cells. The delivery of boron-containing agent can also be optimized to improve cancer cell uptake and subcellular distribution. Additionally, it is crucial to design high intensity neutron sources and establish hospital-based BNCT. Compared with nuclear reactors, accelerator-based neutron sources are more realistic to be applied in clinical practice. In future, the critical issues regarding novel boron-containing agents, the appropriate delivery strategies, and neutron sources of BNCT for clinical use must be addressed. Two clinical trials with newly diagnosed glioblastoma have been reported, BNCT alone after surgery provided a mean survival time of 17.7 and <sc>19.5 months</sc> respectively. The survival outcomes were good as compared to the current standard of care which is post-operation fractionated radiotherapy with concomitant and adjuvant TMZ. Several clinical studies of BNCT in the treatment of recurrent head and neck cancer have been reported, with high response rate and acceptable toxicity. To date, BNCT has been clinically evaluated as an alternative to conventional radiotherapy for the treatment of several tumor types, including newly diagnosed glioblastoma, recurrent glioma, recurrent head and neck tumors, meningioma, malignant melanoma, and liver metastasis. Recently, accelerator-based neutron source has been used in clinical trials for recurrent malignant gliomas and head &amp; neck cancers. Although initial results with BNCT are promising, high-quality prospective clinical trials are still lacking. Well-designed phase II/III clinical research is necessary to define the efficacy and safety of BNCT in various tumor types. Meanwhile, studies comparing the outcomes of BNCT with other standards of care are needed for the further development of BNCT. Based on the previous studies, the BNCT clinical trials in glioblastoma can be initiated with newly diagnosed glioblastoma patients. For other tumor types, late-stage patients with recurrent or metastatic disease after the first-line treatment might be recruited. Last but not the least, in the era of comprehensive treatment for malignant tumor, it is necessary to explore the combined treatment mode of BNCT. For the future research, BNCT may be coupled with a variety of anti-tumor modalities, including traditional photon radiotherapy, immunotherapy, targeted therapy and chemotherapy. It is also possible to explore a variety of drug delivery methods to improve the uptake of boron-containing agents by tumor sites. Multidisciplinary model is needed to jointly promote BNCT to become a routine clinical treatment modality.

Power control of CiADS core with the intensity of the proton beam

This paper reports the control method for the core power of the China initiative Accelerator Driven System (CiADS) facility. In the CiADS facility, an intense external neutron source provided by a proton accelerator coupled to a spallation target is used to drive a sub-critical reactor. Without any control rod inside the sub-critical reactor, the core power is controlled by adjusting the proton beam intensity. In order to continuously change the beam intensity, an adjustable aperture is considered to be used at the Low Energy Beam Transport (LEBT) line of the accelerator. The aperture size is adjusted based on the Proportional Integral Derivative (PID) controllers, by comparing either the setting beam intensity or the setting core power with the measured value. To evaluate the proposed control method, a CiADS core model is built based on the point reactor kinetics model with six delayed neutron groups. The simulations based on the CiADS core model have indicated that the core power can be controlled stably by adjusting the aperture size. The response time in the adjustment of the core power depends mainly on the adjustment time of the beam intensity.

A prototype compact accelerator-based neutron source (CANS) for Canada

Canada’s access to neutron beams for neutron scattering was significantly curtailed in 2018 with the closure of the National Research Universal (NRU) reactor in Chalk River, Ontario, Canada. New sources are needed for the long-term; otherwise, access will only become harder as the global supply shrinks. Compact Accelerator-based Neutron Sources (CANS) offer the possibility of an intense source of neutrons with a capital cost significantly lower than spallation sources. In this paper, we propose a CANS for Canada. The proposal is staged with the first stage offering a medium neutron flux, linear accelerator-based approach for neutron scattering that is also coupled with a boron neutron capture therapy (BNCT) station and a positron emission tomography (PET) isotope production station. The first stage will serve as a prototype for a second stage: a higher brightness, higher cost facility that could be viewed as a national centre for neutron applications.

Clustering of Diamond Nanoparticles, Fluorination and Efficiency of Slow Neutron Reflectors.

Neutrons can be an instrument or an object in many fields of research. Major efforts all over the world are devoted to improving the intensity of neutron sources and the efficiency of neutron delivery for experimental installations. In this context, neutron reflectors play a key role because they allow significant improvement of both economy and efficiency. For slow neutrons, Detonation NanoDiamond (DND) powders provide exceptionally good reflecting performance due to the combination of enhanced coherent scattering and low neutron absorption. The enhancement is at maximum when the nanoparticle diameter is close to the neutron wavelength. Therefore, the mean nanoparticle diameter and the diameter distribution are important. In addition, DNDs show clustering, which increases their effective diameters. Here, we report on how breaking agglomerates affects clustering of DNDs and the overall reflector performance. We characterize DNDs using small-angle neutron scattering, X-ray diffraction, scanning and transmission electron microscopy, neutron activation analysis, dynamical light scattering, infra-red light spectroscopy, and others. Based on the results of these tests, we discuss the calculated size distribution of DNDs, the absolute cross-section of neutron scattering, the neutron albedo, and the neutron intensity gain for neutron traps with DND walls.

Soft Matter Sample Environments for Time-Resolved Small Angle Neutron Scattering Experiments: A Review

With the promise of new, more powerful neutron sources in the future, the possibilities for time-resolved neutron scattering experiments will improve and are bound to gain in interest. While there is already a large body of work on the accurate control of temperature, pressure, and magnetic fields for static experiments, this field is less well developed for time-resolved experiments on soft condensed matter and biomaterials. We present here an overview of different sample environments and technique combinations that have been developed so far and which might inspire further developments so that one can take full advantage of both the existing facilities as well as the possibilities that future high intensity neutron sources will offer.

Strategical Approach for the Neutronics in the European Fusion Programme

One of the main aims of the European fusion programme is the design of a DEMOnstration fusion power plant (DEMO). The related work is conducted by the EUROfusion consortium and includes a strong supporting research and development programme. Support is also provided to the design of the high intense neutron source IFMIF-DONES (International Fusion Material Irradiation Facility-DEMO Oriented NEutron Source) to be built for the qualification of materials considered for DEMO. Neutronics plays a fundamental role for the design, operation, and safety of these facilities including the evaluation and verification of their nuclear performance. The lessons learned during the ITER design and construction phase point to the need to strengthen nuclear design integration already in the early DEMO design phase and establish an improved nuclear safety culture. This requires a coordinated approach for the neutronics that relies upon the availability of suitable computational procedures, tools, and data, qualified and validated for specific design- and safety-related applications. Accordingly, the approach builds on the development of advanced computation tools and the provision of high-quality nuclear data supported by integral experiments for their validation. Furthermore, configuration and requirement management principles ensure the alignment with the global nuclear design integration. This translates into appropriately chosen design margins and acceptance criteria, along with the specification of the nuclear analyses to be conducted in the various design phases. This paper presents the outlined approach as implemented in the EUROfusion Power Plant Physics and Technology (PPPT) programme and provides a strategical outlook of planned activities. This includes development works on advanced simulation tools with their application in various nuclear design- and safety-related analyses. The efforts to improve the nuclear database, in particular, with regard to radiation damage and activation cross-section data relevant to DEMO and DONES, are highlighted. Furthermore, the methodological approach applied to PPPT nuclear analyses including design, shielding, activation, and radiation dose calculations is discussed on the basis of specific examples.

Neutronics study of a subcritical system driven by external neutron source for 99Mo production

A subcritical system with the Low Enriched Uranium (LEU) solution was proposed to produce 99Mo, which is driven by an external D–T neutron source. The neutronics model of the subcritical system is approximately a concentric cylindrical structure with the maximum radius and height of the system as limited to 100 cm and 150 cm, respectively. The materials and dimensions of the zones were designed based on neutronics analysis including the sub-critical multiplication factor ks and distribution of neutron flux to achieve high production of 99Mo, as well as to keep the system in a safe and deep sub-critical state (i.e. 0.90<ks<0.95). With intensity of neutron source as 5 × 1013 n/s, the yield of 99Mo in the system can reach to 167 Ci/day, which could be used for around ten thousand nuclear medical procedures.

EXPERIMENTAL STUDY ON NEUTRON CORRELATION ANALYSIS FOR A SUBCRITICAL SYSTEM DRIVEN BY A PULSED SPALLATION NEUTRON SOURCE IN KUCA

The Feynman-α and the Rossi-α methods have been frequently employed to determine the subcriticality of subcritical reactor systems driven by Poisson source such as Am-Be neutron source. In actual accelerator-driven systems (ADS), a spallation device will be applied as an intense neutron source. This device will be probably operated in a pulse mode and it is impossible to apply a conventional analysis method to determine the subcriticality in any ADS. In previous theoretical studies, some advanced formulae of neutron correlation analysis for spallation neutron source have been presented. However, the experimental study has been hardly reported to date. The major objectives of this study are to examine experimentally an applicability of these complicated formulae to a subcritical reactor system driven by an actual pulsed spallation neutron source and to determine the prompt-neutron decay constant α of the system. To achieve these goals, we constructed an ADS core at the Kyoto University Critical Assembly (KUCA). The core was composed of highly-enriched uranium fuel assemblies surrounded by many polyethylene reflector assemblies. We carried out a series of the Feynman-α and the Rossi-α analyses for the system driven by pulsed spallation source. As a result, the prompt-neutron decay constants were experimentally obtained by using a fitting formula. The prompt-neutron decay constants determined by Feynman-α and Rossi-α analyses agrees with each other within a statistical error range of least-squares fitting.

A non-intercepting monitoring method for beam position on the target in an accelerator driven system

In an accelerator driven sub-critical system (ADS), an intense external neutron source provided by an accelerator coupled to a target is used to drive a sub-critical reactor. To ensure the stable operation of the reactor, it is of crucial importance to locate the beam spot on the target during the operation. In this paper, we have proposed a method for beam position measurement on the target’s beam entrance window. The proposed method is to measure the neutron flux outside the spallation target in the four directions of the east, south, west, and north. Since the neutron flux decreases with the distance between the detector and the beam center, the position of the beam center on the target’s entrance window can be extracted from the measured four neutron fluxes. The simulations based on FLUKA and OpenMC codes have indicated that the x and y positions of the beam center can be extracted from the measured four neutron fluxes. Since the four neutron detectors are fixed inside the reactor core, this method allows for continuous measurement of the beam position.

Tuning Neutron Resonance Spin-Echo Spectrometers with Pulsed Beams

The neutron spin-echo spectroscopy technique involving pulsed beams can be used to effectively access a wide range of space-time correlations of condensed matter. In this study, the features of this technique, in particular, the modulation of the intensity with zero effort (MIEZE) by using pulsed beams, which is based on the quantum-state manipulation of the neutron spin and energy, are comprehensively examined. A formulation of the MIEZE combined with the time of flight method (TOF MIEZE) is established by considering the characteristics of the pulsed neutron beams. Moreover, a parameter, namely, the detuning parameter, is introduced as a measure of the magnitude of detuning from the optimized instrumental state, known as the spin-echo condition. The phase and frequency shifts of the neutron intensity signals resulting from the TOF MIEZE under various configurations are investigated systematically. It is found that the detuning parameter equals the derivative of phase with respect to the TOF, whose zero-point corresponds to the spin-echo condition. The theoretical predictions on phase and frequency shifts by the established formulation are well validated by the experiments using an intense pulsed neutron source. The detuning parameter helps clarify the principle of the TOF MIEZE technique and can provide practical guidance regarding the implementation and optimization of spectrometers.

LUE-200 Accelerator—A Photo-neutron Generator For The Pulsed Neutron Source “IREN”

This article reports about the construction and status of the accelerator facility at the Laboratory of Neutron Physics (FLNP) in the Joint Institute for Nuclear Research (JINR, Dubna), the driver of an intense pulsed resonance neutron source. The general scheme of the electron linear accelerator and features of its basic systems are presented. LUE-200 consists of two accelerating sections on a traveling wave with an operating frequency of 2856 MHz with RF power compression systems of the SLED type. The pulse current of the beam at the output of the accelerator reaches 2 A with a pulse duration of 80–100 ns. At the average energy of beam particles from 60–65 MeV and a cycle repetition rate of 50 Hz, the average beam power reaches ≈ 600 W. The integral neutron flux from the non-multiplying target reaches ∼ 1012 s−1.

Metrological characterization of intense ([formula omitted], n) neutron sources by coupling of non-destructive measurements

Metrological non-destructive characterization of intense (α, n) neutron sources (emission rate between 107 and 3×108 s−1 into 4π sr solid angle) is a challenge for nuclear applications. In this article, we will present the design, development and in situ validation of two measurement cells especially dedicated to this characterization. The main goal consists in determining the absolute neutron emission rate of this type of neutron sources with relative uncertainties less than 5% (k=1). Another purpose is related to the qualitative and quantitative analysis of fission products present in irradiated neutron sources. Because of experimental constraints, acquisitions were carried out underwater which required a full remote control of the measurement cells. Neutron emission rate is assessed using three different non-destructive techniques: (i) global neutron counting, (ii) neutron activation using gold dosimeters and (iii) gamma-ray spectrometry. We will successively present the design step and associated constraints, main characteristics of measurement cells and associated laboratory characterization as well as experimental results obtained during the final in situ measurement campaign. The latter shows an excellent agreement regarding the neutron emission rate values provided by the three different non-destructive techniques and a relative combined standard uncertainty less than 5% (k=1) for the investigated neutron sources.

Frequency domain Monte Carlo simulations of void velocity measurements in an actual experimental setup using a neutron noise technique

ABSTRACT Monte Carlo simulations of the void velocity measurement in a light-water moderated critical assembly CROCUS are performed using a continuous energy Monte Carlo code that has a special function to conduct frequency domain calculations using complex-valued weights of neutron noise. In the measurements that are simulated in this paper, two vertically aligned fission chambers detected the neutron noise caused by the upward moving void in a rectangular channel. The neutron noise transport calculations in the frequency domain are performed for the measurement simulations. Using the cross power spectral density between two chambers, the void velocities are calculated at frequencies from 0.1 to 12 Hz. The void velocity is overestimated at lower frequencies, and accurately predicted at higher frequencies. This frequency dependence is explained using a simple model that takes neutron noise spatial attenuation and source intensity distribution into consideration.

Achieving reliable UDP transmission at 10 Gb/s using BSD socket for data acquisition systems

User Datagram Protocol (UDP) is a commonly used protocol for data transmission in small embedded systems. UDP as such is unreliable and packet losses can occur. The achievable data rates can suffer if optimal packet sizes are not used. The alternative, Transmission Control Protocol (TCP) guarantees the ordered delivery of data and automatically adjusts transmission to match the capability of the transmission link. Nevertheless UDP is often favored over TCP due to its simplicity, small memory and instruction footprints. Both UDP and TCP are implemented in all larger operating systems and commercial embedded frameworks. In addition UDP also supported on a variety of small hardware platforms such as Digital Signal Processors (DSP) Field Programmable Gate Arrays (FPGA). This is not so common for TCP. This paper describes how high speed UDP based data transmission with very low packet error ratios was achieved. The near-reliable communications link is used in a data acquisition (DAQ) system for the next generation of extremely intense neutron source, European Spallation Source. This paper presents measurements of UDP performance and reliability as achieved by employing several optimizations. The measurements were performed on Xeon E5 based CentOS (Linux) servers. The measured data rates are very close to the 10 Gb/s line rate, and zero packet loss was achieved. The performance was obtained utilizing a single processor core as transmitter and a single core as receiver. The results show that support for transmitting large data packets is a key parameter for good performance. Optimizations for throughput are: MTU, packet sizes, tuning Linux kernel parameters, thread affinity, core locality and efficient timers.

Beam dynamics design and error study of BISOL deuteron driver linac

The high intensity deuteron linac, one of the drivers of BISOL, aims to accelerate a continuous wave (cw) deuteron beam up to 40 MeV with a beam current of 20 mA, which can also be operated independently as the Multi-Aimed Intense Neutron Source (MAINS). As the high beam power and beam current, high reliability and strict beam loss are demand for the deuteron driver linac. The beam dynamics design of the driver linac, including the radio frequency quadrupole (RFQ), medium energy beam transport line (MEBT) and superconducting rf (SRF) linac, has been designed and optimized to meet the required requirements. In order to prevent halo formation and achieve strict beam losses, beam halo matching is implemented in our design. The simulation results predict a transmission efficiency of above 99% and the beam power losses meet requirements of less than l W/m in the SRF linac. Detailed error studies are performed to evaluate the sensitivity of the bean dynamics design at last. The general design considerations and the overall beam dynamics of the driver linac are presented in this paper.

High-precision and wide-range real-time neutron flux monitor system through multipoint linear calibration

The neutron flux monitor (NFM) system is an important diagnostic subsystem introduced by large nuclear fusion devices such as international thermonuclear experimental reactor (ITER), Japan torus-60, tokamak fusion test reactor, and HL-2A. Neutron fluxes can provide real-time parameters for nuclear fusion, including neutron source intensity and fusion power. Corresponding to different nuclear reaction periods, neutron fluxes span over seven decades, thereby requiring electronic devices to operate in counting and Campbelling modes simultaneously. Therefore, it is crucial to design a real-time NFM system to encompass such a wide dynamic range. In this study, a high-precision NFM system with a wide measurement range of neutron flux is implemented using real-time multipoint linear calibration. It can automatically switch between counting and Campbelling modes with variations in the neutron flux. We established a testing platform to verify the feasibility of the NFM system, which can output the simulated neutron signal using an arbitrary waveform generator. Meanwhile, the accurate calibration interval of the Campbelling mode is defined well. Based on the above-mentioned design, the system satisfies the requirements, offering a dynamic range of 108 cps, temporal resolution of 1 ms, and maximal relative error of 4% measured at the signal-to-noise ratio of 15.8 dB. Additionally, the NFM system is verified in a field experiment involving HL-2A, and the measured neutron flux is consistent with the results.

Development of a Technique for the Express Assessment of Temperature Fields on the Outlet Window Membrane of the LUE-200 Accelerator

A technique has been developed for express estimation of temperature fields using a graded curve, which can be used to justify the reliability and safety of operation of the outlet window membrane of the LUE‑200 accelerator—a driver of a pulsed Intense Resonance Neutron source (IREN). For this purpose, a multivariate numerical simulation was carried out using the developed computational models of the transportation channel and the outlet window membrane.

Preliminary design of the RF driven positive deuterium ion source at HUST

Huazhong University of Science and Technology (HUST) plans to develop a radio frequency (RF) ion source experimental setup for a high intensity neutron source which is at the conceptual design stage. The positive deuterium ion beam with the current of ∼14.5 A, the energy of 20 keV and the pulse length of ∼2 s is required. This paper introduces the RF driven deuterium ion source, and focuses on the design of the extraction systems. A triode extraction system is optimized to deliver the beam well inside the required divergence by means of ion beam optics simulation. Finite element calculations have been carried out to analyze the temperature and deformation of the electrode under heat power loads.

Verification of accuracy of contact-probe distance meter for lithium target of fusion neutron source

Abstract An accelerator based intense neutron sources such as the IFMIF, A-FNS and DONES produce neutron flux by a stripping reaction between lithium (Li) and deuteron for testing various materials for fusion reactor. In these fusion neutron sources, a liquid Li free-surface jet is applied as the liquid Li target. For the development of the Li target system, the variation in the thickness of the Li jet was measured using the Li loop of Osaka University. At the Osaka Univ., a lot of knowledge about the surface fluctuation of the Li jet had been obtained by using the electro-contact type distance meter (referred to as the probe apparatus herein). Besides, for the stable and safety operation of the facility, the probe apparatus is planned to be used as a safety interlock system for beam irradiation in actual intense neutron source because of its simple structure. Therefore, it is desirable to verify its accuracy. Especially, it is expected that false detection and undetected waves, which is particular to the contact-type apparatus, could cause errors. Then in this study, the measurement using non-contact type distance meter using optical comb (referred to as the laser probe herein) was conducted, and then the error of the results of the probe apparatus is evaluated by comparing results.