Neutron Spectrometer Research Articles

Localization of cosmic gamma-ray bursts in interplanetary space with MGNS/BepiColombo and HEND/Mars Odyssey experiments

This paper describes the methods and results for the localization by triangulation of cosmic gamma-ray bursts (GRBs) independently observed by two space experiments: the Mercury Gamma-ray and Neutron Spectrometer (MGNS) and the High Energy Neutron Detector (HEND). MGNS is onboard the MPO/BepiColombo mission and on a stage of cruise to Mercury whereas HEND is onboard Mars Odyssey mission and in orbit around Mars. An analysis is performed of the accuracy of localization of the GRBs jointly observed by the two instruments at interplanetary distances by comparing their light curves. Notable achievements and scientific opportunities are described also in light of the recent inclusion of MGNS within the program of interplanetary network for gamma-ray burst localization (IPN). • A localization procedure by triangulation of cosmic gamma-ray bursts (GRBs) independently observed by two space experiments MGNS and HEND procedure was created. • Describes the methods and results for the localization procedure. • An analysis is performed of the accuracy of localization of the GRBs. A comparison was performed with the localization done by other experiments. • The first results of the MGNS experiment as part of program of interplanetary network (IPN) are described.

A flexible neutron spectrometer concept with a new ultra-high field steady-state vertical-bore magnet.

The proposed facility explores materials under ultra-high magnetic fields. By combining the power of high fields to tune materials and of neutron scattering to probe the resulting changes down to the atomic scale, this facility will enable transformative progress in the study of quantum materials and is named for the "TITAN" subset of Greek gods to reflect this transformation. TITAN will offer DC magnetic fields up to at least 20T. Exploiting the record brightness and bandwidth of the Second Target Station at the Spallation Neutron Source, TITAN will probe atomic-scale responses through high efficiency neutron spectroscopy up to 80meV energy transfer, high resolution diffraction, and small angle neutron scattering. Focusing neutron optics will maximize flux on accurately positioned samples, while radial collimation and optimized shielding and detection strategies will minimize backgrounds.

Performance test of different silicon photomultipliers for the 6LiF:ZnS(Ag) based neutron detectors of CSNS

The China Spallation Neutron Source (CSNS) is a large scientific facility whose main aim is to support multidisciplinary research on material characterization using neutron scattering. Twenty neutron spectrometers will be built as multidisciplinary platforms for scientific research by national institutions, universities, and industry. Scintillator neutron detectors for the spectrometers under construction have recently been developed using silicon photomultipliers (SiPMs) for the readout. This paper studies the characteristics of three candidate SiPMs, including the breakdown voltage, gain, temperature coefficient, dark count rate, and radiation tolerance. Two measurement platforms were built to evaluate each SiPM. We summarize the results from our analysis of laboratory tests and beam test data to characterize the performance of the SiPMs. The MicroFJ-30035-TSV SiPM manufactured by the SensL Corporation is chosen as the best SiPM for the scintillator detectors at CSNS.

Моделирование и оптимизация состава детекторов в многодетекторном нейтронном спектрометре реального времени

The article continues the series of articles devoted to the problem of creating a real-time multi-detector neutron spectrometer. It considers the problem of choosing the optimal combination of detectors§measuring channels, which ensures the minimization of errors in the reconstruction of the spectral components of the measured flow with a minimum number of detectors used. To solve it, a simulation system for such a spectrometer with various combinations of measurement channels used was developed, with an estimate of the errors in reconstructing the spectral components of an extensive sample of neutron fluxes with a variety of energy spectrum shapes.

Исследование и подавление чувствительности нейтронных сцинтилляционных детекторов к гамма-излучению

The article continues the consideration of the main problems arising in the development of a real-time multi-detector neutron spectrometer. In previous articles [1,2], possible ways of forming the spectral characteristics of polystyrene scintillation neutron detectors and the results of their calculation using the GEANT-4 modeling software library [1] and restoring the absolute values of the spectral components of the measured neutron flux from their normalized values determined with using a pretrained neural network based on the responses of detectors used in the spectrometer with different spectral characteristics [2]. This article presents the results of studying the processes of scintillation initiation in organic scintillators under the influence of neutron and gamma radiation and considers possible methods for suppressing the sensitivity of a multi-detector neutron spectrometer to accompanying gamma radiation.

A high-resolution neutron spectroscopic camera for the SPARC tokamak based on the Jet European Torus deuterium-tritium experience.

Dedicated nuclear diagnostics have been designed, developed, and built within EUROFUSION enhancement programs in the last ten years for installation at the Joint European Torus and capable of operation in high power Deuterium-Tritium (DT) plasmas. The recent DT Experiment campaign, called DTE2, has been successfully carried out in the second half of 2021 and provides a unique opportunity to evaluate the performance of the new nuclear diagnostics and for an understanding of their behavior in the record high 14MeV neutron yields (up to 4.7 × 1018 n/s) and total number of neutrons (up to 2 × 1019n) achieved on a tokamak. In this work, we will focus on the 14MeV high resolution neutron spectrometers based on artificial diamonds which, for the first time, have extensively been used to measure 14MeV DT neutron spectra with unprecedented energy resolution (Full Width at Half Maximum of ≈1% at 14 MeV). The work will describe their long-term stability and operation over the DTE2 campaign as well as their performance as neutron spectrometers in terms of achieved energy resolution and high rate capability. This important experience will be used to outline the concept of a spectroscopic neutron camera for the SPARC tokamak. The proposed neutron camera will be the first one to feature the dual capability to measure (i) the 2.5 and 14MeV neutron emissivity profile via the conventional neutron detectors based on liquid or plastics scintillators and (ii) the 14MeV neutron spectral emission via the use of high-resolution diamond-based spectrometers. The new opportunities opened by the spectroscopic neutron camera to measure plasma parameters will be discussed.

Neutron emission spectrometer to measure ion temperature on the Fusion Demonstration Plant.

General Fusion is building the Fusion Demonstration Plant to demonstrate a magnetized target fusion scheme in which a deuterium plasma is heated from 200eV to 10keV by piston-driven compression of a liquid-lithium liner. The multilayer coaxial time-of-flight neutron emission spectrometer is designed to measure the ion temperature near peak compression at which time the neutron yield will approach 1018 neutrons/s. The neutron energy distribution is expected to be Gaussian since the machine uses no neutral beam or radio-frequency heating. In this case, analysis shows that as few as 500 coincidence events should be sufficient to accurately measure the ion temperature. This enables a fast time resolution of 10 µs, which is required to track the rapid change in temperature approaching peak compression. We overcome the challenges of neutron pile-up and event ambiguity with a compact design having two layers of segmented scintillators. The error in the ion temperature measurement is computed as a function of the neutron spectrometer's geometric parameters and used to optimize the design for the case of reaching 10keV at peak compression.

P-82 - Designing and validating the nested neutron spectrometer using for accelerator-based neutron source: Monte Carlo code and artificial intelligence algorithm

P-82 - Designing and validating the nested neutron spectrometer using for accelerator-based neutron source: Monte Carlo code and artificial intelligence algorithm

A novel experimental approach to characterize neutron fields at high- and low-energy particle accelerators

The characterization of particle accelerator induced neutron fields is challenging but fundamental for research and industrial activities, including radiation protection, neutron metrology, developments of neutron detectors for nuclear and high-energy physics, decommissioning of nuclear facilities, and studies of neutron damage on materials and electronic components. This work reports on the study of a novel approach to the experimental characterization of neutron spectra at two complex accelerator environments, namely the CERF, a high-energy mixed reference field at CERN in Geneva, and the Bern medical cyclotron laboratory, a facility used for multi-disciplinary research activities, and for commercial radioisotope production for nuclear medicine. Measurements were performed through an innovative active neutron spectrometer called DIAMON, a device developed to provide in real time neutron energy spectra without the need of guess distributions. The intercomparison of DIAMON measurements with reference data, Monte Carlo simulations, and with the well-established neutron monitor Berthold LB 6411, has been found to be highly satisfactory in all conditions. It was demonstrated that DIAMON is an almost unique device able to characterize neutron fields induced by hadrons at 120 GeV/c as well as by protons at 18 MeV colliding with different materials. The accurate measurement of neutron spectra at medical cyclotrons during routine radionuclide production for nuclear medicine applications is of paramount importance for the facility decommissioning. The findings of this work are the basis for establishing a methodology for producing controlled proton-induced neutron beams with medical cyclotrons.

Fuel ion ratio determination using the 14 MeV Tandem neutron spectrometer for JET DTE1 campaign discharges

This paper investigates the determination of the fuel ion ratio nT/ntot in fusion experiments using two different approaches. The methods are applied to plasma discharges from the deuterium–tritium campaign at the Joint European Torus (JET) in 1997. Multiple discharges have been analysed using data acquired with the Tandem (KM2) neutron spectrometer, using a new neutron spectrometer response function and improved line-of-sight information.The two different approaches were generally similar with the exception of the beam slowing down modelling, handled by two different particle transport codes, namely, TRANSP and PENCIL.The results show that nT/ntot can be determined using Tandem neutron spectrometer data; nT/ntot using both of the approaches are consistent and within the uncertainty for a range of studied discharges.The obtained results support previous studies on nT/ntot determination using neutron spectroscopy. In addition, we have shown that PENCIL can be used instead of TRANSP for a range of discharges which could simplify and speed up the estimation of nT/ntot. The possible limitations of the approach using PENCIL could be investigated using different neutron spectrometer data from the 2021 JET deuterium–tritium campaign.A similar spectrometer like Tandem is planned to be operational at ITER and the results of this paper form the first experimental verification of the capability for nT/ntot measurements with such spectrometers. Further research on this could lead to better understanding of these instruments and their limitations before the start of experiments at ITER.

Miniature semiconductor neutron spectrometer HardPix for surface mapping of lunar water

A current renaissance of lunar exploration enables to search for lunar water deposits directly on the surface of the Moon with robotic rovers. We present a novel miniature semiconductor neutron spectrometer capable of mapping the water deposits using non-invasive detection of neutrons created underground by cosmic rays and thermalized by hydrogen. This prospecting package consists of a radiation detector to monitor the cosmic rays background, a thermal/epithermal neutron detector to measure flux of neutrons moderated by water, and a gamma spectrometer suitable for monitoring local changes of major elemental components of the lunar regolith. Using miniature semiconductor detectors allows to deploy them even on small commercial rovers where resources are extremely limited. The prospecting package is being developed for ispace lunar rover and studied for ESA EL3 rover. It is based on Timepix pixel sensors, with space heritage onboard NASA, ESA and JAXA vessels.

Neutron spectrum unfolding of the magnetic proton recoil spectrometer using the GRAVEL and MLEM algorithms

The magnetic proton recoil (MPR) spectrometer is a high-resolution neutron spectrometer, which provides critical information about the deuterium–tritium (DT) fusion yield, collective fuel velocity, and ion temperature. For precise measurements, the MPR spectrometer operates in a high-resolution mode; however, its detection efficiency is low. The trade-off between energy resolution and detection efficiency limits its widespread applications. Herein, we apply the spectrum unfolding technique to obtain a precise energy spectrum using the MPR spectrometer in a low-resolution mode and to achieve high detection efficiency. Numerical experiments and Geant4 simulations are conducted to compare the GRAVEL and the maximum likelihood expectation maximization (MLEM) algorithms in different cases. A new stopping criterion for iterations is adopted and works well. The source focuses on the primary DT neutrons with single Gaussian, asymmetric, and dual Gaussian distributions. All the cases demonstrate an accurate and stable unfolded energy spectrum, revealing the potential of the MPR spectrometer in a wide range of applications.

Experimental characterisation of diamond-based neutron spectrometer

The results of testing and characterisation of the neutron spectrometer based on a diamond detector are presented. It is shown that spectrometer calibration with monoenergetic electrons and alpha-particles leads to different results. The energy resolution of the spectrometer is estimated based on the experiments with alpha-particles and with DT-neutrons from NG-150M neutron generator. It has been shown experimentally that for neutrons with an energy of 14 MeV the energy resolution of a diamond-based spectrometer is 0.6%.

On the spectral resolution of the broad-band indirect-geometry time-of-flight neutron spectrometer TOSCA

We present a detailed description of the spectral resolution of the TOSCA spectrometer at the ISIS Neutron and Muon Source. We compare an analytical model of the resolution, a numerical model based on ray-tracing simulations and experimental data derived from measurements of the 2,5-diiodothiophene standard. The analytical description is derived by error propagation on the energy transfer equation and accurately accounts for the dimensions of each of the component of the instrument and their neutron scattering or absorption depth-profiles. We obtain excellent agreement between the analytical and numerical descriptions for the ideal time-focusing geometry of TOSCA and also between the simulations of a more realistic model of the instrument and the experimental data. This study provides several insights into the critical contributions to the instrument performance that are directly useful for the proposed upgrade of TOSCA, but also relevant for other broad-band crystal-analyser spectrometers.

Формирование и расчет спектральных характеристик сцинтилляционных нейтронных детекторов

The concept of creating a real-time multi-detector neutron spectrometer is briefly outlined. It is shown that the main problem of its implementation is the lack of neutron detectors with diverse and precisely known spectral characteristics in the neutron energy range from 0.001 eV to 20 MeV. It is proposed to use scintillation polystyrene neutron detectors for these purposes, and four methods for forming various spectral characteristics of such detectors are described. A method for calculating spectral characteristics using a microscopic approach is substantiated. The results of calculating the spectral characteristics of such detectors using all four proposed methods for their formation are presented.

A fully-automated, liquid-moderated neutron spectrometer system

A novel, water-based, neutron spectroscopy system has been designed, simulated, and tested at the National Research Council of Canada. The active part of the detection system is a small proportional counter sensitive to thermal neutrons. The proportional counter is suspended along the symmetry axis of a large, rectangular water bath, and can be positioned remotely anywhere along this axis down to the bottom face. Measured count rates as a function of depth of the counter for both an americium–beryllium and a californium-252 neutron source demonstrate the ability of the system to discriminate between sources with different energy spectra. An MCNP6 simulation of an AmBe source agrees with the data within uncertainties at the 2%-level and is used to construct the response functions of the spectrometer system. Unfolded energy spectra are determined using an analysis of the singular value decomposition of the response matrix. Finally, a Monte Carlo study of the system indicates an ability to measure the fluence rate of the radionuclide sources.

The CLYC-7 scintillator as a fast neutron spectrometer: Pulse-shape discrimination for different neutron-induced reaction channels

The CLYC-7 scintillators (Cs2LiYCl6) are being studied for their capability to detect and discriminate both γ-ray radiation and neutrons in a wide energy range. Different Pulse-Shape Analysis (PSA) techniques were developed to perform this distinction, with excellent results. An intrinsic problem resides in the neutron detection mechanism, which occurs mainly via two nuclear reactions on the chlorine nucleus: 35Cl(n,p)35S and 35Cl(n,α)32P. In the latter, the neutron energy reconstruction turns out to be more difficult, due to the large variety of excited states (and therefore reaction Q values) of 32P. A particular PSA algorithm was investigated to perform this α background rejection, with interesting results in different energy ranges.

High-yield magnetic recoil neutron spectrometer on the National Ignition Facility for operation up to 60 MJ.

Recent progress at the National Ignition Facility (NIF), with neutron yields of order 1 × 1017, places new constraints on diagnostics used to characterize implosion performance. The Magnetic Recoil neutron Spectrometer (MRS), which is routinely used to measure yield, ion temperature (Tion), and down-scatter ratio (dsr), has been adapted to allow measurements of dsr up to 5 × 1017, and yield and Tion up to 2 × 1018 in the near term with new data processing techniques and conversion foil solutions. This paper presents a solution for extending MRS operation up to a yield of 2 × 1019 (60 MJ) by moving the spectrometer outside of the NIF shield wall. This will not only enhance the upper yield limit by 10× but also improve signal-to-background by 5×.

Development of novel crystal scintillators for lunar surface science

The development of novel crystal scintillators for a lunar landed mission near future is reported. On that mission, we aim to assess the radiation dose, biological effect, water, and other resources on the lunar surface. To accomplish this, a Lunar Vehicle Radiation Dosimeter (LVRAD) made up of several radiation detectors has been proposed. New scintillation crystals are being developed for neutron and gamma measurements. Stilbene and undoped LaCl3 crystal were selected for fast neutron/gamma spectrometers. The mutual combination of organic and inorganic detectors benefits from direct fast neutron detection via 35Cl(n, p)35S reaction as well as the good gamma resolution of LaCl3 and the high detection efficiency of stilbene. LaCl3 crystals with the diameter of 38.1 mm were grown by a homemade modified Bridgman furnace. For epithermal neutron spectrometer, 6LiI:Ag crystal was selected due to its pulse shape discrimination capability and highest detection efficiency in terms of size for both thermal and epithermal neutron among scintillation materials. Enrich 6LiI was purified using the zone-refining technique. The crystal was then grown by the same Bridgman furnace.

A TOF spectrometer for neutron spectral measurements in a wide energy range base on a fast ionization chamber containing 6Li-235U

ABSTRACT To measure the neutron spectra in a wide energy range at the China Spallation Neutron Source (CSNS), a time of flight (TOF) neutron spectrometer based on a fast ionization chamber (FIC) containing 6Li and 235U has been developed. Verification experiments have been performed at the BL09 test beam line at the CSNS, which demonstrated that the measured neutron spectra, analyzed with a spectrum-splicing technique, ranging from sub-meV to 10 keV with a limited flight path. Comparisons demonstrated that the integral thermal neutron fluence obtained by the TOF spectrometer and the cadmium difference activation measurements used were in good agreement. Moreover, the measured neutron spectra agreed well with the Monte Carlo simulations. This shows that the developed equipment and the measurement methods are reliable.