| 1. |
- Carlson, A. D., et al.
(författare)
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A new evaluation of the neutron data standards
- 2017
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Ingår i: ND 2016. - : EDP Sciences. - 9782759890200
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Konferensbidrag (refereegranskat)abstract
- Evaluations are being done for the H(n,n), 6Li(n,t), 10B(n,αγ), 10B(n,α), C(n,n), Au(n,γ), 235U(n,f) and 238U(n,f) standard cross sections. Evaluations are also being done for data that are not traditional standards including: the Au(n,γ) cross section at energies below where it is considered a standard; reference cross sections for prompt gamma-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the 235U thermal neutron fission spectrum and the 252Cf spontaneous fission neutron spectrum and the thermal constants.
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| 2. |
- Carlson, A. D., et al.
(författare)
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Evaluation of the Neutron Data Standards
- 2018
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Ingår i: Nuclear Data Sheets. - : Elsevier BV. - 0090-3752 .- 1095-9904. ; 148, s. 143-188
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Tidskriftsartikel (refereegranskat)abstract
- With the need for improving existing nuclear data evaluations, (e.g., ENDF/B-VIII.0 and JEFF-3.3 releases) the first step was to evaluate the standards for use in such a library. This new standards evaluation made use of improved experimental data and some developments in the methodology of analysis and evaluation. In addition to the work on the traditional standards, this work produced the extension of some energy ranges and includes new reactions that are called reference cross sections. Since the effort extends beyond the traditional standards, it is called the neutron data standards evaluation. This international effort has produced new evaluations of the following cross section standards: the H(n,n), Li-6(n,t), B-10(n, alpha), B-10(n,alpha(1)gamma), C-nat(n,n), Au(n,gamma), U-235(n,f) and U-238(n,f). Also in the evaluation process the U-238(n,gamma) and Pu-239(n,f) cross sections that are not standards were evaluated. Evaluations were also obtained for data that are not traditional standards: the Maxwellian spectrum averaged cross section for the Au(n,gamma) cross section at 30 keV; reference cross sections for prompt gamma-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the Cf-252 spontaneous fission neutron spectrum and the U-235 prompt fission neutron spectrum induced by thermal incident neutrons; and the thermal neutron constants. The data and covariance matrices of the uncertainties were obtained directly from the evaluation procedure.
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| 3. |
- Carlson, Allan D., et al.
(författare)
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Results of a New Evaluation of the Neutron Standards
- 2018
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Ingår i: Reactor Dosimetry. - : ASTM International. - 9780803176614 ; , s. 91-104
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Konferensbidrag (refereegranskat)abstract
- An international effort has produced evaluations of the neutron data standards. Evaluations were obtained for the cross section standards: the H(n,n), 6Li(n,t), 10B(n,067), loB(vx), natc(n,n,) Au(n,y), 235U(n,f), and 238U(n,f) reactions. Also in the evaluation process, the 238U(n,y) and 239Pu(n,f) nonstandard cross sections were evaluated. Many of these are dosimetry cross sections. Evaluations were also obtained for data that are not traditional standards: Maxwellian spectrum averaged cross section for the Au(n,y) cross section at 30 keV, reference cross sections for prompt y-ray production in fast neutron-induced reactions, reference cross sections for very high-energy fission cross sections, the 252Cf spontaneous fission neutron spectrum and the 235U thermal fission neutron spectrum, and the thermal constants. The data and covariances were obtained directly from this evaluation procedure as is required by the dosimetry community.
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| 4. |
- Hellesen, Carl, 1980-, et al.
(författare)
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Conceptual design of a BackTOF neutron spectrometer for fuel ion ratio measurements at ITER
- 2017
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 57:6
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a conceptual design of a back scattering neutron time of flight spectrometer (BackTOF) for use at ITER. The proposed BackTOF design aims at fulfilling the requirements set on a neutron spectrometer system to be used for inferring the core fuel ion ratio in a DT plasma. Specifically we have investigated the requirements on the size, energy resolution, count rate capability, efficiency and signal to background ratio. These requirements are a compact size that fits in roughly 1 m3, an energy resolution of 4% or better, a count rate capability of at least 100 kHz, an efficiency of at least 10−5 and a signal to background ratio of 1000 or better.Using a Monte Carlo model of the BackTOF spectrometer we find that the proposed BackTOF design is compact enough to be installed at ITER while being capable of achieving a resolution of about 4% FWHM with a count rate capability of 300 kHz and an efficiency at 1.25 10−3. This is sufficient for achieving the requirements on the fuel ion ratio at ITER. We also demonstrate how data acquisition systems capable of providing both timing and energy information can be used to effectively discriminate random background at high count rates.
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| 5. |
- Marcinkevicius, Benjaminas, et al.
(författare)
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A Thin-foil Proton Recoil spectrometer for DT neutrons using annular silicon detectors
- 2019
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Ingår i: Journal of Instrumentation. - 1748-0221 .- 1748-0221. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The use of Thin-foil Proton Recoil (TPR) spectrometers to measure neutrons from Deuterium-Tritium (DT) fusion plasma has been studied previously and is a well established technique for neutron spectrometry. The study presented here focuses on the optimisation of the TPR spectrometer configurations consisting of Delta E and E silicon detectors. In addition an investigation of the spectrometer's ability to determine fuel ion temperature and fuel ion density ratio in ITER like DT plasmas has been performed. A Python code was developed for the purpose of calculating detection efficiency and energy resolution as a function of several spectrometer geometrical parameters. An optimisation of detection efficiency for selected values of resolution was performed regarding the geometrical spectrometer parameters using a multi-objective optimisation, a.k.a. Pareto plot analysis. Moreover, the influence of detector segmentation on spectrometer energy resolution and efficiency was investigated. The code also produced response functions for the two selected spectrometer configurations. The SPEC code was used to simulate the spectrometer's performance in determining the fuel ion temperature and fuel ion density ratio n(t)/n(d). The results presented include the selected spectrometer configuration with calculated energy resolution and efficiency. For a selected spectrometer resolution of 5% a maximum efficiency of around 0.003% was achieved. Moreover, the detector segmentation allows for a 20% increase in spectrometer efficiency for an energy resolution of 4.3%. The ITER requirements for a 20% accuracy on the n(t)/n(d) ratio determination and 10% on the temperature determination within a 100 ms sampling window can be achieved using a combination of several TPR's of same type, in order to boost efficiency.
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| 6. |
- Marcinkevicius, Benjaminas, et al.
(författare)
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Estimates of TPR spectrometer instrumental signal-to-background ratios and count rate limits for ITER like plasmas
- 2019
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Ingår i: Journal of Instrumentation. - : IOP PUBLISHING LTD. - 1748-0221 .- 1748-0221. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The work presented is a realistic simulation of the response function for a detection efficiency optimized Thin-foil proton recoil (TPR) neutron spectrometer. The TPR spectrometer consists of a thin foil acting as neutron-to-proton converter followed by Delta E-E detectors operating in coincidence mode. In this work, two different spectrometer designs were considered using segmented silicon detectors. Design 1 has slightly better resolution while design 2 is more compact and has higher efficiency. The TPR spectrometer response functions were simulated in the energy range 8-18 MeV in steps of 40 keV for the two designs using the dedicated Monte Carlo code GEANT4. The resulting simulated response functions were broadened using experimentally determined energy resolutions of the detectors, in order to produce more realistic response functions. Using these broadened response functions together with an ITER like neutron spectrum and neutron induced background simulations Delta E/E energy deposition plots were created. The energy-cuts, for 14 MeV neutron signal identification, were applied to the Delta E-E plots leading to an estimate of the expected signal-to-background ratio. In addition, pile-up fraction and maximum expected count rates were estimated. Results show that the Delta E-E energy cuts show a great prospect of increasing the signal-to background ratio for the TPR spectrometer. In addition the TPR spectrometer has energy resolution (FWHM/E) of around 5% for 14 MeV neutrons for both investigated designs. The spectrometer can cope with maximum count rate expected and have a sufficient signal-to-background ratio in the neutron energy range of interest to perform fuel ion ratio measurements. However an increase of acquisition channels would be beneficial to limit the pile-up rate.
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| 7. |
- Marcinkevicius, Benjaminas, et al.
(författare)
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Fuel ion ratio determination using the 14 MeV Tandem neutron spectrometer for JET DTE1 campaign discharges
- 2022
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Ingår i: Fusion engineering and design. - : Elsevier. - 0920-3796 .- 1873-7196. ; 184
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Marcinkevicius, Benjaminas, 1989-
(författare)
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The Thin-foil Proton Recoil neutron spectrometer for DT plasmas
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent advancements in plasma physics are intensifying the demand for advanced diagnostic techniques in fusion research, particularly for the upcoming ITER fusion reactor. The ITER fusion reactor is projected to be ten times more powerful than its predecessors, imposing higher constraints on operational parameters. To meet ITER's requirements, such as the fuel ion ratio nt/nd and fuel ion temperature Ti, a High Resolution Neutron Spectrometer System (HRNS) has been proposed.This thesis focuses on the Thin-foil proton recoil (TPR) spectrometer, an integral part of the HRNS, with an emphasis on its application and validation within the ITER context. The research encompasses two main areas: spectrometer simulations and experimental validation. Through a combination of custom transport code and Geant4 simulations, the study investigates the optimization of the TPR spectrometer's design in terms of efficiency and energy resolution. Additionally, selected design performance under ITER-like conditions has been investigated. These simulations are critical in assessing the spectrometer's capabilities and limitations during operation at ITER. Subsequent experimental validation, conducted using a DT neutron generator and a TPR spectrometer prototype, verified the existing simulation framework in terms of energy resolution and background discrimination methods. We examined a Tandem neutron spectrometer, used in fusion plasma diagnostics at JET to further investigate TPR spectrometer diagnostic possibilities. Tandem spectrometer was operational during JET's first DT campaign, the spectrometer shares the neutron detection principles of the TPR. The fuel ion ratio nt/ntot was determined using the Tandem data together with inputs from PENCIL or TRANSP, for previously not analysed JET discharges. Our findings indicate that estimation of nt/ntot is feasible using either PENCIL or TRANSP. Furthermore, the research demonstrates that TPR based neutron spectrometers can be effectively used in fuel ion ratio determination. In conclusion, this research significantly advances fusion plasma diagnostics. It validates the TPR spectrometer's design in terms of energy resolution and efficiency for ITER, predicting a signal-to-background ratio of approximately 550 and a maximum count rate of 120kHz. The results from the TPR prototype experiment, replicated with the Geant4 simulation, along with comparative analysis with the JET's Tandem spectrometer, highlight the TPR spectrometer's broad applicability in fusion diagnostics, marking a major advancement in the field.
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| 9. |
- Marcinkevicius, Benjaminas, et al.
(författare)
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Thin foil proton recoil spectrometer performance study for application in DT plasma measurements
- 2018
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Ingår i: Review of Scientific Instruments. - : AMER INST PHYSICS. - 0034-6748 .- 1089-7623. ; 89:10
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Tidskriftsartikel (refereegranskat)abstract
- The Thin foil Proton Recoil (TPR) technique has previously been used for deuterium-tritium fusion neutron diagnostics [N. P. Hawkes et al., Rev. Sci. Instrum. 70, 1134 (1999)] and is one of the candidates put forward for use in ITER as part of the high resolution neutron spectrometer (HRNS) system [E. A. Sundden et al., Nucl. Instrum. Methods Phys. Res., Sect. A 701, 62 (2013)]. For ITER, the neutron spectrometer's main purposes are to determine the fuel ion density ratio as well as the ion temperature in DT plasma. This work focuses on testing the capability of a proton telescope detector intended for use as part of the TPR spectrometer. The proton telescope has been tested using proton energies in the range of 3-8 MeV. The experimental results cover energy calibration, resolution estimation, and testing the spectrometer's capability to perform background separation using Delta E - E energy cuts. In addition, spectrometer performance in terms of signal to background ratios for ITER-like DT plasma conditions is estimated using Monte-Carlo simulations. Results show that the TPR-spectrometer geometry dominates in determining the energy resolution and the Delta E - E energy cuts will significantly reduce the background. In addition, the estimated spectrometer count rates in ITER-like conditions fall below 20 kHz per detector segment. Published by AIP Publishing.
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| 10. |
- Marcinkevicius, Benjaminas
(författare)
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Validation of Thin-foil proton recoil neutron spectrometer prototype for application in high yield DT fusion devices
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The use of Thin-foil Proton Recoil (TPR) spectrometers for application in neutron spectroscopy is of high relevance for future fusion devices such as ITER, where neutron spectroscopy will play a crucial role in fuel content monitoring. Existing research based on simulations of the performance of such spectrometers in ITER have demonstrated positive results. However, experimental validation of the simulations would greatly benefit the reliability of these results. In order to fill this gap, in the present study we developed a prototype TPR neutron spectrometer, conducted an experiment using a DT neutron generator and performed simulations using the Geant4 model to replicate the energy spectrum observed by the TPR spectrometer.The prototype of the TPR spectrometer was based on a polyethylene foil used as a neutron-to-proton converter and two double-sided silicon detectors of 0.3 and 1~mm thickness in a ΔE -E configuration. The silicon detectors' energy calibration was performed at Uppsala Tandem laboratory using proton beams. The neutron experiment was performed at Lund University's Applied Nuclear Physics laboratory using a DT neutron generator. The neutron spectrometer was placed in close proximity (within 42 cm) of the source, leading to a high contribution from the scattered neutrons. The Geant4 model of the experiment included a detailed model of the TPR neutron spectrometer, neutron source with surrounding shielding, and a paraffin collimator.The experimental results demonstrated the feasibility of utilizing nuclear reactions measured in silicon detectors, specifically 28Si(n,d) and 28Si(n,α), for energy calibration purposes. The comparative analysis of the measured coincidence energy deposition matches well across the simulations and the experimental data in the energy range above 11~MeV. The mean peak energy and full width at half maximum (FWHM) of the peak are within 150 keV, and within the experimentally determined intrinsic silicon detector energy resolution. Further analysis demonstrates that the ratio between calculated and experimental (C/E) efficiency is 0.8 for energies above 11~MeV. Discrepancies in the measured energy spectrum, particularly at lower energies, indicate the need for a more refined model of the experimental setup and possibly better control of the experimental conditions.Overall, the successful validation of the developed Geant4 simulation model against the experimentally measured energy spectra has increased confidence in the applicability of such simulation results in other devices. Furthermore, the demonstrated energy calibration correction using the nuclear reactions in the silicon detectors highlights new possibilities for neutron spectrometer monitoring during operation at ITER. However, the experiment performed in this study had a significantly higher neutron background rate than anticipated at ITER, and further research is necessary to determine the possibilities of such energy calibration in ITER.
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