| 1. |
- 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. ; 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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| 2. |
- 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. ; 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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| 3. |
- Scholz, Marek, et al.
(författare)
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Conceptual design of the high resolution neutron spectrometer for ITER
- 2019
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Ingår i: Nuclear Fusion. - 0029-5515 .- 1741-4326. ; 59:6
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Tidskriftsartikel (refereegranskat)abstract
- A high resolution neutron spectrometer (HRNS) system has been designed as a neutron diagnostic tool for ITER. The HRNS is dedicated to measurements of time resolved neutron energy spectra for both deuterium and deuterium-tritium (DT) plasmas. The main function of the HRNS is to determine the fuel ion ratio n(t)/n(d) in the plasma core with 20% uncertainty and a time resolution of 100ms for a range of ITER operating scenarios from 0.5 MW to 500 MW in fusion power. Moreover, neutron spectroscopy measurements should also be possible in the initial deuterium phase of ITER experiments. A supplementary function of the HRNS is to provide information on the fuel ion temperature. Furthermore, the HRNS can be used as an additional line-of-sight (LOS) for the radial neutron camera. To meet these requirements, a set of four spectrometers positioned after each other along a single LOS has been designed. The detector techniques employed include a thin foil proton recoil spectrometer (TPR), a neutron diamond detector (NDD), a back-scattering time-of-flight system (bToF) and a forward timeof-flight system (fToF). The TPR system, positioned closest to the plasma, provides data at high fusion powers. For plasma conditions producing intermediate fusion power two neutron spectrometers are installed: NDD and bToF. The NDD is installed as the second instrument along the HRNS LOS after the TPR. The fToF spectrometer is dedicated for low tritium densities and pure deuterium operation. The paper summarizes the current state of the art of neutron spectroscopy useful in plasma diagnostics and the possibility of installing a dedicated HRNS for ITER in the designated diagnostic port. We conclude that the proposed HRNS system can fulfil the ITER measurement requirements over a broad range of plasma operational scenarios, including full power DT, start-up, ramp-down and pure D operations.
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