| 1. |
- Cazzaniga, C., et al.
(författare)
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Single crystal diamond detector measurements of deuterium-deuterium and deuterium-tritium neutrons in Joint European Torus fusion plasmas
- 2014
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 85:4, s. 043506-
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Tidskriftsartikel (refereegranskat)abstract
- First simultaneous measurements of deuterium-deuterium (DD) and deuterium-tritium neutrons from deuterium plasmas using a Single crystal Diamond Detector are presented in this paper. The measurements were performed at JET with a dedicated electronic chain that combined high count rate capabilities and high energy resolution. The deposited energy spectrum from DD neutrons was successfully reproduced by means of Monte Carlo calculations of the detector response function and simulations of neutron emission from the plasma, including background contributions. The reported results are of relevance for the development of compact neutron detectors with spectroscopy capabilities for installation in camera systems of present and future high power fusion experiments.
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| 2. |
- Giacomelli, L., et al.
(författare)
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Neutron emission spectroscopy of DT plasmas at enhanced energy resolution with diamond detectors
- 2016
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Ingår i: Review of Scientific Instruments. - : AMER INST PHYSICS. - 0034-6748 .- 1089-7623. ; 87:11
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Tidskriftsartikel (refereegranskat)abstract
- This work presents measurements done at the Peking University Van de Graaff neutron source of the response of single crystal synthetic diamond (SD) detectors to quasi-monoenergetic neutrons of 14-20 MeV. The results show an energy resolution of 1% for incoming 20 MeV neutrons, which, together with 1% detection efficiency, opens up to new prospects for fast ion physics studies in high performance nuclear fusion devices such as SD neutron spectrometry of deuterium-tritium plasmas heated by neutral beam injection.
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| 3. |
- Giacomelli, L., et al.
(författare)
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Neutron emission spectroscopy results for internal transport barrier and mode conversion ion cyclotron resonance heating experiments at JET
- 2008
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 79:10, s. 10E514-
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Tidskriftsartikel (refereegranskat)abstract
- The effect of ion cyclotron resonance heating (ICRH) on ((3)He)D plasmas at JET was studied with the time of flight optimized rate (TOFOR) spectrometer dedicated to 2.5 MeV dd neutron measurements. In internal transport barrier (ITB) plasma experiments with large (3)He concentrations (X((3)He)>15%) an increase in neutron yield was observed after the ITB disappeared but with the auxiliary neutral beam injection and ICRH power still applied. The analysis of the TOFOR data revealed the formation of a high energy (fast) D population in this regime. The results were compared to other mode conversion experiments with similar X((3)He) but slightly different heating conditions. In this study we report on the high energy neutron tails originating from the fast D ions and their correlation with X((3)He) and discuss the light it can shed on ICRH-plasma power coupling mechanisms.
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| 4. |
- Giacomelli, L., et al.
(författare)
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Tomographic analysis of neutron and gamma pulse shape distributions from liquid scintillation detectors at Joint European Torus
- 2014
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 85:2, s. 023505-
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Tidskriftsartikel (refereegranskat)abstract
- The Joint European Torus (JET, Culham, UK) is the largest tokamak in the world devoted to nuclear fusion experiments of magnetic confined Deuterium (D)/Deuterium-Tritium (DT) plasmas. Neutrons produced in these plasmas are measured using various types of neutron detectors and spectrometers. Two of these instruments on JET make use of organic liquid scintillator detectors. The neutron emission profile monitor implements 19 liquid scintillation counters to detect the 2.45 MeV neutron emission from D plasmas. A new compact neutron spectrometer is operational at JET since 2010 to measure the neutron energy spectra from both D and DT plasmas. Liquid scintillation detectors are sensitive to both neutron and gamma radiation but give light responses of different decay time such that pulse shape discrimination techniques can be applied to identify the neutron contribution of interest from the data. The most common technique consists of integrating the radiation pulse shapes within different ranges of their rising and/or trailing edges. In this article, a step forward in this type of analysis is presented. The method applies a tomographic analysis of the 3-dimensional neutron and gamma pulse shape and pulse height distribution data obtained from liquid scintillation detectors such that n/gamma discrimination can be improved to lower energies and additional information can be gained on neutron contributions to the gamma events and vice versa.
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| 5. |
- Gorini, G, et al.
(författare)
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Relationship between neutron yield rate of tokamak plasmas and spectrometer measured flux for different sight lines
- 2011
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:3, s. 033507-
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Tidskriftsartikel (refereegranskat)abstract
- A parametric relationship between total neutron yield rate and collimated fluxes related to the brightness (B) of plasma chords (lambda) is developed for different emissivity distributions of tokamak plasmas. Specifically, the brightness was expressed as a function of chord coordinates of radial position using a simple model for the emissivity profiles of width parameter w. The functional brightness dependence B(lambda,w) was calculated to examine the relationship between measured flux and deduced yield rate, and its plasma profile dependence. The results were used to determine the chord range of minimum profile sensitivity in order to identify the preferred collimator sight for the determination of yield rate from neutron emission spectroscopy (YNES) measurements. The YNES method is discussed in comparison to conventional methods to determine the total neutron yield rates and related plasma fusion power relying on uncollimated flux measurements and a different calibration base for the flux-yield relationship. The results have a special bearing for tokamaks operating with both deuterium and deuterium-tritium plasmas and future high power machines such as for ITER, DEMO, and IGNITOR.
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| 6. |
- Hellesen, Carl, et al.
(författare)
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Validation of TRANSP Simulations Using Neutron emission Spectroscopy with Dual Sight Lines
- 2008
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 79:10, s. 10E510-
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Tidskriftsartikel (refereegranskat)abstract
- A method to generate modeled neutron spectra from bulk and fast ion distributions simulated by TRANSP has been developed. In this paper, modeled data generated from fuel ion distrubutions modeled with TRANSP is compared to measured data from two neutron spectrometers with different lines of sight; TOFOR with a radial one and the MPRu with a tangential one. The information obtained from the analysis of the measured neutron spectra such as the relative intensity of the emission from different ion populations places additional constraints on the simulation and can be used to adjust the parameters of the simulation.
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| 7. |
- Johnson, M. Gatu, et al.
(författare)
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Neutron spectrometry of JET discharges with ICRH-acceleration of helium beam ions
- 2010
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 81:10, s. 10D336-
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Tidskriftsartikel (refereegranskat)abstract
- Recent experiments at JET aimed at producing He-4 ions in the MeV range through third harmonic ion cyclotron resonance heating (ICRH) acceleration of He-4 beams in a He-4 dominated plasma. MeV range D was also present through parasitic ICRH absorption on residual D. In this contribution, we analyze TOFOR neutron spectrometer data from these experiments. A consistent description of the data is obtained with d(d, n)(3) He and Be-9(alpha, n)C-12 neutron components calculated using Stix distributions for the fast D and He-4, taking finite Larmor radius effects into account and with a ICRH power partition of P-D(RF) = 0.01 X P-4He(RF), in agreement with TOMCAT simulations.
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| 8. |
- Korsholm, S. B., et al.
(författare)
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Development of novel fuel ion ratio diagnostic techniques
- 2010
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 81:10, s. 10D323-
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Tidskriftsartikel (refereegranskat)abstract
- To overcome the challenge of measuring the fuel ion ratio in the core (rho<0.3) of ITER, a coordinated effort aiming at developing diagnostic techniques has been initiated. The investigated techniques are novel uses or further development of existing methods such as charge exchange recombination spectrometry, neutron spectrometry, and collective Thomson scattering. An overview of the work on the three diagnostic techniques is presented.
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| 9. |
- Nocente, M., et al.
(författare)
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Fast ion energy distribution from third harmonic radio frequency heating measured with a single crystal diamond detector at the Joint European Torus
- 2015
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Ingår i: Review of Scientific Instruments. - : AMER INST PHYSICS. - 0034-6748 .- 1089-7623. ; 86:10
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Tidskriftsartikel (refereegranskat)abstract
- Neutron spectroscopy measurements with a single crystal diamond detector have been carried out at JET, for the first time in an experiment aimed at accelerating deuterons to MeV energies with radio frequency heating at the third harmonic. Data are interpreted by means of the expected response function of the detector and are used to extract parameters of the highly non-Maxwellian distribution function generated in this scenario. A comparison with observations using a time of flight and liquid scintillator neutron spectrometers is also presented. The results demonstrate the capability of diamond detectors to contribute to fast ion physics studies at JET and are of more general relevance in view of the application of such detectors for spectroscopy measurements in the neutron camera of next step tokamak devices.
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| 10. |
- Nocente, M., et al.
(författare)
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Fusion product measurements by nuclear diagnostics in the Joint European Torus deuterium-tritium 2 campaign (invited)
- 2022
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 93:9
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Tidskriftsartikel (refereegranskat)abstract
- A new deuterium-tritium experimental, DTE2, campaign has been conducted at the Joint European Torus (JET) between August 2021 and late December 2021. Motivated by significant enhancements in the past decade at JET, such as the ITER-like wall and enhanced auxiliary heating power, the campaign achieved a new fusion energy world record and performed a broad range of fundamental experiments to inform ITER physics scenarios and operations. New capabilities in the area of fusion product measurements by nuclear diagnostics were available as a result of a decade long enhancement program. These have been tested for the first time in DTE2 and a concise overview is provided here. Confined alpha particle measurements by gamma-ray spectroscopy were successfully demonstrated, albeit with limitations at neutron rates higher than some 10(17) n/s. High resolution neutron spectroscopy measurements with the magnetic proton recoil instrument were complemented by novel data from a set of synthetic diamond detectors, which enabled studies of the supra-thermal contributions to the neutron emission. In the area of escaping fast ion diagnostics, a lost fast ion detector and a set of Faraday cups made it possible to determine information on the velocity space and poloidal distribution of the lost alpha particles for the first time. This extensive set of data provides unique information for fundamental physics studies and validation of the numerical models, which are key to inform the physics and scenarios of ITER. Published under an exclusive license by AIP Publishing.
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