Fuel ion ratio determination in NBI heated deuterium tritium fusion plasmas at JET using neutron emission spectrometry

Hellesen, C.; Eriksson, J.; Binda, Federico; Conroy, S.; Ericsson, Göran; Hjalmarsson, Anders; Skiba, Mateusz; Weiszflog, M.; Contributors, Jet‐Efda

doi:10.1088/0029-5515/55/2/023005

Cited by 20 publications

(22 citation statements)

References 17 publications

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“…The HRNS is considered the primary diagnostic for performing this measurement. As discussed in [47], the determination of n T /n D requires that thermonuclear and beam-target neutron emission components can be separated from each other in the measured neutron spectrum. I.e., even though the n T /n D determination is not a fast ion measurement per se, it still requires that the 1 MeV beam deuterons can be accurately measured.…”

Section: Outlook Towards Itermentioning

confidence: 99%

Measuring fast ions in fusion plasmas with neutron diagnostics at JET

Eriksson

Hellesen

Binda

et al. 2018

Plasma Phys. Control. Fusion

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Fast ions in fusion plasmas often leave characteristic signatures in the neutron emission from the plasma. In this paper, we show how neutron measurements can be used to study fast ions and give examples of physics results obtained on present day tokamaks. The focus is on measurements with dedicated neutron spectrometers and with compact neutron detectors used in each channel of neutron profile monitors. A measured neutron spectrum can be analyzed in several different ways, depending on the physics scenario under consideration. Gross features of a fast ion energy distribution can be studied by applying suitably chosen thresholds to the measured spectrum, thus probing ions with different energies. With this technique it is possible to study the interaction between fast ions and MHD activity, such as toroidal Alfvén eigenmodes and sawtooth instabilities. Quantitative comparisons with modeling can be performed by a direct computation of the neutron emission expected from a given fast ion distribution. Within this framework it is also possible to determine physics parameters, such as the supra-thermal fraction of the neutron emission, by fitting model parameters to the data. A detailed, model-independent estimate of the fast ion distribution can be obtained by analyzing the data in terms of velocity space weight functions. Using this method, fast ion distributions can be resolved in both energy and pitch by combining neutron and gamma-ray measurements obtained along several different sightlines. Fast ion measurements of the type described in this paper will also be possible at ITER, provided that the spectrometers have the dynamic range required to resolve the fast ion spectral features in the presence of the dominating thermonuclear neutron emission. A dedicated high-resolution neutron spectrometer has been designed for this purpose.

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Section: Outlook Towards Itermentioning

confidence: 99%

Measuring fast ions in fusion plasmas with neutron diagnostics at JET

Eriksson

Hellesen

Binda

et al. 2018

Plasma Phys. Control. Fusion

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“…They can be used to extract essential parameters for machine control, such as the fuel ion temperature, 1 the thermal/non-thermal components of the neutron emission, 2,3 and the fuel ion ratio. 4 More recently, they have contributed to fundamental studies on the physics of suprathermal ions in thermonuclear plasmas, mostly by detailed measurements of the distribution function of the energetic ions [5][6][7] and their effects on the plasma stability. 8,9 Advanced neutron spectroscopy measurements are nowadays performed along a single, collimated line of sight by means of dedicated, non-compact detectors, based on the time of flight technique [10][11][12] for deuterium-deuterium (dd) fusion neutrons and on proton recoil for deuterium-tritium (dt).…”

Section: Introductionmentioning

confidence: 99%

Fast ion energy distribution from third harmonic radio frequency heating measured with a single crystal diamond detector at the Joint European Torus

Nocente

Cazzaniga

Tardocchi

et al. 2015

Review of Scientific Instruments

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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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“…These results demonstrate the capability of SCD to determine the beam composition in a mixed DT beam and could be applied on the neutral beams injected in thermonuclear fusion experiments. This was demonstrated in an earlier work [18], where the main features of the neutron spectrum have been observed on the JET tokamak with a mixed D/T beam used to heat the plasma.…”

Section: Analysis Of the Beam Compositionmentioning

confidence: 68%

Neutron spectroscopy measurements of 14 MeV neutrons at unprecedented energy resolution and implications for deuterium–tritium fusion plasma diagnostics

Rigamonti

Giacomelli

Gorini

et al. 2018

Meas. Sci. Technol.

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An accurate calibration of the JET neutron diagnostics with a 14 MeV neutron generator was performed in the first half of 2017 in order to provide a reliable measurement of the fusion power during the next JET deuterium-tritium (DT) campaign. In order to meet the target accuracy, the chosen neutron generator has been fully characterized at the Neutron Metrology Laboratory of the National Physical Laboratory (NPL), Teddington, United Kingdom. The present paper describes the measurements of the neutron energy spectra obtained using a highresolution single-crystal diamond detector (SCD). The measurements, together with a new neutron source routine 'ad hoc' developed for the MCNP code, allowed the complex features of the neutron energy spectra resulting from the mixed D/T beam ions interacting with the T/D target nuclei to be resolved for the first time. From the spectral analysis a quantitative estimation of the beam ion composition has been made. The unprecedented intrinsic energy resolution (<1% full width at half maximum (FWHM) at 14 MeV) of diamond detectors opens up new prospects for diagnosing DT plasmas, such as, for instance, the possibility to study non-classical slowing down of the beam ions by neutron spectroscopy on ITER.

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Fuel ion ratio determination in NBI heated deuterium tritium fusion plasmas at JET using neutron emission spectrometry

Cited by 20 publications

References 17 publications

Measuring fast ions in fusion plasmas with neutron diagnostics at JET

Measuring fast ions in fusion plasmas with neutron diagnostics at JET

Fast ion energy distribution from third harmonic radio frequency heating measured with a single crystal diamond detector at the Joint European Torus

Neutron spectroscopy measurements of 14 MeV neutrons at unprecedented energy resolution and implications for deuterium–tritium fusion plasma diagnostics

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