MeV range particle physics studies in tokamak plasmas using gamma-ray spectroscopy

Abstract

Gamma-ray spectroscopy (GRS) has become an established technique to determine properties of the distribution function of the energetic particles in the MeV range, which are fast ions from heating and fusion reactions or runaway electrons born in disruptions.In this paper we present a selection of recent results where GRS is key to investigate the physics of MeV range particles. These range from radio-frequency heating experiments, where theoretical models can be tested with an unprecedented degree of accuracy, to disruption mitigation studies, where GRS sheds light on the effect of the actuators on the runaway electron velocity space. We further discuss the unique observational capabilities offered by the technique in deuterium-tritium plasmas, particularly with regard to the inference of the energyand pitch-resolved distribution function of the α particles born from fusion reactions in the plasma core.

Plasma heating and generation of energetic D ions with the 3-ion ICRF + NBI scenario in mixed H-D plasmas at JET-ILW

“…Note that the inferred value is close to the effective D ion tail temperature predicted by PION and TRANSP simulations [16,34]. Another independent confirmation for the presence of high-energy D ions generated with ICRF is provided by gamma-ray emission spectroscopy [35]. As a result of nuclear reactions between fast D ions and intrinsic 9 Be impurities, heavy nuclei in an excited state, 10 Be* and 10 B*, are produced [28].…”

Fast-ion velocity-space tomography using slowing-down regularization in EAST plasmas with co- and counter-current neutral beam injection

“…geometric consideration of neutral beam injection, is likely to, furthermore, enable velocity-space reconstructions from single-view measurements, which has until now been unattainable. Examples of systems that are likely to benefit from the restricted basis function approach are FIDA measurements at MAST [14], TCV [51] and NSTX [52,53], CTS measurements at Wendelstein 7-X [54] and LHD [55], as well as NES and GRS measurements at JET [56,57].…”

A new tangential gamma-ray spectrometer for fast ion measurements in deuterium and deuterium–tritium plasmas of the Joint European Torus

“…From the diagnostics side, a number of enhancements has been conducted to improve the alpha particle observational capabilities of JET 3 , particularly as far as gamma-ray spectrometry is concerned. Here the main interest is in the detection of the 4.44 MeV line from the α + 9 Be → n + 12 C * reaction 4 , as this emission provides information on the alpha particle energy distribution, as well as its profile 5 . The main instruments developed for this scope are a gamma-ray camera (GC) 6,7 and two set of gamma-ray spectrometers (GRS), one vertical (V-GRS) and one tangential (T-GRS).…”