The upgraded JET gamma-ray cameras based on high resolution/high count rate compact spectrometers

Abstract

The JET gamma-ray cameras have been recently upgraded within the gamma-ray camera upgrade project in support of development of JET high performance deuterium plasma scenarios and in preparation of deuterium-tritium experiments. New, dedicated detectors based on a LaBr3 crystal and silicon photo-multipliers have been developed and replaced pre-existing CsI detectors in all 19 channels. The new instrument gives opportunity of making two-dimensional gamma-ray measurements with a counting rate capability exceeding 1 MCounts/s (MCps) and energy resolution better than 5% at 1.1 MeV. The upgrade is of relevance for fast ion and runaway electron physics studies in high performance deuterium discharges and also in plasmas with tritium at neutron yields in the range up to about 5 × 1017 n/s.

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

“…Otherwise, many of the observed lines would not be measured according to calculations. Another opportunity provided by GRS is the possibility to make spatially resolved images of the gamma-ray emission, which is obtained by observing the plasma along multiple lines of sight at the same time [18,30,10]. This is useful to tell the FI profile in the poloidal cross section and to observe how this changes in response to the external actuators.…”

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

“…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). The GC determines the profile of fast ions in general, including α particles in DT, by detecting gamma-ray emission from characteristic nuclear reactions along a set of horizontal and vertical lines of sight a) massimo.nocente@mib.infn.it b) See the author list of E. Joffrin et al 2019 Nucl.…”

First spatially resolved measurements of the D–3He α-particle source with the upgraded JET gamma-ray camera

“…However, the online version of record will be different from this version once it has been copyedited and typeset. (SiPM) have been developed and installed in the camera 4 : the new system exhibits an energy resolution better than 3% at 4.44 MeV and a counting rate capability in excess of 1 MCps. SiPMs are compact (12x12 mm 2 and 2 mm thick) and insensitive to the magnetic field.…”

“…In view of the upcoming JET deuterium-tritium campaign 3 , the system has undergone a major upgrade [4][5][6] , within the EU-ROFUSION enhancement program by the Gamma-ray Camera Upgrade (GCU) project, to meet the demanding conditions for measurements in plasmas at different tritium concentrations. The DT campaign will allow the study of the dynamics of fusion born alpha-particles, which is also of interest for ITER 7 , thus the detection of the 4.44 MeV photons emitted in α( 9 Be, n) 12 C * reactions under high neutron fluxes will be of crucial importance.…”