Improvements to the Faraday cup fast ion loss detector and magnetohydrodynamic induced fast ion loss measurements in Joint European Torus plasmas

Abstract

Upgrades to electronic hardware and detector design have been made to the JET thin-foil Faraday cup fast ion loss detector [Darrow et al., Rev. Sci. Instrum. 75, 3566 (2004)] in anticipation of the upcoming deuterium–tritium (DT) campaign. An improved foil stack design has been implemented, which greatly reduces the number of foil-to-foil shorts, and triaxial cabling has mitigated ambient noise pickup. Initial tests of 200 kHz digitizers, as opposed to the original 5 kHz digitizers, have provided enhanced analysis techniques and direct coherence measurements of fast ion losses with magnetohydrodynamic activity. We present recent loss measurements in JET deuterium plasmas correlated with kink modes, fishbone modes, edge-localized modes, and sawteeth. Sources of systematic noise are discussed with emphasis on capacitive plasma pickup. Overall, the system upgrades have established a diagnostic capable of recording alpha particle losses due to a wide variety of resonant fast ion transport mechanisms to be used in future DT-experiments and modeling efforts.

Numerical studies on saturated kink and sawtooth induced fast ion transport in JET ITER-like plasmas

“…This is consistent with the results presented in figure 3 and the evolving neutron rate which is dominated by beam-thermal interactions [33]. Analysis of Faraday cup fast ion loss array [21] signals, which are sensitive to fusion product and RF-heated beam losses, did not reveal any sawtooth induced losses above the detector noise floor. These loss measurements suggest that the sawtooth may only induce weak losses and be more likely to redistribute the fast ion population.…”

“…The two instabilities provide the means for both resonant and non-resonant transport for analysis. Discussed extensively in reference [6], the saturated kink modes give rise to measureable fast ion losses in JET's Faraday cup fast ion loss detector [21] and scintillator probe [22].…”

Simulating energetic particle losses in JET plasmas with a reverse integration biasing scheme

“…In short, the deeper the ion deposition, the higher the energy. Reference [22] provides a complete table of the resolvable energy range per foil per ion species.…”

“…Synthetic loss detectors have been produced to compare numerically modeled losses to experimental measurements [14][15][16][17][18]. It has been readily observed that fast ion loss detector (FILD) signals correlate with many loss mechanisms of interest [19][20][21][22][23]. Thus, it is possible to form a fully integrated energetic particle transport model which can then be quantitatively corroborated against experimental measurement.…”

Joint meeting of 9th Asia Pacific-Transport Working Group (APTWG) & EU-US Transport Task Force (TTF) workshop

“…The TRANSP/NUBEAM code provides a time-dependent model for the equilibrium and fast ion distribution for use in the ORBIT-kick model, which calculates the fast ion transport associated with a supplied EP instability. Furthermore, the geometry for a series of thin-foil Faraday cup fast ion loss detectors, capable of spatial and energy-resolved loss measurements [74] was installed in the code to produce synthetic loss signals for comparison to the experiment. Perturbatively induced losses can then be tracked to the detector geometry to produce synthetic loss signals.…”