A flexible luminescent probe to monitor fast ion losses at the edge of the TJ-II stellarator

Jiménez-Rey, D.; Zurro, B.; Guasp, J.; Liniers, M.; Baciero, A.; García-Muñoz, M.; Fernández, Á.; Garcı́a, Gustavo; Rodríguez-Barquero, L.; Fontdecaba, J. M.

doi:10.1063/1.2979013

Cited by 25 publications

(21 citation statements)

References 15 publications

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“…Correct operation of the LP in the former mode was demonstrated previously in ECRH and NBI plasmas of TJ‐II by comparison with spectroscopy methods . Finally, this LP was previously operated with a SrGa2S4:Eu phosphor screen (TG‐Green, decay time = 540 ns) . This allowed the study of energy distributions in the ms range .…”

Section: Introductionmentioning

confidence: 82%

“…Its operation principle is based on the detection of ionoluminescence from a granular luminescent screen, which occurs when ions impact this screen. It is used to detect and measure properties of the fast ions that escape from plasmas generated in this device during the electron cyclotron resonance heating (ECRH) and/or NBI heating phases . It is prepared to work in an ion counting mode where pulse amplitude is proportional to ion energy.…”

Section: Introductionmentioning

confidence: 99%

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Discrete fast‐ion detection with energy discrimination in plasmas having edge‐localized mode‐like instabilities in the stellarator TJ‐II

Martínez

Zurro²,

Baciero³

et al. 2018

Contributions to Plasma Physics

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The existence of a population of ions, with energies well above the corresponding thermal values, in plasmas heated by neutral beam injection (NBI) in the stellarator TJ-II and in other magnetically confined plasmas devices is well known. Moreover, during the NBI phase of the TJ-II, edge-localized mode-like (ELM-like) instabilities often appear. This work studies the relationship between fast ions escaping from TJ-II plasmas and such ELM-like events. For this, an ion luminescent probe (LP), operated with a fast scintillator (decay time = 27 ns) and high-speed conditioning electronics (100 MHz), is used to measure, without pile-up effects, the energy distribution of suprathermal ions across the energy range, from 1 to 30 keV. It is found that the LP detects suprathermal ion populations that can be related to ELM-like events whose temperatures oscillate between 0.5 and 3 keV and that can be distinguished in a spectrogram of the LP response as an increase in frequencies from 15 to 150 kHz. Finally, observations of substructures within ELM-likes events, consisting of bursts of ions, with times between 5 and 15 μs are also reported. Such substructures have been observed previously in both tokamaks and stellarators in ion saturation current, high-speed camera images, etc. However, understanding the fast-ion component can provide new and relevant information about the behaviour of ions.

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Section: Introductionmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Discrete fast‐ion detection with energy discrimination in plasmas having edge‐localized mode‐like instabilities in the stellarator TJ‐II

Martínez

Zurro²,

Baciero³

et al. 2018

Contributions to Plasma Physics

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“…In particular, with respect to the last item, it was seen that the loss rate was altered during ECH, which is known to affect the radial electric field structure. Measurements on TJ-II [11] also indicate a change in beam ion loss rate during ECH. Given that the dominant feature of the loss signal is the loss of ions at the pitch angle of transition orbits, it seems possible that one or several of the processes listed above might move passing particles (presumably the dominant population of particles given the injection angle under normal conditions) onto transition orbits.…”

Section: Discussionmentioning

confidence: 99%

“…[8][9][10] Similarly, characteristics of fast ion loss from the TJ-II stellarator have been reported in Ref. 11. A description of fast ion losses from the W7-AS stellarator is contained in Ref.…”

Section: Beam Ion Loss Diagnosticmentioning

confidence: 99%

Measurements of beam ion loss from the Compact Helical System

Darrow¹,

Isobe²,

Kondo³

et al. 2010

Nucl. Fusion

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Beam ion loss from the Compact Helical System (CHS) has been measured with a scintillator-type probe. The total loss to the probe, and the pitch angle and gyroradius distributions of that loss, have been measured as various plasma parameters were scanned. Three classes of beam ion loss were observed at the probe position: passing ions with pitch angles within 10° of those of transition orbits, ions on transition orbits, and ions on trapped orbits, typically 15° or more from transition orbits. Some orbit calculations in this geometry have been performed in order to understand the characteristics of the loss. Simulation of the detector signal based upon the following of orbits from realistic beam deposition profiles is not able to reproduce the pitch angle distribution of the losses measured. Consequently it is inferred that internal plasma processes, whether magnetohydrodynamic modes, radial electric fields, or plasma turbulence, move previously confined beam ions to transition orbits, resulting in their loss.

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“…8 Now many devices are equipped with various forms of fast ion loss detectors with different names (e.g., FILD, FIL, SLIP, SP, sFILP, etc.). [9][10][11][12][13][14][15][16] ("FILD" will be used in the rest of the paper.) A common fast ion loss detector is a scintillator-based detector with a charge-coupled device (CCD) camera and/or photomultiplier (PMT) detection system.…”

Section: Principle Of Libpmentioning

confidence: 99%

Using neutral beams as a light ion beam probe (invited)

Chen

Heidbrink

Zeeland

et al. 2014

Review of Scientific Instruments

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By arranging the particle first banana orbits to pass near a distant detector, the light ion beam probe (LIBP) utilizes orbital deflection to probe internal fields and field fluctuations. The LIBP technique takes advantage of (1) the in situ, known source of fast ions created by beam-injected neutral particles that naturally ionize near the plasma edge and (2) various commonly available diagnostics as its detector. These born trapped particles can traverse the plasma core on their inner banana leg before returning to the plasma edge. Orbital displacements (the forces on fast ions) caused by internal instabilities or edge perturbing fields appear as modulated signal at an edge detector. Adjustments in the q-profile and plasma shape that determine the first orbit, as well as the relative position of the source and detector, enable studies under a wide variety of plasma conditions. This diagnostic technique can be used to probe the impact on fast ions of various instabilities, e.g., Alfvén eigenmodes (AEs) and neoclassical tearing modes, and of externally imposed 3D fields, e.g., magnetic perturbations. To date, displacements by AEs and by externally applied resonant magnetic perturbation fields have been measured using a fast ion loss detector. Comparisons with simulations are shown. In addition, nonlinear interactions between fast ions and independent AE waves are revealed by this technique.

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A flexible luminescent probe to monitor fast ion losses at the edge of the TJ-II stellarator

Cited by 25 publications

References 15 publications

Discrete fast‐ion detection with energy discrimination in plasmas having edge‐localized mode‐like instabilities in the stellarator TJ‐II

Discrete fast‐ion detection with energy discrimination in plasmas having edge‐localized mode‐like instabilities in the stellarator TJ‐II

Measurements of beam ion loss from the Compact Helical System

Using neutral beams as a light ion beam probe (invited)

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