Investigating the performance of an ion luminescence probe as a multichannel fast-ion energy spectrometer using pulse height analysis

Zurro, B.; Baciero, A.; Jiménez-Rey, D.; Rodríguez-Barquero, L.; Crespo, M.T.

doi:10.1063/1.4733572

Cited by 4 publications

(7 citation statements)

References 22 publications

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“…The tuning consists of finding an optimal location for the detector where the pulse pile-up effects are negligible and selecting the amplifier gain to avoid pulse saturation, within the analogue to digital converter range, during the NBI phase, but having sufficient pulse amplitude, well above noise, during the ECRH phase. For this purpose the LP is operated, for the first time in this range of energies, as a multichannel fast-ion energy spectrometer using the pulse height analysis [8].…”

Section: Experimental Set-upsmentioning

confidence: 99%

“…More recently we have added to passive spectroscopic techniques a luminescent probe (LP) [7] to detect those suprathermal ions escaping from the confinement region, in both cases with time resolution and with additional spatial resolution in the first case. The excellent sensitivity and operation of the LP in a height pulse analysis regime, and data processed by an ad hoc digital pulse algorithm, has enabled the determination of the ion distribution function in ECRH and NBI regimes [8]. In this work we exploit these two complementary approaches to extract information on the suprathermal ion confinement and about their spatial and time properties evolution using specific TJ-II scenarios and selected discharges within them.…”

Section: Introductionmentioning

confidence: 99%

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Suprathermal ion studies in ECRH and NBI phases of the TJ-II stellarator

Zurro¹,

Baciero²,

Tribaldos

et al. 2013

Nucl. Fusion

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The goal of this work is to study the empirical behaviour of suprathermal ions in the electron cyclotron resonance heating (ECRH) and neutral-beam injection (NBI) phases of the TJ-II stellarator. Our approach combines passive emission spectroscopy, which detects confined suprathermal ions with energies up to hundreds of electronvolts, and a luminescent probe operated as a multichannel fast-ion energy spectrometer using pulse height analysis, which detects suprathermal ions with energies ⩾1 keV that escape from the plasma. We will present data taken from density and power scans of TJ-II ECRH plasmas and the spatial and time response of suprathermal protons and impurities in both scenarios. The comparative behaviour between the suprathermal ions present in the plasma and those escaping ions may shed some light on the physical mechanisms responsible for the generation and confinement of these ions.

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Section: Experimental Set-upsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Suprathermal ion studies in ECRH and NBI phases of the TJ-II stellarator

Zurro¹,

Baciero²,

Tribaldos

et al. 2013

Nucl. Fusion

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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%

“…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. This permits the determination of the ion energy distribution function, f ( W ), as well as the ion count rate within energy and time windows.…”

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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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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“…It is used to detect and measure properties of the suprathermal ions that escape from plasmas generated in this device by electron cyclotron resonance heating (ECRH) and/or neutral beam injection (NBI) heating [13]. Originally, it was prepared to work in an ion counting mode [14] where pulse amplitude, proportional to the ion energy, permits determination of the ion energy distribution function, f (W), as well as the ion count rate within an energy and time window. This permits ion counting with energy discrimination and tracking the count rate evolution along TJ-II discharges.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the role of electron cyclotron resonance heating and magnetic configuration on the suprathermal ion population in the stellarator TJ-II using a luminescent probe

Martínez

Zurro

Baciero

et al. 2018

Plasma Phys. Control. Fusion

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Numerous observation exist of a population of high energetic ions with energies well above the corresponding thermal values in plasmas generated by electron cyclotron resonance (ECR) heating in TJ-II stellarator and in other magnetically confined plasmas devices. In this work we study the impact of ECR heating different conditions (positions and powers) on fast ions escaping from plasmas in the TJ-II stellarator. For this study, an ion luminescent probe operated in counting mode is used to measure the energy distribution of suprathermal ions, in the range from 1 to 30 keV. It is observed that some suprathermal ions characteristics (such as temperature, particle and energy fluxes) are related directly with the gyrotron power and focus position of the heating beam in the plasma. Moreover, it is found that suprathermal ion characteristics vary during a magnetic configuration scan (performed along a single discharge). By investigating the suprathermal ions escaping from plasmas generated using two gyrotrons, one with fixed power and the other modulated (on/off) at low frequency (10 Hz), the de-confinement time of the suprathermal ions can be measured, which is of the order of a few milliseconds (<4 ms). A model that uses a zero-dimensional power balance is used to understand the de-confinement times in terms of the interaction of suprathermal ions and plasma components. This model also can be used to interpret experimental results of energy loss due to suprathermal ions. Finally, observations of increases (peaks) in the population of escaping suprathermal ions, which are well localized at discrete energies, is documented, these peaks being observed in the energy distributions along a discharge.

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Investigating the performance of an ion luminescence probe as a multichannel fast-ion energy spectrometer using pulse height analysis

Cited by 4 publications

References 22 publications

Suprathermal ion studies in ECRH and NBI phases of the TJ-II stellarator

Suprathermal ion studies in ECRH and NBI phases of the TJ-II stellarator

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

Investigation of the role of electron cyclotron resonance heating and magnetic configuration on the suprathermal ion population in the stellarator TJ-II using a luminescent probe

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