Ion temperature measurements in the tokamak scrape-off layer with high temporal resolution

Adámek, Jiřı́; Cipciar, D.; Devitre, A.; Horáček, J.; Cavalier, J.; Komm, M.; Krbec, J.; Tichý, M.; Trunec, David; Böhm, P.; Pánek, R.

doi:10.1088/1741-4326/abd41d

Cited by 6 publications

(12 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, it is worth noting that the most important aspect of the system is its high versatility, so as to have the possibility to adopt the most suitable set-up. As matter of example the system would allow to verify temperature measurements using the electrodes as classic Langmuir probes by voltage sweeping or as Mirror probes [17]; in addition, the ball-pen techniques [15,18] can be exploited.…”

Section: Discussionmentioning

confidence: 99%

Design of embedded electrostatic sensors for the RFX-mod2 device

et al. 2019

View full text Add to dashboard Cite

The RFX-mod experiment is currently undergoing a challenging upgrade of the machine assembly. One of the main purposes of RFX-mod2, the upgraded device, is the achievement of better performances by decreasing the tearing modes amplitude in Reversed-Field Pinch (RFP) configuration thanks to a higher plasma-shell proximity. Moreover, most of the innovations characterizing the device and its diagnostics are conceived with the aim of operating as both RFP and tokamak. These different configurations are taken into account in the electrostatic sensors design and layout. RFX-mod2 will be equipped with poloidal and toroidal arrays of electrostatic probes, measuring plasma density and temperature, plasma potential, particle and energy fluxes and floating potential fluctuations. Two toroidal arrays of 72 probes each (one on the high field side and one on the low field side), along with four poloidal arrays of 28 elements, are foreseen. Such a large amount of sensors is due to the requirement of a better characterization of the numerous instabilities observed in the RFP plasma edge, with the possibility to study the plasma shape in different tokamak configurations (circular, single null, double null). Three different kinds of Langmuir probe configurations will be installed: single probes, 5-pin balanced triple probes and ball-pen probes. The conceptual design of the sensors takes inspiration from the model successfully installed on RFX-mod, that allows the removal of tiles in case of damage, by means of a remote handling manipulator. K: Plasma diagnostics -probes; Analysis and statistical methods 1Corresponding author.

show abstract

Section: Discussionmentioning

confidence: 99%

Design of embedded electrostatic sensors for the RFX-mod2 device

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Indeed, a combination of BPP and Langmuir probe (LP) can be used to measure T e fluctuations [20,22]. In addition, fast sweeping of a BPP was recently shown to measure T i fluctuations, down to 10 µs [23]. As this resolution already coincides with a typical blob autocorrelation time observed on COMPASS [24], it therefore enables us to study also the ion temperature characteristics in detail.…”

Section: Introductionmentioning

confidence: 92%

Statistical properties of ion and electron temperature fluctuations in the edge of the COMPASS tokamak

Cipciar

Adámek

Horáček

et al. 2022

Plasma Phys. Control. Fusion

Self Cite

View full text Add to dashboard Cite

This paper presents measurements of the plasma turbulence with an emphasis on the ion temperature fluctuations in comparison to the electron temperature and the ion saturation current fluctuations in the edge of the COMPASS tokamak. The ion temperature values are obtained by using a fast swept ball-pen probe, with temporal resolution up to 10 µs, accompanied by independent 1 µs measurements of the electron temperature and ion saturation current. The experimental results obtained for a wide range of line-averaged densities show that statistical properties of the fluctuations are in good agreement with a Beta or Gamma distribution function. In addition, the dependence of the averaged ion and electron temperatures on the line-averaged density is studied in the near and main Scrape Off Layer region.

show abstract

“…In particular, due to an extremely low (µA) current, the reversed field analyzer (RFA) cannot measure quickly enough to resolve ELMs nor turbulence. Only recently, the fast-sweeping of a ball-pen probe (BPP) demonstrated that it could measure not only slow T i profiles [3] consistent with RFA measurements, but also 100 kHz turbulence [4]. For low temporal resolution, it was shown with both RFA [5] and BPP [3] that, whilst at separatrix T i ∼ T e , in the far scrape-off layer (SOL) T i ≫ T e because ions cool down much slower than electrons do [6].…”

Section: Motivation For Fast T I Elm Estimationmentioning

confidence: 99%

ELM temperature in JET and COMPASS tokamak divertors

et al. 2023

Self Cite

View full text Add to dashboard Cite

Analysis of the divertor ELM electron temperature at a uniquely high temporal resolution (1e-5 s) was reported at the JET tokamak [C. Guillemaut et al. Nucl. Fusion 58 (2018) 066006]. By collecting divertor probe data obtained during many dozens of ELMs, the conditional-average technique (CAV) yields surprisingly low peak electron temperatures, much below the pedestal ones (a reduction by 70% up to 99%!) which we, however, question. This result was interpreted through the collisional free-streaming kinetic model of ELMs, by a transfer of most of the electron energy to ions, implying a high tungsten sputtering for unmitigated ELMs in future fusion devices like ITER. Recently, direct microsecond temperature measurements on the COMPASS tokamak, however, showed that the electron temperature peak of ELM filaments measured in the divertor is reduced by less than ⅓ with respect to the pedestal one. This was further confirmed by a dedicated 1D PIC simulation and tends to prove that the pedestal electrons can transfer only their parallel energy to ions (due to low collisionality), thus less than ⅓ as is predicted by the collision-less free-streaming model. This finding is in strong contradiction with the JET observations. We have therefore compared the CAV to the direct (microsecond) ball-pen and Langmuir probes measurements in COMPASS and found very good agreement between them. Revisiting the mentioned JET CAV analysis yields indeed that the electron temperatures are much higher than previously reported, nearly as predicted by the PIC simulation, and thus the ion energy seems not significantly increasing in the SOL.

show abstract

Ion temperature measurements in the tokamak scrape-off layer with high temporal resolution

Cited by 6 publications

References 28 publications

Design of embedded electrostatic sensors for the RFX-mod2 device

Design of embedded electrostatic sensors for the RFX-mod2 device

Statistical properties of ion and electron temperature fluctuations in the edge of the COMPASS tokamak

ELM temperature in JET and COMPASS tokamak divertors

Contact Info

Product

Resources

About