Observation of enhanced ion particle transport in mixed H/D isotope plasmas on JET

JET Contributors

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)

Abstract

Particle transport in tokamak plasmas has been intensively studied in the past, particularly in relation to density peaking and the presence of anomalous inward particle convection in L- and H-modes. While in the L-mode case the presence of the anomalous inward pinch has previously been unambiguously demonstrated, particle transport in the H-mode was unclear. The main difficulty of such studies is that particle diffusion and convection could not be measured independently in steady-state conditions in the presence of a core particle flux. Therefore, it is usually not possible to separate the transport effect(inward convection), from the source effect (slow diffusion of particles introduced to the plasma core by neutral beam injection heating). In this work we describe experiments done on JET with mixtures of two hydrogenic isotopes: H and D. It is demonstrated that in the case of several ion species, convection and diffusion can be separated in a steady plasma without implementation of perturbative techniques such as gas puff modulation. Previous H-mode density peaking studies suggested that for this relatively high electron collisionality plasma scenario, the observed density gradient is mostly driven by particle source and low particle diffusivity D < 0.5 ∗ χ eff. Transport coefficients derived from observation of the isotope profiles in the new experiments far exceed that value - ion particle diffusion is found to be as high as D 2 ∗ χ eff, combined with a strong inward convection. Apparent disagreement with previous findings was explained by significantly faster transport of ion components with respect to the electrons, which could not be observed in a single main ion species plasma. This conclusion is confirmed by quasilinear gyrokinetic simulations.

Original languageEnglish
Article number076022
JournalNuclear Fusion
Volume58
Issue number7
DOIs
Publication statusPublished - 4 Jun 2018
MoE publication typeNot Eligible

Fingerprint

isotopes
convection
particle diffusion
ions
beam injection
neutral beams
electron plasma
flux (rate)
diffusivity
transport properties
modulation
gradients
heating
profiles
gases
electrons
simulation

Keywords

  • particle transport
  • Plasma
  • tokamak

Cite this

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title = "Observation of enhanced ion particle transport in mixed H/D isotope plasmas on JET",
abstract = "Particle transport in tokamak plasmas has been intensively studied in the past, particularly in relation to density peaking and the presence of anomalous inward particle convection in L- and H-modes. While in the L-mode case the presence of the anomalous inward pinch has previously been unambiguously demonstrated, particle transport in the H-mode was unclear. The main difficulty of such studies is that particle diffusion and convection could not be measured independently in steady-state conditions in the presence of a core particle flux. Therefore, it is usually not possible to separate the transport effect(inward convection), from the source effect (slow diffusion of particles introduced to the plasma core by neutral beam injection heating). In this work we describe experiments done on JET with mixtures of two hydrogenic isotopes: H and D. It is demonstrated that in the case of several ion species, convection and diffusion can be separated in a steady plasma without implementation of perturbative techniques such as gas puff modulation. Previous H-mode density peaking studies suggested that for this relatively high electron collisionality plasma scenario, the observed density gradient is mostly driven by particle source and low particle diffusivity D < 0.5 ∗ χ eff. Transport coefficients derived from observation of the isotope profiles in the new experiments far exceed that value - ion particle diffusion is found to be as high as D 2 ∗ χ eff, combined with a strong inward convection. Apparent disagreement with previous findings was explained by significantly faster transport of ion components with respect to the electrons, which could not be observed in a single main ion species plasma. This conclusion is confirmed by quasilinear gyrokinetic simulations.",
keywords = "particle transport, Plasma, tokamak",
author = "M. Maslov and King, {D. B.} and E. Viezzer and Keeling, {D. L.} and C. Giroud and Tuomas Tala and Antti Salmi and M. Marin and J. Citrin and C. Bourdelle and Solano, {E. R.} and {JET Contributors}",
year = "2018",
month = "6",
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doi = "10.1088/1741-4326/aac342",
language = "English",
volume = "58",
journal = "Nuclear Fusion",
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Observation of enhanced ion particle transport in mixed H/D isotope plasmas on JET. / JET Contributors.

In: Nuclear Fusion, Vol. 58, No. 7, 076022, 04.06.2018.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Observation of enhanced ion particle transport in mixed H/D isotope plasmas on JET

AU - Maslov, M.

AU - King, D. B.

AU - Viezzer, E.

AU - Keeling, D. L.

AU - Giroud, C.

AU - Tala, Tuomas

AU - Salmi, Antti

AU - Marin, M.

AU - Citrin, J.

AU - Bourdelle, C.

AU - Solano, E. R.

AU - JET Contributors

PY - 2018/6/4

Y1 - 2018/6/4

N2 - Particle transport in tokamak plasmas has been intensively studied in the past, particularly in relation to density peaking and the presence of anomalous inward particle convection in L- and H-modes. While in the L-mode case the presence of the anomalous inward pinch has previously been unambiguously demonstrated, particle transport in the H-mode was unclear. The main difficulty of such studies is that particle diffusion and convection could not be measured independently in steady-state conditions in the presence of a core particle flux. Therefore, it is usually not possible to separate the transport effect(inward convection), from the source effect (slow diffusion of particles introduced to the plasma core by neutral beam injection heating). In this work we describe experiments done on JET with mixtures of two hydrogenic isotopes: H and D. It is demonstrated that in the case of several ion species, convection and diffusion can be separated in a steady plasma without implementation of perturbative techniques such as gas puff modulation. Previous H-mode density peaking studies suggested that for this relatively high electron collisionality plasma scenario, the observed density gradient is mostly driven by particle source and low particle diffusivity D < 0.5 ∗ χ eff. Transport coefficients derived from observation of the isotope profiles in the new experiments far exceed that value - ion particle diffusion is found to be as high as D 2 ∗ χ eff, combined with a strong inward convection. Apparent disagreement with previous findings was explained by significantly faster transport of ion components with respect to the electrons, which could not be observed in a single main ion species plasma. This conclusion is confirmed by quasilinear gyrokinetic simulations.

AB - Particle transport in tokamak plasmas has been intensively studied in the past, particularly in relation to density peaking and the presence of anomalous inward particle convection in L- and H-modes. While in the L-mode case the presence of the anomalous inward pinch has previously been unambiguously demonstrated, particle transport in the H-mode was unclear. The main difficulty of such studies is that particle diffusion and convection could not be measured independently in steady-state conditions in the presence of a core particle flux. Therefore, it is usually not possible to separate the transport effect(inward convection), from the source effect (slow diffusion of particles introduced to the plasma core by neutral beam injection heating). In this work we describe experiments done on JET with mixtures of two hydrogenic isotopes: H and D. It is demonstrated that in the case of several ion species, convection and diffusion can be separated in a steady plasma without implementation of perturbative techniques such as gas puff modulation. Previous H-mode density peaking studies suggested that for this relatively high electron collisionality plasma scenario, the observed density gradient is mostly driven by particle source and low particle diffusivity D < 0.5 ∗ χ eff. Transport coefficients derived from observation of the isotope profiles in the new experiments far exceed that value - ion particle diffusion is found to be as high as D 2 ∗ χ eff, combined with a strong inward convection. Apparent disagreement with previous findings was explained by significantly faster transport of ion components with respect to the electrons, which could not be observed in a single main ion species plasma. This conclusion is confirmed by quasilinear gyrokinetic simulations.

KW - particle transport

KW - Plasma

KW - tokamak

UR - http://www.scopus.com/inward/record.url?scp=85049826718&partnerID=8YFLogxK

U2 - 10.1088/1741-4326/aac342

DO - 10.1088/1741-4326/aac342

M3 - Article

AN - SCOPUS:85049826718

VL - 58

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 7

M1 - 076022

ER -