### Abstract

The impact of resonant magnetic perturbations (RMPs) on the power required to access H-mode is examined experimentally on MAST. Applying RMP in *n* = 2, 3, 4 and 6 configurations delays the L-H transition at low applied fields and prevents the transition at high fields. The experiment was primarily performed at RMP fields sufficient to cause moderate increases in ELM frequency, f_{mitigated}/ f_{natural} ∼ 3. To obtain H-mode with RMPs at this field, an increase of injected beam power is required of at least 50% for *n* = 3 and *n* = 4 RMP and 100% for *n* = 6 RMP. In terms of power threshold, this corresponds to increases of at least 20% for *n* = 3 and *n* = 4 RMPs and 60% for *n* = 6 RMPs. This 'RMP affected' power threshold is found to increase with RMP magnitude above a certain minimum perturbed field, below which there is no impact on the power threshold. Extrapolations from these results indicate large increases in the L-H power threshold may be required for discharges requiring large mitigated ELM frequency.

Language | English |
---|---|

Article number | 075013 |

Journal | Plasma Physics and Controlled Fusion |

Volume | 57 |

Issue number | 7 |

DOIs | |

Publication status | Published - 18 Jun 2015 |

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### Keywords

- ELM frequency
- L-H power threshold
- L-H threshold
- mitigated ELM frequency
- resonant magentic perturbations
- RMP

### Cite this

*Plasma Physics and Controlled Fusion*,

*57*(7), [075013]. https://doi.org/10.1088/0741-3335/57/7/075013

}

*Plasma Physics and Controlled Fusion*, vol. 57, no. 7, 075013. https://doi.org/10.1088/0741-3335/57/7/075013

**Impact of resonant magnetic perturbations on the L-H transition on MAST.** / Scannell, R; Kirk, A; Carr, M; Hawke, J; Henderson, S S; O'Gorman, T; Patel, A; Shaw, A.; Thornton, A.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Impact of resonant magnetic perturbations on the L-H transition on MAST

AU - Scannell, R

AU - Kirk, A

AU - Carr, M

AU - Hawke, J

AU - Henderson, S S

AU - O'Gorman, T

AU - Patel, A

AU - Shaw, A.

AU - Thornton, A

PY - 2015/6/18

Y1 - 2015/6/18

N2 - The impact of resonant magnetic perturbations (RMPs) on the power required to access H-mode is examined experimentally on MAST. Applying RMP in n = 2, 3, 4 and 6 configurations delays the L-H transition at low applied fields and prevents the transition at high fields. The experiment was primarily performed at RMP fields sufficient to cause moderate increases in ELM frequency, fmitigated/ fnatural ∼ 3. To obtain H-mode with RMPs at this field, an increase of injected beam power is required of at least 50% for n = 3 and n = 4 RMP and 100% for n = 6 RMP. In terms of power threshold, this corresponds to increases of at least 20% for n = 3 and n = 4 RMPs and 60% for n = 6 RMPs. This 'RMP affected' power threshold is found to increase with RMP magnitude above a certain minimum perturbed field, below which there is no impact on the power threshold. Extrapolations from these results indicate large increases in the L-H power threshold may be required for discharges requiring large mitigated ELM frequency.

AB - The impact of resonant magnetic perturbations (RMPs) on the power required to access H-mode is examined experimentally on MAST. Applying RMP in n = 2, 3, 4 and 6 configurations delays the L-H transition at low applied fields and prevents the transition at high fields. The experiment was primarily performed at RMP fields sufficient to cause moderate increases in ELM frequency, fmitigated/ fnatural ∼ 3. To obtain H-mode with RMPs at this field, an increase of injected beam power is required of at least 50% for n = 3 and n = 4 RMP and 100% for n = 6 RMP. In terms of power threshold, this corresponds to increases of at least 20% for n = 3 and n = 4 RMPs and 60% for n = 6 RMPs. This 'RMP affected' power threshold is found to increase with RMP magnitude above a certain minimum perturbed field, below which there is no impact on the power threshold. Extrapolations from these results indicate large increases in the L-H power threshold may be required for discharges requiring large mitigated ELM frequency.

KW - ELM frequency

KW - L-H power threshold

KW - L-H threshold

KW - mitigated ELM frequency

KW - resonant magentic perturbations

KW - RMP

UR - http://www.scopus.com/inward/record.url?scp=84936750154&partnerID=8YFLogxK

UR - http://iopscience.iop.org/0741-3335/

U2 - 10.1088/0741-3335/57/7/075013

DO - 10.1088/0741-3335/57/7/075013

M3 - Article

VL - 57

JO - Plasma Physics and Controlled Fusion

T2 - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 7

M1 - 075013

ER -