Demonstration of sawtooth period locking with power modulation in TCV plasmas

Lauret, M Menno; Felici, F.; Witvoet, Gert; Goodman, T. P.; Vandersteen, Gerd; Sauter, O.; Baar, de Marco

doi:10.1088/0029-5515/52/6/062002

Cited by 34 publications

(46 citation statements)

References 13 publications

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“…d the threshold in sawtooth period for NTM destabilization in a slightly narrower period range [45], consistent with the mode. This double-backup tool set has proven robust and effectively failsafe [47,48].…”

Section: Ov/4-4supporting

confidence: 64%

Overview of recent and current research on the TCV tokamak

Coda

2013

Nucl. Fusion

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Abstract. Through a diverse research program, TCV addresses physics issues and develops tools for ITER and for the longer-term goals of nuclear fusion, relying especially on its extreme plasma shaping and ECRH launching flexibility and preparing for an ECRH and NBI power upgrade. Localized edge heating was unexpectedly found to decrease the period and relative energy loss of ELMs. Successful ELM pacing has been demonstrated by following individual ELM detection with an ECRH power cut before turning the power back up to trigger the next ELM, the duration of the cut determining the ELM frequency. Negative triangularity was also seen to reduce the ELM energy release. H-mode studies have focused on the L-H threshold dependence on the main ion species and on the divertor leg length. Both L-and H-modes have been explored in the snowflake configuration with emphasis on edge measurements, revealing that the heat flux to the strike points on the secondary separatrix increases as the X-points approach each other, well before they coalesce. In L-mode, a systematic scan of the auxiliary power deposition profile, with no effect on confinement, has ruled it out as the cause of confinement degradation. An ECRH power absorption observer based on transmitted stray radiation was validated for eventual polarization control. A new profile control methodology was introduced, relying on real-time modeling to supplement diagnostic information; the RAPTOR current transport code in particular has been employed for joint control of the internal inductance and central temperature. An internal inductance controller using the Ohmic transformer has also been demonstrated. Fundamental investigations of NTM seed island formation by sawtooth crashes and of NTM destabilization in the absence of a sawtooth trigger were carried out. Both stabilizing and destabilizing agents (ECCD on or inside the q=1 surface, respectively) were used to pace sawtooth oscillations, permitting precise control of their period. Locking of the sawtooth period to a pre-defined ECRH modulation period was also demonstrated. Sawtooth control has permitted nearly failsafe NTM prevention when combined with backup NTM stabilization by ECRH.

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Section: Ov/4-4supporting

confidence: 64%

Overview of recent and current research on the TCV tokamak

Coda

2013

Nucl. Fusion

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“…Experiments on TCV [3] show indeed convincing evidence of sawtooth locking. In these experiments, the gyrotron power was modulated with periods that were larger than the natural sawtooth period in that operating point.…”

Section: Introductionmentioning

confidence: 75%

A new mechanism for sawtooth period control

Lauret

Felici

Witvoet

et al. 2012

EPJ Web of Conferences

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“…ECRH can affect the sawtooth period by driving current near the q=1 surface, modifying the local current profile in this region [5][6][7][8][9][10][11][12]. In continuous control schemes, the ECRH power is kept constant while the ECRH deposition location is controlled in real-time to adjust the sawtooth period [8].…”

Section: Introductionmentioning

confidence: 99%

“…Alternatively the ECRH power can be modulated with a modulation period equal to the desired sawtooth period. Such control scheme is referred to in the literature as sawtooth pacing or sawtooth locking [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

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Sawtooth pacing with on-axis ICRH modulation in JET-ILW

et al. 2017

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Abstract.A novel technique for sawteeth control in tokamak plasmas using ion-cyclotron resonance heating (ICRH) has been developed in the JET-ILW tokamak [2]. Unlike previous ICRH methods, which explored the destabilization of the internal kink mode when the radiofrequency (RF) wave absorption was placed near the q=1 surface, the technique presented here consists of stabilizing the sawteeth as fast as possible by applying the ICRH power centrally and inducing a sawtooth crash by switching it off at the appropriate instant. Since it employs on-axis ICRH, this technique is aligned with other ICRH applications that require central plasma heating such as high-Z impurity control and fusion power enhancement. The validation of this method in JET-ILW L-mode discharges is presented.

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Demonstration of sawtooth period locking with power modulation in TCV plasmas

Cited by 34 publications

References 13 publications

Overview of recent and current research on the TCV tokamak

Overview of recent and current research on the TCV tokamak

A new mechanism for sawtooth period control

Sawtooth pacing with on-axis ICRH modulation in JET-ILW

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