3rd harmonic electron cyclotron resonant heating absorption enhancement by 2nd harmonic heating at the same frequency in a tokamak

Gnesin, Silvano; Decker, J.; Coda, S.; Goodman, T. P.; Peysson, Y.; Mazon, D.

doi:10.1088/0741-3335/54/3/035002

Cited by 10 publications

(10 citation statements)

References 21 publications

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“…An attempt to measure the effect experimentally was, however, unsuccessful as it proved impossible to disentangle from other, unrelated effects [32].…”

Section: Ecrh Physicsmentioning

confidence: 99%

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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“…An attempt to measure the effect experimentally was, however, unsuccessful as it proved impossible to disentangle from other, unrelated effects [32].…”

Section: Ecrh Physicsmentioning

confidence: 99%

Overview of recent and current research on the TCV tokamak

Coda

2013

Nucl. Fusion

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“…Being the beam duct port installed at the torus middle plane, off-axis NBI is obtained on TCV by vertically shifting the plasma magnetic axis (z), values up to |z|=13cm have been explored. In this work, fully non-inductive operation is achieved with additional 3.2 MW of ECRH power [3], which is transferred to the plasma through both X2 (P=2.3 MW) and X3 (P=0.9 MW) waves. It is worth noticing that X3 waves do not provide any net current drive on TCV, being their wave vector aiming at the plasma core perpendicularly to the magnetic field to maximize the power absorption.…”

Section: Introductionmentioning

confidence: 99%

Extension of the operating space of high-b _N fully non-inductive scenarios on TCV using neutral beam injection

et al. 2019

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The fully non-inductive sustainment of high normalized beta plasmas (betaN) is a crucial challenge for the steadystate operation of a tokamak reactor. In order to assess the difficulties found on such scenarios, steady-state regimes have been explored at the Tokamak à Configuration Variable (TCV) using the newly available 1MW Neutral Beam Injection (NBI) system. The operating space is extended towards plasmas that are closer to those expected in JT-60SA and ITER, i.e. with significant NBI and Electron Cyclotron Resonance Heating and Current Drive (ECRH/CD), bootstrap current and Fast Ion (FI) fraction. BetaN values up to 1.4 and 1.7 are obtained in lower single null L-mode (H 98 (y,2)~0.8) and H-mode (H 98 (y,2)~1) plasmas, respectively, at zero time averaged loop voltage and q 95~6 . Fully non-inductive operation is not achieved with NBI alone, whose injection can even increase the loop voltage in presence of EC waves. A strong contribution to the total plasma pressure of bulk and FIs from NBI is experimentally evidenced and confirmed by interpretative ASTRA and NUBEAM modelling, which further predicts that FI charge-exchange reactions are the main loss channel for NBH/CD efficiency. Internal transport barriers, which are expected to maximize the bootstrap current fraction, are not formed in either the electron or the ion channel in the plasmas explored to date, despite a significant increase in the toroidal rotation and FIs fraction with NBI, which are known to reduce turbulence. First results on scenario development of high-betaN fully noninductive H-mode plasmas are also presented.

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“…Electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) launcher system has installed on the KSTAR tokamak. An ECH/ECCD system is required for localized plasma heating, plasma startup for large superconducting tokamak device, preionization for low voltage startup, non-inductive current drive, and discharge cleaning of a vacuum vessel [1][2][3]. Recently, ECH/ECCD system is used in MHD instability modes control such as suppression of neoclassical tearing mode (NTM), control of sawtooth and internal transport barriers for high-performance and stability of the plasma [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Design of a steerable launcher for the ECH system on KSTAR

et al. 2017

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Abstract. 105/140Ghz dual frequency gyrotron is used in KSTAR tokamak for an electron cyclotron resonance heating (ECRH). The ECH launcher consists of a fixed mirror, a steering mirror, cooling systems and some mechanical component for a steering mirror. We have designed the fixed ellipsoidal focusing mirror for an efficient heating and localized control. The beam radius using the existing ECH launcher system is about 45 mm at the resonance layer. On the other hand, the modified launcher mirror reduces the beam size at the resonance layer for incident RF beam to 38 mm. The design results showed good agreement compared with the computation and simulation results. Since the distance between the corrugated waveguide and the fixed focusing mirror is fixed, it is difficult to more reduce the beam size. However, reduced beam size is small enough to localize MHD control and heating.

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3rd harmonic electron cyclotron resonant heating absorption enhancement by 2nd harmonic heating at the same frequency in a tokamak

Cited by 10 publications

References 21 publications

Overview of recent and current research on the TCV tokamak

Overview of recent and current research on the TCV tokamak

Extension of the operating space of high-b _N fully non-inductive scenarios on TCV using neutral beam injection

Design of a steerable launcher for the ECH system on KSTAR

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3rd harmonic electron cyclotron resonant heating absorption enhancement by 2nd harmonic heating at the same frequency in a tokamak

Cited by 10 publications

References 21 publications

Overview of recent and current research on the TCV tokamak

Overview of recent and current research on the TCV tokamak

Extension of the operating space of high-b N fully non-inductive scenarios on TCV using neutral beam injection

Design of a steerable launcher for the ECH system on KSTAR

Contact Info

Product

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Extension of the operating space of high-b _N fully non-inductive scenarios on TCV using neutral beam injection