A set-up for a biased electrode experiment in ADITYA Tokamak

Dhyani, Pravesh; Ghosh, Joydeep; Sathyanarayana, K.; Praveenlal, V E; Gautam, Pramila; Shah, Minsha; Tanna, R.L.; Kumar, Pintu; Chavda, Chhaya; Patel, N C; Panchal, V. K.; Gupta, C.N.; Jadeja, K. A.; Bhatt, S. B.; Kumar, Sunil; Raju, D.; Atrey, P.K.; Joisa, S.; Chattopadhyay, P. K.; Saxena, Y. C.

doi:10.1088/0957-0233/25/10/105903

Cited by 7 publications

(7 citation statements)

References 27 publications

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Section: Experimental Set-upmentioning

confidence: 99%

“…As plasma rotation shear is known to stabilize MHD modes [26,27], when the rotation shear becomes equal to magnetic shear in our experiments at a particular bias voltage ( 180 V), the tearing modes generated due to gas puff are stabilized and the disruptions caused by these modes are avoided. A detailed description of disruption avoidance can be found in [22,23].…”

Section: Disruption Avoidancementioning

confidence: 99%

“…Typical plasma parameters for the discharges presented in this article are B φ ∼ 0.75 − 0.84 T, plasma current ∼70-80 kA, discharge duration ∼80-100 ms, chord averaged central electron density n e ∼ (1 − 2) × 10 19 m −3 , central electron temperature T e ∼ 300 − 450 eV, and edge safety factor q ∼ 3 − 4.For the disruption avoidance experiments using the biased electrode technique[22], a movable cylindrical molybdenum electrode of 0.5 cm diameter and 2.0 cm exposed length is placed 3.0 cm inside the LCFS (r elec = 22.0 cm) from the top port of the machine. The electrode is powered by a capacitor-bank based pulsed power supply (PPS) using a semiconductor controlled rectifier (SCR) as a switch with forced commutation[23]. For controlling the disruptions by ICR technique, an ICR pulse of ∼50-70 kW is launched through a fast wave poloidal type antenna with a Faraday shield placed outside the LCFS.…”

mentioning

confidence: 99%

“…For controlling the disruptions by ICR technique, an ICR pulse of ∼50-70 kW is launched through a fast wave poloidal type antenna with a Faraday shield placed outside the LCFS. For real time control, a special comparator trigger circuit[23] based on MHD signals and H α emissions as precursors is used to trigger the electrode biasing and ICR pulses during disruptions.The RE mitigation experiment in ADITYA is performed by applying a LVF at one toroidal location using two Helmholtz like coils placed at the top and the bottom of the machine. The coils are connected in series to produce LVF perturbation in the direction opposite to the actual equilibrium field and are powered by a capacitor bank power supply.…”

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confidence: 99%

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Novel approaches for mitigating runaway electrons and plasma disruptions in ADITYA tokamak

Tanna¹,

Ghosh²,

Chattopadhyay³

et al. 2015

Nucl. Fusion

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This paper summarizes the results of recent dedicated experiments on disruption control and runaway mitigation carried out in ADITYA, which are of the utmost importance for the successful operation of large size tokamaks, such as ITER. It is quite a well-known fact that disruptions in tokamaks must be avoided. Disruptions, induced by hydrogen gas puffing, are successfully avoided by two innovative techniques in ADITYA using a bias electrode placed inside the last closed flux surface and applying an ion cyclotron resonance pulse with a power of ∼50 to 70 kW. These experiments led to better understanding of the disruption avoidance mechanisms and also can be thought of as one of the options for disruption avoidance in ITER. In both cases, the physical mechanism seems to be the control of magnetohydrodynamic modes due to increased poloidal rotation of edge plasma generated by induced radial electric fields. Real time avoidance of disruption with identifying proper precursors in both the mechanisms is successfully attempted. Further, analysing thoroughly the huge database of different types of spontaneous and deliberately-triggered disruptions from ADITYA, a significant contribution has been made to the international disruption database (ITPA). Furthermore, the mitigation of the runaway electron generated mainly during disruptions remains a challenging topic in present tokamak research as these high-energy electrons can cause severe damage to in-vessel components and the vacuum vessel. A simple technique has been implemented in ADITYA to mitigate the runaway electrons before they can gain high energies using a localized vertical magnetic field perturbation applied at one toroidal location to extract runaway electrons.

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Section: Experimental Set-upmentioning

confidence: 99%

Section: Disruption Avoidancementioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Novel approaches for mitigating runaway electrons and plasma disruptions in ADITYA tokamak

Tanna¹,

Ghosh²,

Chattopadhyay³

et al. 2015

Nucl. Fusion

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“…A special comparator trigger circuit [4] which detects the MHD signals and H␣ emissions as precursors to trigger the electrode biasing and ICR pulses to control/avoid disruptions respectively. A low cost microcontroller based circuit is designed and developed in-house and used in the real time disruption and runaway mitigation/control experiments in ADITYA tokamak.…”

Section: Introductionmentioning

confidence: 99%

Multi-channel control circuit for real-time control of events in Aditya tokamak

Edappala

Shah

Rajpal

et al. 2016

Fusion Engineering and Design

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Disruption mitigation using ion cyclotron wave in ADITYA tokamak

et al. 2021

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Controlling and mitigating plasma disruptions are a matter of serious concern for tokamak operation since they can cause serious damage to the machine. Dedicated experiments on disruption mitigation have been carried out in ADITYA (R = 75 cm, a = 25 cm), an Ohmically heated circular limiter tokamak. A rapid growth of magneto hydrodynamic (MHD) modes is found to be the major cause of disruptions in ADITYA tokamak. Stimulated disruptions induced by hydrogen gas puffing are successfully mitigated through stabilization of these MHD modes by applying a biased-electrode placed inside the last-closed flux surface prior to the gas injection. However, as biased electrodes cannot be placed inside the plasma in bigger tokamaks, the application of ion-cyclotron waves (ICWs) prior to disruption has been successfully attempted to mitigate disruptions through stabilization of MHD modes in ADITYA tokamak. The amplitude of MHD modes (m/n = 3/1, 2/1) is significantly reduced upon the application of ICW prior to disruption, and the stimulated disruptions are successfully mitigated by preventing the growth and overlapping of these MHD modes. These experimental results demonstrate that MHD driven disruptions may be mitigated due to stabilization of m = 2 modes by ponderomotive force of the IC waves.

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A set-up for a biased electrode experiment in ADITYA Tokamak

Cited by 7 publications

References 27 publications

Novel approaches for mitigating runaway electrons and plasma disruptions in ADITYA tokamak

Novel approaches for mitigating runaway electrons and plasma disruptions in ADITYA tokamak

Multi-channel control circuit for real-time control of events in Aditya tokamak

Disruption mitigation using ion cyclotron wave in ADITYA tokamak

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