Effect of periodic gas-puffs on drift-tearing modes in ADITYA/ADITYA-U tokamak discharges

Raj, Harshita; Macwan, Tanmay; Singh, Kaushlender; Dolui, Suman; Ghosh, Joydeep; Bisai, N.; Jadeja, K. A.; Patel, Ketan M.; Patel, N C; Tanna, R.L.; Raju, D.; Jha, S.; Chattopadhyay, P. K.; Sen, Abhijit; Saxena, Y. C.; Pal, Rabindranath; Team, Aditya-U

doi:10.1088/1741-4326/ab6810

Cited by 11 publications

(12 citation statements)

References 46 publications

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“…This leads to a decrease (increase) in the preexisting rotation frequency of the DTMs. Further, gas puffing during the bias voltage pulse reduces the rotation frequency, as explained by Raj et al [13]. These observations clearly indicate that the rotation of the DTMs depends on both the diamagnetic drift and the plasma rotation, and hence can be controlled by influencing either or both of these causes.…”

Section: Introductionsupporting

confidence: 60%

“…Since RE confinement is known to be sensitive to the magnetic fluctuation (MHD) [58,59], MHD activity during the application of periodic gas puff pulses has been analyzed in detail to investigate any correlation with REs. Although the gas puffs modify both MHD modes [13] and edge fluctuations [60] in ADITYA-U, it is found that the HXR amplitude exhibits no correlation with the MHD activity in these experiments (figure 21(a)) in contrast to the strong correlation observed between HXR and edge density fluctuations…”

Section: Re Confinement By Gas Puffsmentioning

confidence: 62%

“…Figure 17(a) shows the frequency-time in the magnitude of the f DTM by ∼1.5 kHz agrees well with the decrease in plasma rotation frequency in the ion-diamagnetic direction. The application of a short gas puff pulse has been observed to reduce the f DTM in the ADITYA-U tokamak [13]. The decrease or increase in the f DTM due to positive or negative bias application has been observed to be again reduced by hydrogen gas injection during the bias pulse.…”

Section: Controlling the Rotation Of Dtms Using Biased Electrode In A...mentioning

confidence: 96%

“…Furthermore, it has been shown that the rotation frequency of the DTM is a combination of diamagnetic drift and plasma rotation, and it can be controlled by separately targeting the diamagnetic drift and plasma rotation. In ADITYA-U the m/n = 2/1 drift-tearing mode (DTM) was identified, characterized and found to be rotating in the electron diamagnetic direction, and it can be modulated using periodic gas puffs [13]. The background plasma poloidal rotation in the ion diamagnetic direction is either increased or decreased by inducing an outward or inward radial electric field respectively by biasing an electrode placed in the edge region of the plasma.…”

Section: Controlling the Rotation Of Dtms Using Biased Electrode In A...mentioning

confidence: 99%

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Overview of recent experimental results from the ADITYA-U tokamak

Tanna¹,

Macwan²,

Ghosh³

et al. 2022

Nucl. Fusion

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Since the 2018 IAEA-FEC conference, in addition to expanding the parameter horizons of the ADITYA-U machine, emphasis has been given to dedicated experiments on inductively driven particle injection (IPI) for disruption studies, runaway electron (RE) dynamics and mitigation, plasma rotation reversal, radiative-improved modes using Ne and Ar injection, modulation of magneto–hydrodynamic modes, edge turbulence using periodic gas puffs and electrode biasing (E-B). Plasma parameters close to the design parameters of circular plasmas with H2 and D2 as fuel have been realized, and the shaped plasma operation has also been initiated. Consistent plasma discharges having I P ∼ 100–210 kA, t ∼ 300–400 ms, n e ∼ 3–6 × 1019 m−3, core T e ∼ 300–500 eV were achieved with a maximum B T of ∼1.5 T. The enhanced plasma parameters are the outcome of repeated cycles of baking (135 °C), followed by extensive wall conditioning, which includes pulsed glow discharge cleaning in H, He and Ar–H mixture, and lithiumization. A higher confinement time has been observed in D2 compared to H2 plasmas. Furthermore, shaped plasmas are attempted for the first time in ADITYA-U. A first of its kind inductively driven particle injection for disruption mitigation studies has been developed and operated. The injection of solid particles into the plasma core leads to a fast current quench. Two pulses of electron cyclotron resonance wave at 42 GHz are launched in a single discharge: one pulse is used for pre-ionization and the second for heating. In a novel approach, a positively biased electrode is used to confine REs after discharge termination. E-B is also used for controlling the rotation of drift-tearing modes by changing the plasma rotation. Cold pulse propagation and signatures of detachment are observed during the injection of short gas puffs. A correlation between the plasma toroidal rotation and the total radiated power has been observed with neon gas injection-induced improved confinement modes.

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Section: Introductionsupporting

confidence: 60%

Section: Re Confinement By Gas Puffsmentioning

confidence: 62%

Section: Controlling the Rotation Of Dtms Using Biased Electrode In A...mentioning

confidence: 96%

Section: Controlling the Rotation Of Dtms Using Biased Electrode In A...mentioning

confidence: 99%

See 2 more Smart Citations

Overview of recent experimental results from the ADITYA-U tokamak

Tanna¹,

Macwan²,

Ghosh³

et al. 2022

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

show abstract

“…Therefore, to control this transport and to improve the confinement time we need to control the interchange instability. For this purpose, various approaches have been taken in the past, such as use of gas puffs [6,7], and biasing the plasma with the help of electrodes in the tokamak boundary region. The tokamak boundary region consists of edge and scrape-off layer (SOL) regions.…”

Section: Introductionmentioning

confidence: 99%

Edge biasing and its impact on the edge and SOL turbulence

Shankar¹,

Bisai²,

Raj³

et al. 2022

Nucl. Fusion

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A theoretical study is made of the effect of edge biasing on the dynamics of the interchange turbulence in the edge and scrape-off layer (SOL) regions. A linear analysis of a set of model fluid equations shows that biasing stabilizes the small ky modes. The model equations are next solved numerically, using the BOUT++ framework, to explore the nonlinear dynamics in the presence of positive or negative bias and compared to results in the absence of bias. Positive biasing is found to lead to a larger increment in plasma density and temperature as compared to negative biasing. It is further observed that cross-correlation between density and poloidal electric field at different radial positions decreases for positive biasing and in the case of negative biasing it is almost similar to that of no biasing. Plasma density and poloidal electric field fluctuations have been investigated which show that the density fluctuations increase (decrease) for positive (negative) biasing but the radially outward flux for these biasing cases always decreases mainly due to the decrease of cross-correlation between density and poloidal electric field fluctuations.

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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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Effect of periodic gas-puffs on drift-tearing modes in ADITYA/ADITYA-U tokamak discharges

Cited by 11 publications

References 46 publications

Overview of recent experimental results from the ADITYA-U tokamak

Overview of recent experimental results from the ADITYA-U tokamak

Edge biasing and its impact on the edge and SOL turbulence

Disruption mitigation using ion cyclotron wave in ADITYA tokamak

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