Design, Development, and Operation of Seven Channels’ 100-GHz Interferometer for Plasma Density Measurement

Atrey, P K; Pujara, Dhaval; Mukherjee, S.; Tanna, R.L.

doi:10.1109/tps.2018.2890307

Cited by 19 publications

(12 citation statements)

References 11 publications

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“…The measuring systems used in these experiments include various external magnetic sensors for current, voltage plasma position, stored energy and Mirnov oscillation measurements [21]. Microwave interferometer is used for electron density measurement [22] and electron temperature is deduced from the Soft X-ray emission measurement using foil-ratio technique [24]. PMT-filter based spectroscopic systems and visible spectrometers are used for Hα and low Z impurity emission monitoring as well as plasma column boundary position measurements [10,23].…”

Section: Aditya-u Operations and Experimental Progressmentioning

confidence: 99%

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: Aditya-u Operations and Experimental Progressmentioning

confidence: 99%

Overview of recent experimental results from the ADITYA-U tokamak

Tanna¹,

Macwan²,

Ghosh³

et al. 2022

Nucl. Fusion

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“…The rotation measurements are carried out in discharges in the toroidal belt-limiter configuration, and the plasma and machine parameters of the discharges analyzed are as follows: current Ip = ~100 kA and plasma duration of ~250-300 ms with line-averaged electron density ne = 1-6 × 10 19 m 3 and central electron temperature T e in the range of 500 eV-1 keV. The central line-integrated electron density has been measured using a microwave interferometer diagnostic [28], whereas the central electron temperature has been measured using soft x-ray diagnostics.…”

Section: Experimental Set-upmentioning

confidence: 99%

Observations of toroidal plasma rotation reversal in the Aditya-U tokamak

et al. 2019

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An impurity ion toroidal rotation profile has been observed in the ohmic discharges of the Aditya-U tokamak from the Doppler-shifted passive charge exchange line emission of C 5+ at 529 nm. The line has been monitored using a space-resolved visible spectroscopy diagnostic consisting of a 1 m multi-track spectrometer coupled with a charge coupled device (CCD) detector. In typical discharges with central chord-averaged electron density ≲2.5 × 10 19 m −3 , the maximum toroidal rotation velocity at the plasma core is found to be −20 km s −1 in the counter-current direction. Reversal of plasma toroidal rotation is observed for high electron density discharges with a central chord-averaged density of ~5 × 10 19 m −3 . During the rotation reversal, the direction of toroidal rotation changes to the co-current direction in the core. Interestingly, in the discharges with a central chord-averaged electron density of ≲2.5 × 10 19 m −3 , where neon gas is injected at the plasma current flat-top, the toroidal rotation reversal has been observed after the gas puff.

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“…During the present experiments, the central chord-averaged density has been measured using a 100 GHz heterodyne microwave interferometer 36 . For measuring the radial electron density profile, a four-channel homodyne microwave interferometer system, having the viewing chords passing through 0, 7, 14 and 21 cm of plasma minor radius with a temporal resolution of ∼10 μs has been used 37 . An Abel-like matrix inversion technique is used to get the radial profile of electron density from the chord averaged measurement 38 .…”

Section: Methodsmentioning

confidence: 99%

Role of pinch in Argon impurity transport in Ohmic discharges of Aditya-U Tokamak

Shah,

Ghosh,

Patel

et al. 2023

Preprint

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We present experimental results of the trace argon impurity puffing in the Ohmic plasmas of Aditya-U tokamak performed to study the argon transport behaviour. Argon line emissions in visible and Vacuum Ultra Violet (VUV) spectral ranges arising from the plasma edge and core respectively are measured simultaneously. During the experiments, space resolved brightness profile of Ar1+ line emissions at 472.68 nm (3p44s 2P1.5 - 3p44p 2D1.5), 473.59 nm (3p44s 4P2.5 - 3p44p 4P1.5), 476.48 nm (3p44s 2P0.5 - 3p44p 2P1.5), 480.60 nm (3p44s 4P2.5 - 3p44p 4P2.5) are recorded using a high resolution visible spectrometer. Also, a VUV spectrometer has been used to simultaneously observe Ar13+ line emission at 18.79 nm (2s22p 2P1.5 - 2s2p2 2P1.5) and Ar14+ line emission at 22.11 nm (2s2 1S0 - 2s2p 1P1). The diffusivity and convective velocity of Ar are obtained by comparing the measured radial emissivity profile of Ar1+ emission and the line intensity ratio of Ar13+ and Ar14+ ions, with those simulated using the impurity transport code, STRAHL. Argon diffusivities ~ 12 m2/s and ~ 0.3 m2/s have been observed in the edge (ρ > 0.85) and core region of the Aditya-U, respectively. The diffusivity values both in the edge and core region are found to be higher than the neo-classical values suggesting that the argon impurity transport is mainly anomalous in the Aditya-U tokamak. Also, an inward pinch of ~ 10 m/s mainly driven by Ware pinch is required to match the measured and simulated data. The measured peaked profile of Ar density suggests impurity accumulation in these discharges.

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Design, Development, and Operation of Seven Channels’ 100-GHz Interferometer for Plasma Density Measurement

Cited by 19 publications

References 11 publications

Overview of recent experimental results from the ADITYA-U tokamak

Overview of recent experimental results from the ADITYA-U tokamak

Observations of toroidal plasma rotation reversal in the Aditya-U tokamak

Role of pinch in Argon impurity transport in Ohmic discharges of Aditya-U Tokamak

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