Investigation of Recycling and Impurities Influxes in ADITYA-U Tokamak Plasmas

Yadava, Nandini; Chowdhuri, M. B.; Ghosh, Joydeep; Manchanda, R.; Macwan, Tanmay; Ramaiya, N.; Pandya, Ankur; K, Sripathi Punchithaya; ISMAYIL, -; Jadeja, K. A.; Nagora, Umesh; Pathak, S.K.; Shah, Minsha; Gautam, Pramila; Kumar, Rohit; Aich, Suman; Patel, Kaushal; Tanna, R.L.; Team, Aditya-U

doi:10.1585/pfr.16.2402055

Cited by 4 publications

(6 citation statements)

References 23 publications

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“…The results clearly indicate that the influxes of hydrogen and O 1+ are higher from limiter compared to influxes from the wall, while the influxes of C 2+ from limiter and wall are nearly the same. The limiter is a big source of oxygen impurities and hydrogen neutrals [53]. The integrated influxes of hydrogen and oxygen from wall are almost comparable to that of limiter indicating the important role played by wall in affecting the particle and impurity control in the plasma.…”

Section: Investigation Of Recycling and Impurities Influxes Inmentioning

confidence: 93%

“…This gives value of the absorption coefficient ∼0.25 cm −1 . From the formula of absorption coefficient [60] lithium density is calculated to be ∼2 × 10 16 cm −3 by considering lithium temperature of ∼0.025 eV, which is room temperature.…”

Section: Investigation Of Self-absorbed Lithium Spectral Line Emis-mentioning

confidence: 99%

“…Summary of measured influxes and integrated influxes from different LoS Reprinted from[53], with permission from JSPF.…”

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confidence: 99%

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Physics studies of ADITYA & ADITYA-U tokamak plasmas using spectroscopic diagnostics

et al. 2022

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Several spectroscopic diagnostics encompassing the spectral emission range from the x-ray to near infrared (NIR) have been developed, installed and operated for diagnosing and physics studies in the ADITYA and ADITYA-U tokamaks. The recycling and impurity influxes and plasma Z eff after lithium (Li) coating have been studied using a PMT (photomultiplier tube)-filter based system by capturing H α , O1+, C2+, and visible continuum emissions. Significant reduction in the Z eff values has been observed in the discharge with the Li coated walls. The measured radial profile of H α emission using a filter-PMT array, has been modelled using a neutral transport code. The results show substantial contributions from the molecular hydrogen and molecular hydrogen ion dissociation (∼56%) and charge-exchange (∼30%) processes in the measured H α emission. Furthermore, a high-resolution, 1 m spectrometer with charge coupled device detector capable of multi-track measurements, has been used to study impurity transport, neutral and ion temperature and intrinsic plasma rotation. By modelling the measured radial profile of O4+ spectral line emission using an impurity transport code, substantial contribution of edge fluctuations on the oxygen transport has been observed. The toroidal ( u T max ∼ 20 km s−1 in core) and poloidal ( u θ max ∼ 4.5 km s−1 at edge) rotation velocities are measured using C5+ (529 nm) and C2+ (464.7 nm) passive line emissions respectively. The measurement of radial profile of toroidal plasma rotation revealed a reversal of rotation direction depending on the electron density content of the ADITYA-U plasmas. The neutral temperature measurements showed a poloidal asymmetry indicating a presence of asymmetrical source of neutral heating. Moreover, the modelling of measured Fe14+ and Fe15+ vacuum ultraviolet spectral lines has revealed the neo-classical nature of iron transport in ADITYA core. Fast visible camera images captured the formation of filament structures triggered by interchange instabilities during plasma disruptions.

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Section: Investigation Of Recycling and Impurities Influxes Inmentioning

confidence: 93%

Section: Investigation Of Self-absorbed Lithium Spectral Line Emis-mentioning

confidence: 99%

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Physics studies of ADITYA & ADITYA-U tokamak plasmas using spectroscopic diagnostics

et al. 2022

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“…From a quantitative analysis using the radiation transport modelling, the absorption coefficient, opacity, and density of lithium are obtained and radiative loss is estimated. Approximately, 60% of input power seems to be radiated away due to particle injection, and the plasma is disrupted due to the radiative cooling [31].…”

Section: Microparticle Injection Experiments In Aditya-umentioning

confidence: 99%

Micro-particle injection experiments in ADITYA-U tokamak using an inductively driven pellet injector

Pahari,

P.P.,

Savita

et al. 2024

Nucl. Fusion

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A first-of-its-kind, Inductively driven micro-Particle (Pellet) accelerator and Injector (IPI) have been developed and operated successfully in ADITYA-U circular plasma operations, which may ably address the critical need for a suitable disruption control mechanism in ITER and future tokamak. The device combines the principles of electromagnetic induction, pulse power technology, impact, and fracture dynamics. It is designed to operate in a variety of environments, including atmospheric pressure and ultra-high vacuum. It can also accommodate a wide range of pellet quantities, sizes, and materials and can adjust the pellets' velocities over a coarse and fine range. The device has a modular design such that the maximum velocity can be increased by increasing the number of modules. A cluster of Lithium Titanate/Carbonate (Li2TiO3/Li2CO3) impurity particles with variable particle sizes, weighing ~ 50 – 200 mg are injected with velocities of the order of ~ 200 m/s during the current plateau in ADITYA-U tokamak. This leads to a complete collapse of the plasma current within ~ 5 – 6 ms of triggering the injector. The current quench time is dependent on the amount of impurity injected as well as the compound, with Li2TiO3 injection causing a faster current quench than Li2CO3 injection, as more power is radiated in the case of Li2TiO3. The increase in radiation due to the macro-particle injection starts in the plasma core, while the Soft X-ray emission indicates that the entire plasma core collapses at once.

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“…The Li-I spectral line intensity at 670.8 nm and H-α spectral line intensity at 656.8 nm are simultaneously recoded during plasma wall interaction in all plasma discharges with Li-coated PFCs and vessel wall. Li and H emissions are measured with filter + PMT based system and the light is collected through a radial port [25]. The filter + PMT system is calibrated for absolute intensity measurements.…”

Section: Relation Of Lithium-hydrogen During Plasma Wall Interaction ...mentioning

confidence: 99%

Lithium wall conditioning techniques in ADITYA-U tokamak for impurity and fuel control

et al. 2021

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In fusion devices, various techniques are employed for coating the plasma facing components (PFCs) including the vessel wall with low-Z material like lithium, boron, and silicon in order to enhance the plasma parameters and control. In ADITYA-Upgrade tokamak, different techniques of lithium wall conditioning are developed and implemented to obtain uniform and sustainable coating of Li on PFCs and the vessel wall. In this paper, two techniques used to generate Li from the source are reported. In one of the technique, a heated (fixed temperature of ∼120 °C) Li-rod is placed inside the hydrogen glow discharge cleaning (H-GDC) plasma and the sputtered Li by hydrogen (H) ions and atoms coats the wall and periphery. In the second technique, the Li is vapourized using a high-temperature Li-evaporator and released into the H-GDC plasma for uniform coating of Li on the PFCs and vessel. Significantly enhanced plasma parameters are obtained after Li coating by both techniques, with the evaporated Li performed better than the Li rod case. With the Li coating obtained with evaporated Li at 600 °C (550 mg Li) with H-GDC, the Li wall conditioning has been observed to be sustaining for in a larger number of plasma discharges in comparison to non-H-GDC assisted Li deposition. As the melting temperature of lithium hydride (LiH) is much higher (688.7 °C) than that of lithium (180.5 °C), this enhance the longer Li-coating lifetime relatively due to the formation of Li–H molecules on the vessel wall and PFCs. In ADITYA-U the carbon impurity and hydrogen recycling, due to relatively high surface area of graphite PFCs as well as their proximity to the plasma, limits the plasma performance and effective controls. Hence, H-GDC, H-GDC with Li-rod sputtering or Li evaporation, helium-GDC, argon–hydrogen mixtures-GDC in particular sequence are carried out to obtain better plasma discharges. The Li coating techniques and their effect on tokamak plasma discharges of ADITYA-U are discussed in this paper.

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Investigation of Recycling and Impurities Influxes in ADITYA-U Tokamak Plasmas

Cited by 4 publications

References 23 publications

Physics studies of ADITYA & ADITYA-U tokamak plasmas using spectroscopic diagnostics

Physics studies of ADITYA & ADITYA-U tokamak plasmas using spectroscopic diagnostics

Micro-particle injection experiments in ADITYA-U tokamak using an inductively driven pellet injector

Lithium wall conditioning techniques in ADITYA-U tokamak for impurity and fuel control

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