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Development of a thin-target hard X-ray bremsstrahlung detection system to study confined runaway electrons in Aditya-U Tokamak
Authors:
Suman Dolui,
Santosh Pandya,
J. Kumar,
Bharat Hegde,
Kaushlender Singh,
J. Ghosh,
Komal Yadav,
Mitul Abhangi,
Shishir Purohit,
Minsha Shah,
Laxmikanta Pradhan,
Harshita Raj,
R. L. Tanna,
Ashok K. Kumawat,
Injamul Hoque,
Soumitra Banerjee,
Ruchi Varshney,
S. Aich,
Rohit Kumar,
K. A. Jadeja,
K. M. Patel,
M. K. Gupta,
P. K. Chattopadhyay,
A. Sen,
Y. C. Saxena
, et al. (1 additional authors not shown)
Abstract:
A specially shielded CdTe detector based hard X-ray (HXR) monitoring system equipped with a lead collimator has been developed and installed on the Aditya-U tokamak to investigate the dynamics of fast electrons (~20-200 keV) generated during sawtooth activity. The pre-existing HXR monitor in Aditya-U is exposed to the entire HXR bremsstrahlung emission from the plasma volume, peripheral limiters,…
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A specially shielded CdTe detector based hard X-ray (HXR) monitoring system equipped with a lead collimator has been developed and installed on the Aditya-U tokamak to investigate the dynamics of fast electrons (~20-200 keV) generated during sawtooth activity. The pre-existing HXR monitor in Aditya-U is exposed to the entire HXR bremsstrahlung emission from the plasma volume, peripheral limiters, and other structural components, which limits its ability to separately study the dynamics of lost and confined runaway electrons (REs). In contrast, the newly developed diagnostic has successfully measured the chord-averaged thin-target HXR bremsstrahlung emission encompassing the core plasma region, particularly within and around the sawtooth inversion radius. The measured HXR spectra are validated through forward modelling code that incorporates plasma parameters, confined RE characteristics, and the geometric configuration of the diagnostic system. The results confirm the capability of the developed HXR monitor to probe the fast-electron dynamics during internal plasma instabilities.
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Submitted 1 July, 2026;
originally announced July 2026.
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Comparison of Tomographic Reconstruction Algorithms for Infrared Imaging Video Bolometer Diagnostic in Plasma Devices
Authors:
Vinit Pandya,
Santosh P. Pandya,
Ansh Patel,
Kumudni Tahiliani,
Kumar Ajay
Abstract:
Infrared Imaging Video Bolometer (IRVB) measures total radiation power loss from plasma in 2 dimensions through a pinhole camera geometry. Where a free-standing thin metal foil act as a broad band absorber from Soft X-Rays to IR radiation. This configuration produces line-integrated signals with poloidal and toroidal coverage that must be inverted to recover the plasma radiation emissivity distrib…
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Infrared Imaging Video Bolometer (IRVB) measures total radiation power loss from plasma in 2 dimensions through a pinhole camera geometry. Where a free-standing thin metal foil act as a broad band absorber from Soft X-Rays to IR radiation. This configuration produces line-integrated signals with poloidal and toroidal coverage that must be inverted to recover the plasma radiation emissivity distribution on a poloidal cross-section. This study compares the tomographic methods implemented to IRVB brightness data reconstruction, namely Minimum Fisher Information (MFI), Phillips-Tikhonov regularization (PTR), and Maximum-Likelihood Expectation-Maximization (MLEM). The comparison assessment is organized around several aspects of bolometer measurements, namely viewing geometry configuration, non-negativity, robustness to noise, sensitivity to prior assumptions, convergence speed, and peak preservation. The present work also details the IRVB forward modelling process, construction of synthetic phantoms, and a validation of these reconstruction methods based on typical expected emissivity profiles, namely symmetric Gaussian distribution at plasma center, symmetric hollow-radiation emissivity profile, asymmetric radiation profiles across the poloidal cross-section, and divertor-side radiation emission profiles. The outcome is to emphasize the practical tradeoffs among reconstruction accuracy, numerical stability, and suitability for real-time or offline usage of these reconstruction methods, particularly for the IRVB camera viewing system.
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Submitted 17 May, 2026;
originally announced May 2026.
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A multi-purpose reciprocating probe drive system for studying the effect of gas-puffs on edge plasma dynamics in the ADITYA-U tokamak
Authors:
Kaushlender Singh,
Bharat Hegde,
Ashok K. Kumawat,
Ankit Kumar,
M. S. Khan,
Suman Dolui,
Injamul Hoque,
Tanmay Macwan,
Sharvil Patel,
Abha Kanik,
Komal Yadav,
Soumitra Banerjee,
Harshita Raj,
Devilal Kumawat,
Pramila Gautam,
Rohit Kumar,
Suman Aich,
Laxmikanta Pradhan,
Ankit Patel,
Kalpesh Galodiya,
Abhijeet Kumar,
Shwetang Pandya,
K. M. Patel,
K. A. Jadeja,
D. C. Raval
, et al. (2 additional authors not shown)
Abstract:
This article reports the development of a versatile high-speed reciprocating drive system (HRDS) with interchangeable probe heads to characterize the edge plasma region of ADITYA-U tokamak. This reciprocating probe drive system consisting of Langmuir and magnetic probe heads, is designed, fabricated, installed, and operated for studying the extent of fuel/impurity gas propagation and its influence…
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This article reports the development of a versatile high-speed reciprocating drive system (HRDS) with interchangeable probe heads to characterize the edge plasma region of ADITYA-U tokamak. This reciprocating probe drive system consisting of Langmuir and magnetic probe heads, is designed, fabricated, installed, and operated for studying the extent of fuel/impurity gas propagation and its influence on plasma dynamics in the far-edge region inside the last closed magnetic flux surface (LCFS). The HRDS is driven by a highly accurate, easy-to-control, dynamic, brushless, permanently excited synchronous servo motor operated by a PXI-commanded controller. The system is remotely operated and allows for precise control of the speed, acceleration, and distance traveled of the probe head on a shot-to-shot basis, facilitating seamless control of operations according to experimental requirements. Using this system, consisting of a linear array of Langmuir probes, measurements of plasma density, temperature, potential, and their fluctuations revealed that the fuel gas-puff impact these mean and fluctuating parameters up to three to four cm inside the LCFS. Attaching an array of magnetic probes to this system led to measurements of magnetic fluctuations inside the LCFS. The HRDS system is fully operational and serves as an important diagnostic tool for ADITYA-U tokamak.
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Submitted 8 January, 2025;
originally announced January 2025.
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MHD activity induced coherent mode excitation in the edge plasma region of ADITYA-U Tokamak
Authors:
Kaushlender Singh,
Suman Dolui,
Bharat Hegde,
Lavkesh Lachhvani,
Sharvil Patel,
Injamul Hoque,
Ashok K. Kumawat,
Ankit Kumar,
Tanmay Macwan,
Harshita Raj,
Soumitra Banerjee,
Komal Yadav,
Abha Kanik,
Pramila Gautam,
Rohit Kumar,
Suman Aich,
Laxmikanta Pradhan,
Ankit Patel,
Kalpesh Galodiya,
Daniel Raju,
S. K. Jha,
K. A. Jadeja,
K. M. Patel,
S. N. Pandya,
M. B. Chaudhary
, et al. (6 additional authors not shown)
Abstract:
In this paper, we report the excitation of coherent density and potential fluctuations induced by magnetohydrodynamic (MHD) activity in the edge plasma region of ADITYA-U Tokamak. When the amplitude of the MHD mode, mainly the m/n = 2/1, increases beyond a threshold value of 0.3-0.4 %, coherent oscillations in the density and potential fluctuations are observed having the same frequency as that of…
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In this paper, we report the excitation of coherent density and potential fluctuations induced by magnetohydrodynamic (MHD) activity in the edge plasma region of ADITYA-U Tokamak. When the amplitude of the MHD mode, mainly the m/n = 2/1, increases beyond a threshold value of 0.3-0.4 %, coherent oscillations in the density and potential fluctuations are observed having the same frequency as that of the MHD mode. The mode numbers of these MHD induced density and potential fluctuations are obtained by Langmuir probes placed at different radial, poloidal, and toroidal locations in the edge plasma region. Detailed analyses of these Langmuir probe measurements reveal that the coherent mode in edge potential fluctuation has a mode structure of m/n = 2/1 whereas the edge density fluctuation has an m/n = 1/1 structure. It is further observed that beyond the threshold, the coupled power fraction scales almost linearly with the magnitude of magnetic fluctuations. Furthermore, the rise rates of the coupled power fraction for coherent modes in density and potential fluctuations are also found to be dependent on the growth rate of magnetic fluctuations. The disparate mode structures of the excited modes in density and plasma potential fluctuations suggest that the underlying mechanism for their existence is most likely due to the excitation of the global high-frequency branch of zonal flows occurring through the coupling of even harmonics of potential to the odd harmonics of pressure due to 1/R dependence of the toroidal magnetic field.
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Submitted 23 July, 2024;
originally announced July 2024.
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Coaxial tungsten hot plate-based cathode source for Cesium plasma production confined in MPD device
Authors:
A. D. Patel,
Zubin Shaikh,
M. Sharma,
Santosh P. Pandya,
N. Ramasubramanian
Abstract:
A Multi-dipole line cusp configured Plasma Device (MPD) having six electromagnets with embedded Vacoflux-50 as a core material and a hot filament-based cathode for Argon plasma production has been characterized by changing the pole magnetic field values. For the next step ahead, a new tungsten ionizer plasma source for contact ionization cesium plasma has been designed, fabricated, and constructed…
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A Multi-dipole line cusp configured Plasma Device (MPD) having six electromagnets with embedded Vacoflux-50 as a core material and a hot filament-based cathode for Argon plasma production has been characterized by changing the pole magnetic field values. For the next step ahead, a new tungsten ionizer plasma source for contact ionization cesium plasma has been designed, fabricated, and constructed and thus plasma produced will be confined in MPD. An electron bombardment heating scheme at high voltage is adopted for heating of 6.5cm diameter tungsten plate. This article describes the detailed analysis of the design, fabrication, operation, and characterization of temperature distribution over the tungsten hot plate using the Infrared camera of the tungsten ionizer. The tungsten plate has sufficient temperature for the production of Cesium ions/plasma.
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Submitted 23 May, 2022;
originally announced May 2022.
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Simulation of runaway electron generation in fusion grade tokamak and suppression by impurity injection
Authors:
Ansh Patel,
Santosh P. Pandya
Abstract:
During disruptions in fusion-grade tokamaks like ITER, large electric fields are induced following the thermal quench (TQ) period which can generate a substantial amount of Runaway Electrons (REs) that can carry up to 10 MA current with energies as high as several tens of MeV [1-3] in current quench phase (CQ). These runaway electrons can cause significant damage to the plasma-facing-components du…
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During disruptions in fusion-grade tokamaks like ITER, large electric fields are induced following the thermal quench (TQ) period which can generate a substantial amount of Runaway Electrons (REs) that can carry up to 10 MA current with energies as high as several tens of MeV [1-3] in current quench phase (CQ). These runaway electrons can cause significant damage to the plasma-facing-components due to their localized energy deposition. To mitigate these effects, impurity injections of high-Z atoms have been proposed [1-3]. In this paper, we use a self-consistent 0D tokamak disruption model as implemented in PREDICT code [6] which has been upgraded to take into account the effect of impurity injections on RE dynamics as suggested in [4-5]. Dominant RE generation mechanisms such as the secondary avalanche mechanism as well as primary RE-generation mechanisms namely Dreicer, hot-tail, tritium decay and Compton scattering (from γ-rays emitted from activated walls) have been taken into account. In these simulations, the effect of impurities is taken into account considering collisions of REs with free and bound electrons as well as scattering from full and partially-shielded nuclear charge. These corrections were also implemented in the relativistic test particle model to simulate RE-dynamics in momentum space. We show that the presence of impurities has a non-uniform effect on the Runaway Electron Distribution function. We also show that the combined effect of pitch-angle scattering induced by the collisions with impurity ions and synchrotron emission loss results in the faster dissipation of RE-energy distribution function [7]. The variation of different RE generation mechanisms during different phases of the disruption, mainly before and after impurity injections is reported.
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Submitted 27 February, 2021;
originally announced March 2021.