-
Statistical validation of calorimeter inpainting with generative diffusion priors
Authors:
Himanshu Raj,
Roli Esha
Abstract:
Localized detector inefficiencies produce incomplete calorimeter data that limit the ability to perform precision measurements. We address this problem in relativistic heavy-ion collisions from a Bayesian perspective using pretrained calorimeter diffusion models as priors to reconstruct the missing signal conditioned on surrounding measurements. In this work, we conduct a systematic comparison of…
▽ More
Localized detector inefficiencies produce incomplete calorimeter data that limit the ability to perform precision measurements. We address this problem in relativistic heavy-ion collisions from a Bayesian perspective using pretrained calorimeter diffusion models as priors to reconstruct the missing signal conditioned on surrounding measurements. In this work, we conduct a systematic comparison of several diffusion-based inpainting algorithms, whose performance is evaluated using Bayesian posterior diagnostics of energy response, spatial bias, and uncertainty calibration. The reconstruction fidelity is also analyzed across collision centralities and masked region sizes. This study establishes a general validation strategy for probabilistic reconstruction of missing detector information.
△ Less
Submitted 14 August, 2026;
originally announced August 2026.
-
Production of high-quality plasma discharges via real-time control of plasma current ramp-up using neutral gas injection in Aditya-U tokamak
Authors:
Suman Dolui,
Praveenlal Edappala,
Kaushlender Singh,
J. Ghosh,
R. L. Tanna,
A. Kundu,
K. A. Jadeja,
Ankit Patel,
Rohit Kumar,
Suman Aich,
Harshita Raj,
K. M. Patel,
M. B. Chowdhuri,
P. K. Chattopadhyay,
A. Sen,
R. Pal
Abstract:
Robust control of plasma current ramp-up is an absolute necessity, as an efficient and uncontaminated plasma current ramp-up is essential for achieving prolonged, high-pressure tokamak plasma discharges. In conventional tokamaks with Ohmic breakdown, the plasma current ramp-up is achieved primarily with pre-fixed temporal profiles of the applied toroidal electric field and the equilibrium magnetic…
▽ More
Robust control of plasma current ramp-up is an absolute necessity, as an efficient and uncontaminated plasma current ramp-up is essential for achieving prolonged, high-pressure tokamak plasma discharges. In conventional tokamaks with Ohmic breakdown, the plasma current ramp-up is achieved primarily with pre-fixed temporal profiles of the applied toroidal electric field and the equilibrium magnetic field (Bv). The pre-fixed temporal profiles of these fields are often insufficient to maintain a successful plasma current ramp-up, as several unquantified dynamical variables, such as the condition of the vessel wall and plasma-facing components, influence the plasma current rise. Fuel gas injection in an appropriate quantity at a suitable time during the current ramp-up is therefore used to control the plasma current rise rate, ensuring successful plasma current start-up in Aditya-U. The gas injection time and gas quantity are controlled based on real-time measurement of plasma current rise rate using a digital signal processor (DSP) controller. This special control scheme is capable of achieving the plasma current to rise nearly at the desired rate, resulting in a successful start-up and a stable plasma discharge.
△ Less
Submitted 4 July, 2026;
originally announced July 2026.
-
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,…
▽ More
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.
△ Less
Submitted 1 July, 2026;
originally announced July 2026.
-
Effect of LH and ECR waves on plasma parameters in ADITYA Upgrade tokamak
Authors:
S. Aich,
S. Dolui,
K. Singh,
J. Ghosh,
K. A. Jadeja,
R. L. Tanna,
K. M. Patel,
K. Galodiya,
A. Patel,
L. K. Pradhan,
B. K. Shukla,
H. Mistry,
J. Patel,
H. Patel,
D. Purohit,
K. G. Parmar,
P. K. Sharma,
J. Kumar,
B. Hegde,
Abhijeet Kumar,
Vismay Raulji,
Praveenlal E. V.,
T. M. Macwan,
R. Kumar,
A. Kumar
, et al. (7 additional authors not shown)
Abstract:
The plasma discharges in ADITYA Upgrade Tokamak are produced by means of transformer action, in which Ohmically created plasma is driven by means of a secondary loop voltage. Due to reduction of plasma resistivity after a certain level of plasma temperature, Ohmic heating becomes poor and further achievement of temperature needs other heating techniques. ADITYA-U tokamak is facilitated with a 42 G…
▽ More
The plasma discharges in ADITYA Upgrade Tokamak are produced by means of transformer action, in which Ohmically created plasma is driven by means of a secondary loop voltage. Due to reduction of plasma resistivity after a certain level of plasma temperature, Ohmic heating becomes poor and further achievement of temperature needs other heating techniques. ADITYA-U tokamak is facilitated with a 42 GHz-500 kW Electron Cyclotron Resonant Heating (ECRH) system. Also, there is a Lower Hybrid Current Drive (LHCD) system installed and operated at 3.7 GHz for driving non-inductive plasma current followed by the Ohmic current drive. Though an eventual impact in the rise of plasma temperature and plasma current due to the application of ECRH and LHCD respectively are very obvious, their energy coupling with the plasma results in several interesting outcomes in a number of experimentally measured plasma parameters. The present work addresses such impactful observations that are noticed and reported for the first time in ADITYA-U Tokamak.
△ Less
Submitted 12 January, 2026;
originally announced January 2026.
-
PRISM: A MATLAB-Based Application for Structured Probe Data Management and Visualization in Tokamak Diagnostics
Authors:
Priyanka Verma,
Subhojit Bose,
Harshita Raj,
Joydeep Ghosh
Abstract:
The successful operation of tokamak experiments requires accurate documentation, tracking, and visualization of diagnostic instruments, particularly electrical probes. Traditionally, this metadata is maintained manually through handwritten logbooks or semi-digital spreadsheets, leading to inefficiencies and human errors. In response to these challenges, we present PRISM (Probe Registration and Inf…
▽ More
The successful operation of tokamak experiments requires accurate documentation, tracking, and visualization of diagnostic instruments, particularly electrical probes. Traditionally, this metadata is maintained manually through handwritten logbooks or semi-digital spreadsheets, leading to inefficiencies and human errors. In response to these challenges, we present PRISM (Probe Registration and Information System for Monitoring)-a MATLAB-based application developed using App Designer. PRISM provides a graphical user interface (GUI) that facilitates structured probe registration, metadata storage, and both 2D and 3D spatial visualization in tokamak geometries. Tested with data from the ADITYA-U tokamak, PRISM helps users enter information accurately, retrieve metadata easily, and visualize probe setups. The tool is built in a flexible way, is not limited to a specific setup, and could potentially support future developments such as digital twins and real-time control systems.
△ Less
Submitted 30 August, 2025;
originally announced September 2025.
-
Favorable modifications of Scrape-Off Layer (SOL) heat flux width through pulsed fuelling in ADITYA-U Tokamak
Authors:
SK Injamul Hoque,
Harshita Raj,
Ritu Dey,
Soumitra Banerjee,
Komal,
Kaushlender Singh,
Suman Dolui,
Ankit Kumar,
Ashok Kumawat,
Bharat Hegde,
Sharvil Patel,
Kiran Patel,
Rohit Kumar,
Suman Aich,
Pramila Gautam,
Umesh Nagora,
Asha N Adhiya,
K. A. Jadeja,
K. M. Patel,
Ankit Patel,
R. L. Tanna,
Joydeep Ghosh
Abstract:
Enhancement of the scrape-off layer (SOL) heat flux width has been observed in the ADITYA-U Tokamak following the injection of short fuel gas pulses. A notable reduction in parallel heat flux near the last closed flux surface (LCFS) is observed after each pulse. Comparative analysis indicates that pulsed fuelling is more effective in mitigating heat flux with improved core confinement than continu…
▽ More
Enhancement of the scrape-off layer (SOL) heat flux width has been observed in the ADITYA-U Tokamak following the injection of short fuel gas pulses. A notable reduction in parallel heat flux near the last closed flux surface (LCFS) is observed after each pulse. Comparative analysis indicates that pulsed fuelling is more effective in mitigating heat flux with improved core confinement than continuous gas feeding via real-time density control. Analytical and simulation works are also carried out for validation of experimental results. The analytical model shows that SOL width modification cannot be attributed solely to the decrease of temperature due to gas pulse injection; cross-field plasma diffusion also needs to increase. Simulations with the UEDGE code suggest that an increase in both the cross-field diffusion coefficient and inward pinch velocity is necessary to replicate the experimentally observed broadening of the heat flux SOL width. These findings provide insights into efficient SOL heat flux control strategies for future fusion devices.
△ Less
Submitted 1 August, 2025;
originally announced August 2025.
-
Identification and Characterization of a New Disruption Regime in ADITYA-U Tokamak
Authors:
Soumitra Banerjee,
Harshita Raj,
Sk Injamul Hoque,
Komal Yadav,
Sharvil Patel,
Ankit Kumar,
Kaushlender Singh,
Ashok Kumawat,
Bharat Hegde,
Subhojit Bose,
Priyanka Verma,
Kumudini Tahiliani,
Asha Adhiya,
Manoj Kumar,
Rohit Kumar,
Malay Bikash Chowdhuri,
Nilam Ramaiya,
Ananya Kundu,
Suman Aich,
Suman Dolui,
K. A. Jadeja,
K. M. Patel,
Ankit Patel,
Rakesh L. Tanna,
Joydeep Ghosh
Abstract:
Disruptions continue to pose a significant challenge to the stable operation and future design of tokamak reactors. A comprehensive statistical investigation carried out on the ADITYA-U tokamak has led to the observation and characterization of a novel disruption regime. In contrast to the conventional Locked Mode Disruption (LMD), the newly identified disruption exhibits a distinctive two-phase e…
▽ More
Disruptions continue to pose a significant challenge to the stable operation and future design of tokamak reactors. A comprehensive statistical investigation carried out on the ADITYA-U tokamak has led to the observation and characterization of a novel disruption regime. In contrast to the conventional Locked Mode Disruption (LMD), the newly identified disruption exhibits a distinctive two-phase evolution: an initial phase characterized by a steady rise in mode frequency with a nonlinearly saturated amplitude, followed by a sudden frequency collapse accompanied by a pronounced increase in amplitude. This behaviour signifies the onset of the precursor phase on a significantly shorter timescale. Clear empirical thresholds have been identified to distinguish this disruption type from conventional LMD events, including edge safety factor, current decay coefficient, current quench (CQ) time, and CQ rate. The newly identified disruption regime is predominantly governed by the (m/n = 2/1) drift-tearing mode (DTM), which, in contrast to typical disruptions in the ADITYA-U tokamak that involve both m/n = 2/1 and 3/1 modes, consistently manifests as the sole dominant instability. Initiated by core temperature hollowing, the growth of this mode is significantly enhanced by a synergistic interplay between a strongly localized pressure gradient and the pronounced steepening of the current density profile in the vicinity of the mode rational surface.
△ Less
Submitted 23 July, 2025;
originally announced July 2025.
-
Effect of convective transport in edge/SOL plasmas of ADITYA-U tokamak
Authors:
Ritu Dey,
Joydeep Ghosh,
Tanmay M. Macwan,
Kaushlender Singh,
M. B. Chowdhuri,
H. Raj,
R. L. Tanna,
Deepti Sharma,
T. D. Rognlien
Abstract:
The 2-D edge plasma fluid transport code, UEDGE has been used to simulate the edge region of circular limiter plasmas of ADITYA-U for modelling the measured electron density profile. The limiter geometry of ADITYA-U has been introduced in the UEDGE code, which is primarily developed and used for divertor configuration. The computational mesh defining the limiter geometry is generated by a routine…
▽ More
The 2-D edge plasma fluid transport code, UEDGE has been used to simulate the edge region of circular limiter plasmas of ADITYA-U for modelling the measured electron density profile. The limiter geometry of ADITYA-U has been introduced in the UEDGE code, which is primarily developed and used for divertor configuration. The computational mesh defining the limiter geometry is generated by a routine developed in-house, and has successfully been integrated with the UEDGE code to simulate the edge plasma parameters of ADITYA-U. The radial profiles of edge and scrape-off layer (SOL) electron density, ne and temperature are obtained from the simulations and used to model the measured ne profile using Langmuir probe array. It has been found that a convective velocity, vconv. is definitely needed in addition to the constant perpendicular diffusion coefficient, D throughout the edge and SOL regions to model the edge ne profile. The obtained vconv. is inward and radially constant with a value of 1.5 m/s and the radially constant D is ~ 0.2 m 2/s. The value of D ~ 0.2 m2/s is found to be much less than fluctuation induced diffusivities and lies in-between the neoclassical diffusivity and Bohm diffusivity estimated in the edge-SOL region of ADITYA-U tokamak. Furthermore, the transport of radial electron heat flux is found to be maximizing near the limiter tip location in the poloidal plane.
△ Less
Submitted 27 March, 2025;
originally announced March 2025.
-
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…
▽ More
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.
△ Less
Submitted 8 January, 2025;
originally announced January 2025.
-
Stabilization of sawteeth instability by short gas pulse injection in ADITYA-U tokamak
Authors:
Suman Dolui,
Kaushlender Singh,
Bharat Hegde,
T. Macwan,
SK Injamul Hoque,
Umesh Nagora,
Jaya Kumar A.,
S. Purohit,
A. N. Adhiya,
K. A. Jadeja,
Harshita Raj,
Ankit Kumar,
Ashok K. Kumawat,
Suman Aich,
Rohit Kumar,
K. M. Patel,
P. Gautam,
Sharvil Patel,
N. Yadava,
N. Ramaiya,
M. K. Gupta,
S. K. Pathak,
M. B. Chowdhuri,
S. Sharma,
A. Kuley
, et al. (6 additional authors not shown)
Abstract:
Experiments on ADITYA-U tokamak show a marked enhancement in the sawtooth period by application of short gas puffs of fuel that cause a modification of the radial density profile. A consequent suppression of the trapped electron modes (TEMs) then leads to an increase in the core electron temperature. This slows down the heat propagation following a sawtooth crash, causing a delay in achieving the…
▽ More
Experiments on ADITYA-U tokamak show a marked enhancement in the sawtooth period by application of short gas puffs of fuel that cause a modification of the radial density profile. A consequent suppression of the trapped electron modes (TEMs) then leads to an increase in the core electron temperature. This slows down the heat propagation following a sawtooth crash, causing a delay in achieving the critical temperature gradient inside the q = 1 surface required for the next sawtooth crash to happen. The overall scenario has strong similarities with the behavior of sawtooth under electron cyclotron resonance heating (ECRH). Our findings suggest an alternate, simpler technique for sawtooth control that may be usefully employed in small/medium-sized tokamaks that do not have an ECRH or any other auxiliary heating facility.
△ Less
Submitted 15 August, 2025; v1 submitted 3 January, 2025;
originally announced January 2025.
-
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…
▽ More
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.
△ Less
Submitted 23 July, 2024;
originally announced July 2024.
-
Power exhaust and core-divertor compatibility of the baffled snowflake divertor in TCV
Authors:
Sophie Gorno,
Claudia Colandrea,
Olivier Février,
Holger Reimerdes,
Christian Theiler,
Basil P Duval,
Tilmann Lunt,
Harshita Raj,
Umar A Sheikh,
Luke Simons,
Andrew Thornton
Abstract:
A baffled Snowflake Minus Low-Field Side (SF-LFS) is geometrically-optimised in TCV, increasing divertor neutral pressure, to evaluate the roles of divertor closure (comparing with an unbaffled SF-LFS) and magnetic geometry (comparing with a baffled Single Null, SN) in power exhaust and core-divertor compatibility. Ohmically-heated L-mode discharges in deuterium, with a line-averaged core density…
▽ More
A baffled Snowflake Minus Low-Field Side (SF-LFS) is geometrically-optimised in TCV, increasing divertor neutral pressure, to evaluate the roles of divertor closure (comparing with an unbaffled SF-LFS) and magnetic geometry (comparing with a baffled Single Null, SN) in power exhaust and core-divertor compatibility. Ohmically-heated L-mode discharges in deuterium, with a line-averaged core density of approximately 4x10(19) m-3, are seeded with nitrogen to approach detached conditions. Baffles in the SF-LFS configuration are found to reduce the peak outer target heat flux by up to 23%, without significantly affecting the location of the inter-null radiation region or the core-divertor compatibility. When compared to the baffled SN, the baffled SF-LFS exhibits a reduction in outer target heat flux by up to 66% and the ability to balance the strike-point distribution of heat flux. These benefits are less significant with N2 seeding, with similar peak target quantities (such as heat flux, electron temperature and ion flux) and divertor radiated power. Despite a radiating region located farther from the confined plasma for the SF-LFS than the baffled SN, no change in core confinement is observed. Core effective charge even indicates an increase in core impurity penetration for the SF-LFS. These experiments constitute a good reference for detailed model validations and extrapolations, exploring important physics such as core impurity shielding and the dependence of divertor cross-field transport on magnetic geometry.
△ Less
Submitted 23 November, 2022; v1 submitted 7 September, 2022;
originally announced September 2022.
-
Improved Heat and Particle Flux Mitigation in High Core Confinement, Baffled, Alternate Divertor Configurations in the TCV tokamak
Authors:
Harshita Raj,
C. Theiler,
A. Thornton,
O. Fevrier,
S. Gorno,
F. Bagnato,
P. Blanchard,
C. Colandrea,
H. de Oliveira,
B. P. Duval,
B. Labit,
A. Perek,
H. Reimerdes,
U. Sheikh,
M. Vallar,
B. Vincent
Abstract:
Nitrogen seeded detachment has been achieved in the Tokamak a Configuration Variable (TCV) in advanced divertor configurations (ADCs), namely X-divertor and X-point target, with and without baffles in H-mode plasmas with high core confinement. Both ADCs show a remarkable reduction in the inter-ELM particle and heat fluxes to the target compared to the standard divertor configuration. 95-98% of the…
▽ More
Nitrogen seeded detachment has been achieved in the Tokamak a Configuration Variable (TCV) in advanced divertor configurations (ADCs), namely X-divertor and X-point target, with and without baffles in H-mode plasmas with high core confinement. Both ADCs show a remarkable reduction in the inter-ELM particle and heat fluxes to the target compared to the standard divertor configuration. 95-98% of the peak heat flux to the target is mitigated as a synergetic effect of ADCs, baffling, and nitrogen seeded detachment. The effect of divertor geometry and baffles on core-divertor compatibility is investigated in detail. The power balance in these experiments is also investigated to explore the physics behind the observed reduction in heat fluxes in the ADCs.
△ Less
Submitted 27 July, 2022;
originally announced July 2022.
-
Unraveling diffusion kinetics of honeycomb structured Na$_2$Ni$_2$TeO$_6$ as a high-potential and stable electrode for sodium-ion batteries
Authors:
Jayashree Pati,
Hari Raj,
Simranjot K. Sapra,
Anita Dhaka,
A. K. Bera,
S. M. Yusuf,
R. S. Dhaka
Abstract:
In search of the potential cathode materials for sodium-ion batteries and to understand the diffusion kinetics, we report the detailed analysis of electrochemical investigation of honeycomb structured Na$_{2}$Ni$_{2}$TeO$_{6}$ material using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD) and galvanostatic intermittent titration technique…
▽ More
In search of the potential cathode materials for sodium-ion batteries and to understand the diffusion kinetics, we report the detailed analysis of electrochemical investigation of honeycomb structured Na$_{2}$Ni$_{2}$TeO$_{6}$ material using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD) and galvanostatic intermittent titration technique (GITT). We found the discharge capacities of 82 and 77 mAhg$^{-1}$ at 0.05~C and 0.1~C current rates, respectively, and the mid-working potential of $\approx$3.9~V at 1~C and high capacity retention of 80\% after 500 cycles at 0.5~C as well as excellent rate capability. The analysis of CV data at different scan rates reveals the pseudo-capacitive mechanism of sodium-ion storage. Interestingly, the {\it in-situ} EIS measurements show a systematic change in the charge-transfer resistance at different charge/discharge stages as well as after different number of cycles. The diffusion coefficient extracted using CV, EIS and GITT lies mainly in the range of 10$^{-10}$ to 10$^{-12}$ cm$^{2}$s$^{-1}$ and the de-insertion/insertion of Na$^+$-ion concentration during electrochemical cycling is consistent with the ratio of Ni$^{3+}$/Ni$^{2+}$ valence state determined by photoemission study. Moreover, the post-cyclic results of retrieved active material show very stable structure and morphology even after various charge-discharge cycles. Our detailed electrochemical investigation and diffusion kinetics studies establish the material as a high working potential and long life electrode for sodium-ion batteries.
△ Less
Submitted 1 December, 2021;
originally announced December 2021.