ICTS

In May 2025, the Wendelstein 7-X (W7-X) stellarator set a new world record for the fusion triple product in long-pulse operation, sustaining high-performance plasma for 43 seconds [1]. This result exceeds previous tokamak benchmarks and provides compelling evidence of the stellarator’s ability to achieve steady-state, reactor-relevant plasma conditions. With their inherent stability and continuous-operation capability, stellarators are now emerging as leading candidates for future fusion power plants.
However, realizing this potential requires overcoming key challenges, notably the control of turbulent transport, the suppression of impurity accumulation, and the development of high-temperature superconducting magnets for complex coil geometries. This work focuses on turbulence regulation and the achievement of reactor-grade confinement—central, unresolved issues in fusion research. By building on recent advances [2–4], we outline a clear path toward robust, high-performance stellarator operation and the realization of practical stellarator-based fusion energy.
References :

[1] EUROfusion. (2025, June 4). Wendelstein 7-X sets world record for long plasma triple product. EUROfusion News. https://euro-fusion.org/eurofusion-news/wendelstein-7-x-sets-world-record-for-long-plasma-triple-product/
[2] Singh, T., Nicolau, J. H., Lin, Z., Sharma, S., Sen, A., & Kuley, A. (2022). Global gyrokinetic simulations of electrostatic microturbulent transport using kinetic electrons in LHD stellarator. Nuclear Fusion, 62(12), 126006. https://doi.org/10.1088/1741-4326/ac9b6d
[3] Singh, T., Nicolau, J. H., Nespoli, F., Motojima, G., Lin, Z., Sen, A., Sharma, S., & Kuley, A. (2024). Global gyrokinetic simulations of electrostatic microturbulent transport in LHD stellarator with boron impurity. Nuclear Fusion, 64(1), 016007. https://doi.org/10.1088/1741-4326/ad0e6e
[4] Tiwari, A., Das, J., Alageshan, J. K., Roberg-Clark, G., Plunk, G., Xanthopoulos, P., Sharma, S., Lin, Z., & Kuley, A. (2025). Zonal flow suppression of turbulent transport in the optimized stellarators W7-X and QSTK. Plasma Physics and Controlled Fusion, 67(8), 085025. https://doi.org/10.1088/1361-6587/acdc3f

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This work is supported by DAE-BRNS, SERB/ANRF and NSM. All the simulations are carried out using Param-Pravega at IISc Bangalore and ANTYA at IPR Gandhinagar.

Compact Spherical Tokamaks (STs) offer a unique, low-cost platform to explore low-aspect-ratio plasma physics and technologies that complement conventional high-aspect-ratio devices. At the Institute for Plasma Research (IPR), India’s first compact spherical tokamak has been designed, integrated and commissioned to study non-inductive start-up, current drive in over-dense plasmas, and shaped-plasma behaviour under conditions relevant to future ST-based fusion concepts. The machine has completed major mechanical, magnetic and electrical integration, with first plasma has been achieved.
Compact Spherical Tokamaks (STs) offer a unique, low-cost platform to explore low-aspect-ratio plasma physics and technologies that complement conventional high-aspect-ratio devices. At the Institute for Plasma Research (IPR), India’s first compact spherical tokamak has been designed, integrated and commissioned to study non-inductive start-up, current drive in over-dense plasmas, and shaped-plasma behaviour under conditions relevant to future ST-based fusion concepts. The machine has completed major mechanical, magnetic and electrical integration, with first plasma has been achieved.
This talk will present a few interesting open physics problems in various Spherical Tokamak experiments that are not only relevant for future ST research but also equally important for conventional tokamaks. The talk will conclude with introducing the new compact ST at IPR, highlighting a few preliminary experiments, the first-plasma results, and the near-term opportunities this device opens for students and early-career researchers in low-aspect-ratio tokamak research.

The possibility of a plasma central solenoid spherical tokamak as a fundamental plasma experiment is being discussed.

The talk would give an overview of the parallel private attempts at achieving nuclear fusion worldwide following the routes of (a) magnetic confinement (b) inertial confinement and (c) innovative alternate magnetic confinement methods; since the beginning of this century. It will further list out attractive enroute deep-tech spin-offs applications; some of which have been envisaged and some of which have been realized. The underlying theoretical and technological bases of some of these fusion attempts would also be deliberated in the presentation. Some contextual observations on the role of turbulence playing in the fusion would also be briefly outlined.

Magnetically confined plasmas contain dynamics spanning widely separated spatial and temporal scales, yet these scales are coupled through the geometry and topology of the magnetic field. In this talk I will explore the proposition that magnetic topology provides a useful organising framework for connecting plasma self-organisation, Alfvén-wave dynamics, energetic-particle transport and, ultimately, turbulence.

Relaxed-MHD models provide a natural description of equilibria containing magnetic islands and chaotic field-line regions without requiring globally nested flux surfaces. Recent extensions incorporating flow further suggest that the relationship is two-way: plasma flow can itself modify island structure and magnetic topology. Against this background, I will describe calculations of the shear-Alfvén spectrum in symmetry-broken fields containing islands and chaotic field-line trajectories. Alfvén waves localised on surviving flux surfaces remain comparatively insensitive to the perturbation, while destruction of those surfaces leads to spatial spreading of the wave structure across chaotic regions.

I will then discuss KSTAR experiments and modelling in which resonant magnetic perturbations strongly modify energetic-particle-driven Alfvén eigenmodes. Resonant field penetration changes the magnetic topology, with two coupled consequences: stochastic redistribution of energetic particles reduces the resonant drive, while changes in magnetic shear modify the Alfvén continuum and enhance continuum damping.

Finally, I will consider whether new tools from topological data analysis can provide a common quantitative language for these phenomena. Persistent homology has been used to characterise magnetic-field-line islands and chaos and, more recently, to detect chaos and classify guiding-centre particle orbits in phase space. This raises the possibility of relating quantitative measures of magnetic and particle-orbit topology to wave damping, energetic-particle transport and eventually zonal-flow and microturbulence dynamics. I will conclude with the open question of whether such topological descriptions, together with reduced models of self-organised plasma states, can help expose the feedback loops connecting energetic particles, Alfvén waves, flows and turbulence.

Disruptions is a major obstacle for steady-state operation of tokamak fusion reactors. Moving beyond conventional avoidance or mitigation, this study introduces an alternative approach to actively enhance disruption resilience using 3D non-axisymmetric magnetic fields. In the KSTAR tokamak, we demonstrate a substantial delay in the transition to a disruptive state even in the presence of a destabilizing 2/1 locked magnetic island by applying symmetry-breaking resonant magnetic perturbations (RMPs). Integrating experimental fluctuation diagnostics ECEI with global gyrokinetic simulations using GENE, we reveal that this delay is governed by complex multi-scale interactions among macro-scale magnetic islands, meso-scale self-generated flows, and micro-scale turbulence. Specifically, the applied RMPs induce an auxiliary magnetic island that significantly modifies the self-organized flow structures. This flow modification effectively decreases the turbulence intensity, thereby reducing both the anomalous resistivity and the outward heat flux responsible for the thermal quench. Consequently, harnessing these multi-scale dynamics via 3D magnetic fields offers a novel strategy to overcome disruption limits, providing a robust pathway toward sustainable, high-performance fusion operations.