Small-Scale Spherical Tokamaks: Compact Catalysts for Fusion Innovation

For decades, fusion energy has stood as the ultimate prize in clean energy—a virtually limitless power source without carbon emissions or long-lived radioactive waste. While large-scale projects like ITER aim to prove fusion at scale, a growing wave of small-scale spherical tokamaks is reshaping the path toward practical, compact, and faster-to-deploy fusion devices.

These smaller systems pack powerful physics into tight geometries and are rapidly becoming the testbeds for next-generation fusion science and engineering.

🔄 What Is a Spherical Tokamak?

A spherical tokamak is a type of magnetic confinement fusion device that modifies the conventional toroidal (donut-shaped) design into a tighter, more compact geometry resembling a cored apple or rugby ball.

This geometry offers key performance and engineering benefits:

• Higher plasma pressure (β) relative to magnetic field

• Improved magnetic efficiency and stability

• Smaller footprint and lower cost of construction

This design enables exploration of advanced confinement physics with fewer materials and lower infrastructure needs—ideal for innovation and experimentation.

⚙️ Why Go Small?

Unlike megaprojects that take decades to realize, small-scale spherical tokamaks are:

• ✅ Affordable – Significantly lower construction and operating costs

• ✅ Fast – Ideal for quick iteration and experimental upgrades

• ✅ Flexible – Perfect for academic labs, startups, and research institutes

They allow researchers to rapidly develop, test, and validate new technologies—like AI-driven control, novel materials, and compact magnet systems—without waiting for billion-dollar timelines.

🛠️ Engineered by RANVAC Technologies

This particular system was designed, manufactured, and installed by RANVAC Technologies, Bangalore, a leading engineering firm specializing in high-vacuum and precision plasma systems. The fully integrated spherical tokamak system was supplied to the Institute for Plasma Research (IPR), Gandhinagar, one of India’s premier institutions advancing fusion energy research.

Their collaboration represents a significant step forward in indigenous development and deployment of advanced fusion infrastructure. The vacuum chamber and assembly had very tight tolerances in less than 100 µm dimensionally and less than 5-10 µm in the all the critical internal part facing surfaces. The chamber was electropolished to achieve less than 1.6 µm RA finish.

🔍 Technical Highlights

📏 Mechanical & Structural Overview

• Total Height: 3000 mm

• Overall Width: 2100 mm

• Center Bore Diameter: 160 mm

  • Machining Tolerance: < 5 µm

• Vacuum Vessel Height: 760 mm

• Vacuum Vessel Diameter: 1040 mm

• Material: SS 304 Stainless Steel

• Ports: 6 radial, 6 top, 6 bottom

• Vacuum System:

  • 2 turbo pumps at bottom ports

  • Base Pressure: 5 × 10⁻⁸ mbar (after baking)

🔥 Baking & Wall Conditioning

• Baking: 150°C for 48 hours

• Glow Discharge Cleaning (GDC):

  • System current: 1 A

These steps ensure ultra-clean internal surfaces, minimizing plasma contamination and maximizing reproducibility.

💨 Gas Feed System

• Working Gas: Hydrogen

• Injection Method: Piezo-electric valves

• Gas Throughput: 6 t·l/s

🔁 Magnetic Coil Configuration

🧲 Central Solenoid Coil

• Quantity: 1 – provides plasma initiation and drives current

🧲 Toroidal Field (TF) Coils

• Quantity: 6 – generate the magnetic cage around the plasma

🧲 Poloidal Field (PF) Coils

• Quantity: 3 sets (up/down) – shape and stabilize the plasma column

🧲 Compensating Coils

• Quantity: 3 sets (up/down) – balance and fine-tune magnetic symmetry

  
  

🌐 A Platform for High-Impact Fusion R&D

This machine is not only a fusion experiment—it is a research enabler. Designed with modularity and precision in mind, it supports:

• Plasma shaping and stability studies

• Wall material testing under real plasma conditions

• Real-time control algorithm development

• Training and capacity building in fusion tech

Its successful deployment at IPR demonstrates the viability of homegrown, high-performance fusion platforms in India.

🚀 Looking Forward

Small-scale spherical tokamaks are proving to be agile, cost-effective, and scientifically rich tools in the race toward fusion energy. The system designed by RANVAC Technologies and delivered to IPR is a testament to the power of industry-academia collaboration in accelerating progress.

As the global community strives for fusion electricity, these compact reactors will continue to play a pivotal role in exploring the frontiers of plasma physics and applied fusion engineering.

For collaboration opportunities on plasma systems or developing ultra-high vacuum chambers and systems, please contact RANVAC Technologies at sales@ran-vac.com or +91 8050569933

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