Starting in 1983 at Lawrence Berkeley Laboratory (and Univ of California, Berkeley) till 2002, I did full-time research in the area of Nuclear Fusion in USA and India. I contributed through modeling, development of data acquisition and control system, variety of system development, experiments, and operational improvements as well as solving technical problems to enhance the performance of both the first generation Tokamaks(a type of Nuclear Fusion Reactor) in Saha Institute of Nuclear Physics(SINP), Kolkata and Institute for Plasma Research(IPR), Gandhinagar to international levels of performance. At IPR, I was project leader of Aditya Tokamak from 1996 to 2002. I was also Project Leader of SST-1(Superconducting Tokamak) Operation and Control Group from 1997-2002.
Here I describe my contribution during the continued contribution to Nuclear Fusion for almost 4 decades.
How I got into Nuclear Fusion Research – This blog talks about my sudden decision to change the plan of my research field from Astrophysics to Nuclear Fusion, when I was about to leave the country at midnight to go to Univ of California, Berkeley so that I could serve the nation better after coming back.
Table of Contents
PhD Thesis (1983-86) – Lawrence Berkeley Lab/Univ of California, Berkeley
• New Nuclear Fusion reactor design concept – Triangular Helically Linked Mirror Arrangement -This new concept was a hybrid of magnetic mirror concept and stellarator. Copy of thesis is available at: https://www.osti.gov/servlets/purl/7008679
Saha Institute of Nuclear Physics, Kolkata (1986-95)
I carried out Modelings and Simulation, developed Data Acquisition System, Discharge Cleaning System to remove impurities, Slow Bank Power Supply system to keep the plasma current flat for 20 ms, Modified Gas puffing system and other modifications and improvements to make the first Nuclear fusion reactor in India, SINP Tokamak operate as per International standards over a period of 1987-93.
Details of these have been shared in my blogs:
• Successfully developed PC based data acquisition system for SINP Tokamak in 1987 using GPIB interface. Without this proper analysis of experimental data would not have been possible. This was among the earliest development in the country along this line. See blog How Japanese got hooked on to Indian technology!
To carry out the task of modeling and simulation, I had to initiate and work with institute authorities to get computer systems installed in the institute, which was done in 1987. Following this, codes (including transport code BALDUR with 60,000 lines) were ported and run to understand Tokamak behavior. New customized codes were developed with successful understanding.
• On the basis of computer modeling, I could correctly identify impurities as a major problem impacting the performance of the machine. Since no experimentalist was coming forward, I developed a unique Audio-frequency discharge cleaning system ( 90 kW, 2.5 KHz pulsed power) resulting in miraculous improvement in plasma as per expected international norms. See details in my blog How I became Accidental Experimentalist !
• Since the machine did not have a power supply system to maintain the plasma current at peak (“flat top”) due to budget issues, I developed a Slow capacitor bank power supply system for extending plasma pulse (200 kJ, consisting of nearly 1300 large electrolytic capacitors and automated control) to designed 20 ms flat top at a low cost of Rs 20 lakhs compared to Rs 1.5 Cr quoted by TOSHIBA. This also required me to redesign and reconfigure the existing power supply to better the performance.
• All these steps and many other operational changes led to achieving the full designed parameters (75 kA, reproducible plasma) of SINP Tokamak (around 1993)
As I got more experienced, I started to plan for a Superconducting Tokamak to move towards a much longer pulse length. I discussed with Prof Kaw(Director, IPR) and other senior scientists and they supported this project. As VECC was planning a superconducting cyclotron, it would have led to sharing our expertise and resources on the same campus.
However, in 1994, IPR got a go-ahead from Govt of India for the superconducting Tokamak project ( a series of two machines: SST-1 and SST-2). Following this IPR was moved from DST to DAE to be able to handle larger budgets etc. IPR Governing Board approved the invitation for me to shift to IPR to participate in this project.
Institute for Plasma Research(IPR), Gandhinagar (1995-2002)
Proejct Leader, ADITYA Tokamak
• After joining IPR in 1995, with changes made in the operation of the machine and development of Pulsed Discharge Cleaning, Microwave Discharge cleaning and numerous other modification, I was able to bring about a dramatic performance improvement in ADITYA Tokamak discharges (with pulse length improving from 30 ms to 220 ms, plasma current going above 110 kA, reproducibility improving from 15% to 80-90% and many other improvements). Furthermore, major weaknesses limiting the performance of the machine were solved providing scope for better exploitation of the machine. All the subsystems developed for the machine were allowed to go on the machine.
Details of some of the important events during this phase are given in blogs below:
5 Days Miracle in Nuclear Fusion Reactor(ADITYA Tokamak) – This blog describes how ADITYA Tokamak(made operational in IPR in 1989) used to have plasma current crashing in rising phase within first 20-30 ms, making any useful experiments impossible and keeping plasma parameters low. By operational modifications in power supply, I could change this in 5 days time after joining in 1995 and improve the plasma parameters so that it did not crash in rising phase after 6 years of first plasma. After this, I was given the responsibility of the Project Leadership of ADITYA Tokamak in early 1996.
Rural technology helps fusion reactor! – The following blog describes the failure of about 80% of the discharge as power supply control detected anomalies. I could discover this to be linked to improper maintenance of the grounding system and found a way to improve the grounding system and thus discharge failure was removed completely.
How a “Photo” brought ADITYA Tokamak(Nuclear Fusion Reactor) back from death! – This blog describes the insulation failure in the central solenoid(TR-1) of ADITYA around 1997-98 that was embedded in the middle of the machine. Taking this out and repairing it would have required disassembling the whole machine and reassembling it again – leading to downtime of 2 years or so. I found a way to take out TR-1 without any significant disassembly and repair it and put it back quickly. TR-1 used to have weak insulation of about 7-8 KV compared to the design requirement of 20 KV. After this repair, insulation was improved to 20 KV and this set the path for raising the machine to higher parameters and performance.
Successful design and implementation of PC based control using Real Time Linux for Aditya Pulsed Power System of 60-70 MW with 1 ms loop. This was done around 1999 and was the World’s largest power supply being controlled by Real Time Linux. It led to change over from old out of service PDP-11 based control system so that machine could continue to operate without interruption.
Mystery of Error Fields in ADITYA Tokamak(Nuclear Fusion Reactor)! – ADITYA magnetic field mapping had revealed the presence of relatively high errors in magnetic fields inside the vacuum vessel (roughly 30-40 G at a minimum compared to expected Zero.). This blog describes how this mystery was resolved and attributed to changes in magnet coil design due to manufacturability issues. I could predict this from magnetic field calculations before TR-1 coil was removed but confirmation of the change in length from 100 cms to 107 cms could be done after removal. Thus mystery of magnetic error field was solved.
Dancing Sparks in ADITYA Tokamak(Nuclear Fusion Reactor) – The following block describes sudden sparks being noticed in ADITYA that were not related to any insulation failures as we moved to higher parameters. Eventually, this was pinned down to improper grounding of different segments of the machine. By redoing the complex grounding system in a methodical way, the ground faults were identified and corrected. This allowed further raising of parameters and higher machine performance.
Sudden Silence in ADITYA Tokamak(Nuclear Fusion Reactor) – As we moved to higher parameters, due to the failure of the power supply safety system, there was a major accident in the machine and it led to the breaking of restraining support system and two big magnets being thrown out along with fire and many damages etc. A systematic investigation led to wrong assumptions of forces at the time of design that led to weak restraining system design. This whole thing was redesigned and this led to the removal of another major weakness of the machine in achieving higher parameters. After this machine became ready for moving towards high parameters and we could start to get a discharge duration of 220 ms or so as well as a higher plasma current.
(This meant that I had the unique privilege of bringing the performance of both the first generation Tokamaks in India to international standard)
Project Leader, SST-1 Operation and Control Group
As Project Leader of SST-1 Operation and Control Group, my design of control system based on Distributed control using Reflective Memory concept based on digital system (designed in 1998-99) has been followed by many Tokamaks including upcoming International Tokamak, ITER.
Dhirubhai Ambani Institute of ICT, Gandhinagar (2002-2013)
After moving here, my scope of research widened in many different areas including the Chandrayaan-2 mission, Disability Sector, Wildlife etc. However I continued to work on projects related to Nuclear Fusion: (1) Sensor Networks for Tokamak, (2) Miniature Imaging camera for Tokamak (3) RF Energy harvesting inside Tokamak to power sensor network nodes (4) Optical Communication based Wireless Sensor Network Design for Tokamak
TIFAC, New Delhi (2013-18)
As Head of India’s Technology Think Tank, TIFAC, I was keeping an eye on Technology Developments taking place in the Nuclear Fusion sector. Due to very high magnetic field coils based on High-Temperature Superconducting(HTS) Magnets, possibilities commercial use of Fusion appeared to come closer. Based on this, I started to put this possibility in National Level policy documents such as Technology Vision 2035.
D Y Patil International University, Akurdi, Pune (2018 onwards)
For the first time in the country, I have started a Nuclear Fusion Technology Development program with the help of Private Investments called Project Sanlayan. Initial funding is from Silicon Valley. Our plan is to develop a Compact modular Nuclear Fusion based Neutron Source that can be used to produce Medical isotopes, Fissile Fuel, Processing of Radio Active waste and eventually Energy production. This project was announced on Dec 3, 2020 during 8th Bihar Science Conference Nuclear Fusion in India : Past, Present and Future
For nearly four decades, I have been involved in the Nuclear Fusion work due to a midnight patriotic feeling while on my way out of the country for higher studies and since then have continued to play a role in developing or promoting nuclear fusion in India. I hope to continue contributing to this and expect to see applications happening in India too!