5 Days Miracle in Nuclear Fusion Reactor(ADITYA Tokamak)

[This blog describes how I could get ADITYA Tokamak working in 5 days in 1995 in spite of international experts failing to do so for 6 years!]

After doing my PhD in Nuclear Fusion area in Berkeley, I returned to India in 1986 and joined Saha Institute of Nuclear Physics(SINP), Kolkata. Read about them in my blogs :

in 1990-91, I could improve the SINP Tokamak to international standards based on the work described in blogs above. We used to have annual plasma science conference(PSSI Symposium) in different cities. In 1991, it was held at CAT, Indore(Now called RRCAT). Institute for Plasma Research(IPR), Gandhinagar is the main Nuclear Fusion research centre in India. IPR had major influence on the Annual PSSI Symposium since it used to give a generous grant for the event as well as most of the key positions were held by IPR.

I felt that I needed to report my work to the plasma science community during the annual symposium at Indore and sent a mail to organizers saying that I had some very interesting results from SINP Tokamak to report and would request for some time to be given to me for this purpose. Organizers generously allotted 1 Hour for my talk in a session on Tokamak and was followed by talk on ADITYA Tokamak(operational in IPR) in same session. Couple of my colleagues, who were also presenting papers at the same conference, came to me and wanted to use time slot allotted for me to give talks on their papers too. I agreed to share the time slots equally and asked them to speak first and let me speak in the last 20 minutes. After I made my presentation about improved performance in SINP Tokamak, next presentation was on ADITYA Tokamak. However speaker avoided talking about ADITYA Tokamak performance since it would have led to comparison between the two machines as ADITYA was not performing well at that time. Immediately after the session, Director and Dean of IPR asked for a meeting between IPR team and SINP team. From SINP side there were no senior persons present and so only 3 of us participated. Discussion was held to start collaboration between the two groups (IPR and SINP) working with Tokamak. During this symposium, I was also asked to become Editor of PSSI Newsletter, which I remained for next 4 years.

(Frankly speaking, it should have been done since long. IPR was started by funding from DST and SINP project was funded by DAE. There was usual rivalry between the two programs. IPR was at much larger scale since a whole institute was created for this purpose and planned as the main Nuclear Fusion research Centre for India. SINP Tokamak was fabricated by TOSHIBA as per specification given and delivered in 1987. Couple of Japanese engineers had come to install the machine, which took few weeks. It became operational some time in Aug-Sept 1987. However no one from IPR visited to see what was going on, may be thinking it to be not useful!)

As part of the collaboration, exchange of Scientists was planned and I was requested to kick start by coming to IPR for 2 weeks or so, which would be followed up by a scientist from IPR visiting SINP. I managed to visit IPR for two weeks some time in May-June 1992. I already knew most of the scientists in IPR since we would meet during annual symposium etc. I was suggested that I should submit a paper for IAEA Small Tokamak Workshop planned in Germany based on my work on SINP Tokamak. Paper was accepted and financial support was provided to attend the meeting. Along with this, there was main IAEA conference on Nuclear Fusion too. I also went to Brazil in 1993 to attend IAEA Small Tokmak workshop.

After successfully improving SINP Tokamak, I was planning the next generation Tokamak in the form of Superconducting Tokamak. VECC, Kolkata(an Unit of BARC, with whom SINP shared campus) was working on a superconducting cyclotron project. I felt that we may be able to share resources and expertise to make this feasible. In Brazil, we were taking an after dinner walk with a beautiful night view (as the conference hotel was on a hillock) along with Prof P K Kaw and others. I mentioned about my plan for superconducting Tokamak. He heard it and said that I should go ahead and they would support it too. I had heard that IPR also wanted it but Govt agencies were not willing to support since first IPR Tokamak, ADITYA was still not operational properly. Prof Kaw suggested to have a joint workshop of SINP and IPR to collaborate. I agreed and some time in April or May, we had a joint workshop in IPR. Few of us were travelling from Kolkata to Ahmedabad in train and it used to take about 48 hours. I was working on my Superconducting tokamak plans during the journey and preparing for the talk.

On the morning of the meeting, Prof Kaw got up to welcome the gathering. But surprisingly, he announced that they have got go ahead from Govt for two Superconducting machines at budget of Rs 800 Crores. I was completely taken aback since I was wanting to make a pitch for superconducting machine in Kolkata and we had traveled all the way to discuss this! Later on I was suggested that I could move to Gandhinagar and participate in the project. After discussing with my family, I decided to move to IPR. IPR had a system to invite some reputed scientists to join by invitation instead of usual process of advertisement etc. This had to be first approved by Governing Body. Due to this major project coming along, IPR was moved from Dept of Science and Technology(DST) to Dept of Atomic Energy(DAE). This process took some time and eventually I moved to IPR in Aug 1995.

After joining, I met Prof Kaw to discuss my responsibilities. He told me to work on ADITYA. I was bit surprised since I had been invited to work on SST-1, Superconducting Machine. ADITYA had become operational in late 1989 with an alternate small capacitor based power supply. Main power supply (ADITYA Pulsed Power Supply, APPS) was being integrated in the meantime. Performance of ADITYA had not improved much with discharges crashing in about 20-30 ms while the plasma current was in rising phase. Normally one expects plasma current to rise and reach a peak value, where it is maintained (called “flat top”) for experiments to be conducted. I was aware of all the effort that was put by IPR, specially Prof Kaw with his international links, by getting international experts and spending time with ADITYA. Given this background, I was bit hesitant to put my hands on ADITYA. So I mentioned to Prof Kaw that I was called for SST-1 and he said you share the time between the two machines. I agreed to that and discussed with one of the senior scientists, Dr Jha,  to get more technical details of ADITYA. I recall that it was annual night at IPR and I was sitting with Dr Jha and discussing machine details in his office.

After couple of days, Prof Kaw was returning from lunch (he used to take lunch in canteen only) and my office was on the way. He asked me if I could figure out something about ADITYA. I mentioned to him that I would like to try out few things. He told me to make a presentation in the weekly Monday morning of ADITYA. I made a presentation by giving plans of what all things I wanted to try out. Prof Kaw asked the team looking after ADITYA to give their comments. They mentioned that whatever I am telling is not new and they don’t help. He said in any case it is not working so what’s the harm in letting him try. But almost 3 months passed and I was never given chance to work on the machine. In the meantime, I also went through the details of program of power supply(APPS) control system running on a PDP-11 machine to understand its working. I got fairly good idea and realized that we were not using the full control features of the machine based on the feedback mechanism. Rather it was being used in manual testing mode with no feedback being used.

Around some time in Oct-Nov 1995, there was annual plasma symposium, possibly in Allahabad, where during lunch time, I was sitting next to Prof Kaw. He mentioned to me that he was told that my ideas for ADITYA were tried and they do not help. I expressed my surprise by saying that I am not aware of any such efforts since I was never informed even though i was very much around all the time. After few days(probably a Friday), when we were back to IPR, he called me to say that ADITYA Project leader was going to be out of country for few weeks and I should try out my ideas.

On Monday and Tuesday, I went to power supply control room and tried to adjust few parameters mainly to slow down the rise of current in one of the set of magnetic field coils (“vertical field”) as I felt that it was rising too fast and pushing the plasma current to crash. It is supposed to keep the plasma centered by managing  appropriate component of the magnetic field. On Wednesday, I met Prof Kaw at lunch time and mentioned to him that I am going to try out a change of strategy. Existing effort was on making plasma current rise fast to about 100 KA and then maintain it at that level. In the process, it used to crash much before it reached that value. I told him that I would target smaller currents like 50-60 kA and try to maintain it for longer period of time and achieve a flat top. Once I achieve this, I would try to go for higher current. He told me that it is my call and I was free to make my decision. Having obtained a go ahead from him, I started adjusting parameters as per my strategy. On Friday, we noticed the first such discharge which lasted for much longer time (may be 70-80 ms) without crashing in the rising phase. Rakesh Tanna, who was Scientific Asst at that time as well as a avid cricket player, used to sit in the control room with microphone and used to make announcements about the discharge. He made the announcement – “Shot of the Century!”. We used to call each discharge as “Shot” and they were numbered consecutively and recorded in the log book. It is difficult to recall now but this may have been a shot number 3700-3800. There was clapping all around.

After 6 years of wait, 5 days miracle had happened and ADITYA had entered into a new phase of operation!

I could have stopped this story here itself but I would add some additional parts to complete the story.

Most of the diagnostic systems, which allow Scientists to observe detailed data inside the very hot plasma (running in to millions of degrees, were not put on the system due to machine not performing well. However now there was no reason to delay that and it was decided to open the machine (mainly the vacuum system) for installation of various diagnostics. One critical diagnostics is Soft X-Ray measurement system. Along with the lead scientist, Dr CVS Rao, responsible for the development of this system, I had travelled to SINP, Kolkata and tested this system to work on the SINP Tokamak. This diagnostic was also installed on ADITYA after machine was opened. In fact many of the Scientists had worked for years to develop their systems but were frustrated in not being able to connect their systems to the machine.

While all this was going on, suddenly I came to know about loss of my Grandmother in Dec 1995, with whom I was personally very close. I rushed to my village in Bihar due to this and returned after about 2 weeks and came straight to office from Railway Station in the morning. After reaching office, I was told that ADITYA vacuum vessel had been closed and diagnostics were installed but machine was again not working well. I remember, it was Thursday and i went to the control room to see what had happened and if installation of additional systems had indeed affected the machine performance, which was being suspected. I worked there and by Friday afternoon, machine was back to performing well again. With additional diagnostics installed, we started getting more information about the plasma parameters.

One of these was information about plasma temperature through Soft X-Ray data, which we had tested to work in Kolkata, few weeks earlier. After I could adjust ADITYA parameters to get longer discharges, we also started to notice Soft X-Ray signals indicating that plasma temperature was getting higher and higher. After few discharges, we also started to notice sawtooth oscillations, in the plasma. This shows plasma temperature going up slowly in the center and then suddenly dropping and then again rising. This slow rise and fast sudden drop resembles a Sawtooth – thus this name! It is standard behaviour of any Tokamak plasma and one IPR scientist, Dr Avinash, used to say that Sawtooth oscillations indicate that plasma is breathing and is alive! So finally ADITYA had come alive!!!

I went to Prof Kaw’s office to share the good news. However I was told that he is in a Workshop in Ahmedabad along with most of the senior scientists for a 4 week winter school. I requested his staff to send a message to Prof Kaw in the form of a cryptic message that “Sawtooth Oscillations were seen in ADITYA”. This was year 1995 and there was no mobile phone etc in India had just started with access to very few people and there was no choice except to connect using landlines. The message was communicated to reception of Sterling City resort, where the workshop was going on. A small paper chit with the message was passed on to Prof Kaw in the meeting room. This was the last day of the workshop and by the time message reached, it was almost over with participants having tea coffee etc before dispersing. As the chit was making its way to Prof Kaw, it came in the hands of Prof Sen, Dean of IPR. He saw the message and instead of handing it over to Prof Kaw, he read it out loudly announcing it to everyone present in the room. There was jubilation in the room with clapping etc. One of the senior scientists, Dr Bora, made a cryptic remark – “Prabhat Ranjan must have come back!”.

This led to some heartburn among few scientists too and next week many expressed their displeasure in variety of ways. I was accused of interfering with the machine operations and saying that it was not my job.

Towards end of December 1995, a very high level review team had come to review IPR since it was setup by funding of DST at about Rs 25 Crore. It was a two day review process. Prof Kaw right in the beginning announced the improved performance of ADITYA and mentioned my name along with it. Towards the end of day, I was asked to take the review team to ADITYA and explain the details. Review team was trying to be very critical and was asking me lots of questions trying to be critical. I answered all of them in very cool manner without loosing my temper or patience! Among the team were many senior scientists from BARC. Since SINP was funded by Dept of Atomic Energy(DAE), which also funded BARC, they felt that I was part of their fraternity and made the comment that someone from DAE had to come to get ADITYA working!

In the annual report of 1995-96, Prof Kaw wrote very happy remarks talking about superb performance of ADITYA etc. However he did not mention operational changes here. After few weeks ADITYA team was reorganized and I was made Project leader of ADITYA some time in Feb-March 1996 reporting to Director. Subsequently I was also given responsibility of SST-1 Tokamak Operation and Control Group as its project leader. I was given few more responsibilities and was responsible for seven different groups at one time.

In 2002, I moved out of IPR to Dhirubhai Ambani Inst of ICT(DA-IICT) in Gandhinagar. I would be sharing few more experiences of my seven years of stay in IPR in other blogs. Some of these are:

https://ranjan.inrural-technology-helps-fusion-reactor/

https://ranjan.inhow-a-photo-brought-aditya-tokamaknuclear-fusion-reactor-back-from-death/