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In Conversation With a Scintillating Nuclear Physicist

Maitreyee Saha Sarkar deals with work on nuclear structure to understand why various nuclei at the hearts of atoms behave in different ways.

Maitreyee Saha Sarkar. Credit: Author provided

Maitreyee Saha Sarkar. Credit: Nandita Jayaraj/TLoS

The nucleus of an atom is tiny – only a few femtometers in size (10^-15 metres) – and the forces that hold it together are very strong. This means it’s a heck of a task to study them. “Only a very highly energetic particle can go very close to it,” said Dr Maitreyee Saha Sarkar, head of the nuclear physics department at Saha Institute of Nuclear Physics (SINP) in Kolkata. “And that’s why to do good research in nuclear physics, you need an accelerator”

The mention of “nuclear” tends to first bring to mind nuclear power or nuclear bombs, but Sarkar deals with something much less controversial and much more fundamental. “I work on nuclear structure to understand why various types of nuclei behave in different ways; when ‘excited’ they usually emit gamma rays, other times they may even break!”

A nuclear physicist’s favourite tool is the accelerator. Zooming inside an accelerator, are bare nuclei (atoms minus the electrons). The nuclei collide and the resulting interactions are helpful to investigate the structure and properties of the nuclei. Sarkar has spent much of her career gathering clues in this way.

Exotic and enigmatic

Nuclear physicists like Sarkar are most intrigued by what they call ‘exotic’ nuclei. These refer to the less stable forms or ‘isotopes’ of an element -for example, oxygen-16 (8 protons + 8 neutrons) is the most common and most stable isotope of the oxygen atom, but there also exists other isotopes of oxygen like oxygen-17 (8 protons + 9 neutrons) and oxygen-18 (8 protons + 10 neutrons). “When we were young, we studied only these three – all are fairly stable – but now, with new accelerators and new machines, we can study more exotic nuclei such as oxygen-13, which is very unstable.”

An atom is made of a central body called a nucleus (containing positively-charged protons and chargeless neutrons) around which hover negatively-charged electrons. We have advanced greatly in our understanding of atomic structure but one great mystery that remains is the nucleus itself – we are yet to completely make sense of what goes on inside it.

Even with accelerators at their disposal, a holistic picture of the nucleus remains elusive. Sarkar drew an analogy to the fable of the blind men and the elephant – “in the story, each man touches different parts of the elephant and uses what he felt to describe the whole elephant. Similarly in nuclear physics too, we’re doing more of phenomenology…”

Credit: Author provided

Credit: Nandita Jayaraj/TLoS

Nuclear – a ‘known’ hazard

Exotic nuclei are often radioactive so registered radiation workers like Sarkar need to comply with safe practices such as gloves, radiation badges and sometimes bodysuits. These are essential accessories for a professional like her. The radiation badges record how much radiation its wearer is being exposed to. “Those counts are sent to places like BARC where they are checked to make sure they are within permissible limits.” Bodysuits become essential when working with accelerators but for radioactive sources in labs these are not needed, she added.

Sarkar fully understands that these precautions are necessary and tries her best to ensure that her students follow them too. “Even though our lab has nothing very hazardous – our samples are all shielded by lead blocks so even the walls would be emitting more radiation than that – I tell them to always wash their hands, even if they have not touched anything. It’s like the helmet issue – you wear it for your head, not for the police.”

This high level of regulation in the nuclear sciences is what makes Sarkar think that the anti-nuclear energy sentiment is not always warranted. “Working in this field, I know how much care we take of everything. For thermal power, you burn coal – do you know how much heat hazard that is? When burning coal, you end up leaving uranium and thorium radioactivity in the air. There is no measurement for any of that, but with nuclear energy, measurements are done regularly. It is more of a ‘known hazard’.”

From annoyance to passion

Having worked at SINP since her PhD days, Sarkar considers it the place she was “born and brought up” in. But she says her foray into nuclear physics was not at all intended. She did her BSc and MSc in Physics at Presidency College and Calcutta University respectively. “I didn’t like nuclear physics. In fact, if you had told me that I would end up working in this area I would have said that you have the most absurd imagination!” she said, laughing. She applied to SINP for a PhD because it was prestigious and it had other areas of physics too.

“Nowadays people plan so much and at such early stages! But my only plan was to do experiments,” In Sarkar’s view, doing experiments involves more intuition than theoretical work. “To know what exactly to do in a situation, you need more presence of mind. I was always amazed by good experimentalists, so I thought I too have to do this.” She started work in condensed matter physics but when her guide got a new job, she was advised to shift to another area. This was when she met a professor in nuclear physics who was such a good teacher that it made her decide to pursue the subject that once used to ‘annoy’ her.

Dealing with gender imbalance

Her college education in physics was male-dominated, she conceded. “But in my BSc class, the first ten ranks were held by girls. There were a lot of serious girl students. I used to go up to the boys and say ‘Hi, I’m studying in your class’. And they would get nervous!” she laughed.

“My upbringing was like that. My parents gave me a lot of freedom and I never felt any different because I was a girl.” Her father often took her to political meetings. “I don’t know why but I really enjoyed them,” she fondly reminisced. At her home, she clearly recalls her mother, an economics teacher, would be the go-to person when the bulb fused or when the heater coil needed to be changed. “It was natural in our family that our mother did these things. Maybe that influenced me…”

Credit: Nandita Jayaraj/TLoS

Sarkar talked to me about how she and her classmates handled an unpleasant episode during her BSc. “One of our chemistry teachers – a young faculty at the time – he used to say very abusive things to girls. He used to say that our only purpose was for decorating the class.” The girls complained to the head of the chemistry department and when he refused to take any action, they tried their luck with their own HOD (of the physics department). “The head at the time was the very respected Prof Amal Kumar Raychaudhuri. He was so nice. He told us that he knew some men are like this because his own daughter was studying medicine and similar things had happened. He agreed it was unfortunate and that such things must not happen, but he could not interfere either.”

But Sarkar suspects that Prof Raychaudhuri did after all have a chat with the abusive young lecturer. “He later became so friendly to us. He used to take us to the coffee house, pull us to the canteen… I met him just a few years back – he became a vice chancellor of a university.”

 In my home, my mother used to be the one who changed heater coils, replaced bulbs… It was natural in our family that my mother did these things. Maybe that influenced me.

Sarkar’s fight-back spirit aided her even as she went further in her career. “While working at the neighbouring Variable Energy Cyclotron Centre (VECC), I was the only lady in a boys group. In the evening, they used to shut the ladies toilets so I had to come to SINP to use the toilet here. In the first month, I was hesitant [to take this issue up]. But later I became confident. I told them to keep it open. These things trained me a lot. I spoke my mind more. I could not afford to be shy!”

Today, SINP has three women among its heads of department. Sarkar points out that they are all in the experimental side; unfortunately, no women head the theoretical departments currently. “See there’s nothing like girls cannot be good experimentalists. In Saha, from its earliest days, many faculty members were women…”

The future of nuclear physics

SINP was inaugurated by Nobel Laureate Irene Joliot-Curie in 1950. And those, according to  Sarkar were nuclear physics’ most glamorous days. Studies in this field involve expensive equipment that was in the beginning, only affordable to national institutes. This changed with the setting up of the Inter-University Accelerator Centre (IUAC) in Delhi which enables accelerator-based research in universities. “This generated a new batch of people who got trained in accelerator physics,” said Sarkar. “Those people became experts in nuclear physics and took their expertise back to universities, where they took in new students.”

But the last decade or so is seeing a decline in interest in this basic science. Sarkar is concerned that though students are interested in her field, job opportunities are scarce and many top research institutes like the IISERs have no nuclear science departments. “I feel really bad because many students don’t get nuclear physics jobs. Most end up as high energy physicists working in international collaborations.”

But that is like working in a big factory, according to her. “You have a specific duty, they will not allow you to do everything, to know about everything. So students working there from the beginning do not get hands-on experience. They call themselves experimentalists but they do not even know to tell apart a 5 ampere plug from a 15 ampere plug. People like us still exist, but in 10 years this group will slowly diminish unless you create another set of people.”

So why has nuclear science lost its shine? “At the moment, we have many people in the field but no father figure… usually in India you need one,” she mused. “The hype around subjects – like right now there is hype around biotech and nanoscience – depends on how many big shots there are. In material science, C.N.R. Rao is there, high energy physics has Bikash Sinha (former director of the institute) – so these fields get lots of people, but nuclear physics doesn’t have that one great person. Meghnad Saha was there long back, but now nuclear physics is slowly diminishing.”

However, Sarkar is not one to let this scenario defeat her. After decades of research at SINP, she now finds herself getting increasingly involved in graduate student projects. Her students come from all over the country – most, from institutes that do not have access to nuclear physics facilities themselves. “Yes, I take these projects very seriously. I like working with them. Small, small things that PhD students cannot do because of the strict time limit, these students can. Every year, I take up almost 10 students. They are very young, very inquisitive – they don’t have any preconceived notions, so I can also think a little… absurdly,” she laughed.

The price of delayed projects. Credit: Nandita Jayaraj/TLoS

Sarkar is one of the many physicists disheartened by the delay of big fundamental science projects in India. The India-based Neutrino Observatory (INO) which has been in the pipeline for over a decade is one famous example.

“If the INO happens, it will be good. I think a lot of people were recruited in the hope that they will be permanent. If you delay a project, the cost goes up and interest goes down. This happened in our institute also. Around 10 years back we bought a small accelerator intended for nuclear astrophysics studies – it was state-of-the-art, we had international people coming in, workshops, interactive sessions… In 2010, it was delivered. It was supposed to be set up in the New Town area Kolkata, but then government change took place. After the Singur and Nandigram incidents, there was a lot of resistance from the government. They did not allow us to put the electrical work and land acquisition issues came up. Everything stopped.

So we decided to leave that place and have it here on campus instead – but here it is  cramped. There was a lot of turmoil in that time and we had to forget our expansion plans. It was supposed to be completed last year. When we made plans for this, we were all younger – in our 40s and 50s – we had 10 years ahead of us. By the time this is finally installed, many of us primary people will be retiring.”

This piece was originally published by The Life of Science. The Wire is happy to support this project by Aashima Dogra and Nandita Jayaraj, who are travelling across India to meet unsung women scientists.