Ryan Howell [00:00:58] Welcome back, everybody. This is another episode of Titans of Nuclear. My name is Ryan Howell, and I have the privilege today of speaking with Dr. Sharmistha, and I'm going to let you pronounce your last name so I don't mess it up.

Sharmistha Mukhopadhyay [00:01:09] Mukhopadhyay.

Ryan Howell [00:01:11] Mukhopadhyay, yes. Thank you very much for joining us today.

Sharmistha Mukhopadhyay [00:01:13] Thank you. It's my pleasure.

Ryan Howell [00:01:15] So, our listeners always like to hear where you've come from and what your background is, so tell us a little bit about where you grew up and talk to us about that journey of getting towards nuclear.

Sharmistha Mukhopadhyay [00:01:24] Okay. So, I grew up in India in a city called Calcutta. Now, it's called Kolkata. That's where the British had their capital.

Ryan Howell [00:01:32] That's the north of India, right?

Sharmistha Mukhopadhyay [00:01:33] It's east of India. It's east of India. It's east of India, you know that's where the East India Company was made with the British, and so that's the history of the place. I grew up there, I did my master's from Calcutta and then I moved to US due to family reasons. My husband moved and somehow I came to the University of Kentucky when my husband was doing a post-doc.

Sharmistha Mukhopadhyay [00:01:57] And in between, after my master's and before I came to the US, I was teaching high school in India, which is one of the most exciting jobs I've had, although I'm talking about 25 years back because teaching physics in high school in India is a big challenge. That's where you solve most of the problems and teaching those to 17-year-old kids was not a very easy job. To make the problems look simpler and to get it across to them, that was a big challenge I felt.

Sharmistha Mukhopadhyay [00:02:29] So after that, I came to Kentucky and I wanted to be a schoolteacher, a high school teacher. But then I realized in the US, to become a high school teacher is a challenge. You have to get a lot of certifications, there's that, and I didn't have the patience for that. Rather, everybody at the university was telling me, "Why don't you join the Ph.D. degree?" which I didn't want, because I always felt that was more difficult and it's time consuming. But that was the easier thing to do, so I just went into that.

Sharmistha Mukhopadhyay [00:03:02] I started my Ph.D. My daughter was a one-year-old, so I started doing my Ph.D. with her. And and it looked easy because, of course, it was the course work and everything went on pretty smoothly. It was more or less repetition of what I did in my master's. Then I saw almost everybody's struggling because of the lot of mathematics that you need, which I already had, so that made my life easy.

Sharmistha Mukhopadhyay [00:03:27] And then, I had to choose my project, my Ph.D. project. I didn't have many options. Sad to hear, but I'm talking about 2005, quite sometime back, and most of the faculty refused to take me because I already had a child. So without an option, I spoke with my supervisor, Dr. Steve Yates, at Kentucky, and he was happy to accept me in the nuclear field. And we had an accelerator, the University of Kentucky Accelerator Laboratory. We have a Van de Graaff generator. We do most of the experiments there, the measurements there, but most of the experiments are long run. 24 hours for 30 days we run, but we have shifts. It's a challenging thing, but he was happy to include me in the group, and that is how I started my journey into nuclear physics.

Sharmistha Mukhopadhyay [00:04:24] I was mainly doing inelastic neutron scattering and looking into gamma rays and studying the structure of the nucleus, which is very different than what type of work I do here. But after that, I moved to the industry. And so after completing my Ph.D. for four and a half years... Because I was lucky that all of my projects were on campus, so I didn't have to wait for any beam time or running around. And some of the projects were challenging, but we got to understand the physics, what we wanted to know, for the time being. But then physics changed later. But so, then I moved to industry.

Ryan Howell [00:05:02] Right. And that's what landed you at Sun Nuclear?

Sharmistha Mukhopadhyay [00:05:04] No, that's what landed me in Boston. So from 2008 to 2011, I was in the scintillator company called Radiation Monitoring Devices.

Ryan Howell [00:05:13] And what was your role there?

Sharmistha Mukhopadhyay [00:05:14] I was, of course, a scientist. That was one of the very exciting things I was doing. Right now, it's a big... You have the detector off the shelf, but that was the time I was developing the prototype neutron-gamma scintillator, which nobody had heard of before. And that's now in the ElpasoLight scintillators, which are very much now in the market. CLLB, cesium, lithium, lanthanum bromide; cesium, lithium, lanthanum chloride, and huge families. But I was the first one, almost the first one, to test and make detectors out of one millimeter scintillator, which now has grown to one inch or even two inches. So, I was among the first few to work with those prototype scintillators.

Sharmistha Mukhopadhyay [00:05:58] And that was the first scintillator which did that neutron-gamma discrimination, plus we had the thermal neutron gamma equivalent in energy peak around three MeV, which made a marvelous detector to detect thermal neutrons, even if you didn't want to do an n-gamma, pulse shape discrimination and all those complicated things. So, you can make it work simple and you can also get it to work in a more realistic way. So, that was my one of the projects apart from other garnets and scintillators that I worked on.

Ryan Howell [00:06:34] Very good. And what changes when you go from one millimeter out to an inch?

Sharmistha Mukhopadhyay [00:06:38] Oh, my God, it's huge. Of course, I was doing the detection part, and I was not the real person to do the scintillator. With all the challenge, I'm sure they must have had sleepless nights. It's basically the light collection.

Ryan Howell [00:06:51] So it makes it more sensitive?

Sharmistha Mukhopadhyay [00:06:52] As you grow, it's very difficult. Your lights get trapped within the scintillator. All you want from the scintillator is a big light output. That's the thing, because as light output goes, noise increases. You don't get to see what you want to see. And that's a big challenge so that the light reflects out in one surface and doesn't get lost from that. So, that's one of the biggest challenges.

Sharmistha Mukhopadhyay [00:07:14] So the way we used to do it is when I would do the testing and the measurement, we would talk with the detector developer and they would see what's happening and then they'll go back, grow another scintillator and come back. And this is how we would talk. And of course, the recipes are secret.

Ryan Howell [00:07:30] Sure, sure. But that's the process.

Sharmistha Mukhopadhyay [00:07:32] That's the process.

Ryan Howell [00:07:33] So maybe for our listeners who don't know what a scintillator is, can you talk a little bit about what that exact technology is and how that works?

Sharmistha Mukhopadhyay [00:07:39] Yeah, that's very simple. It's simple. A scintillator, something scintillates, gives out light. If there is an interaction, whatever may be the interaction... For us, the interaction is all the ionizing radiation that we were looking into, mainly the neutrons and the Gammas, those are the radiation. The scintillator was mainly to detect those radiation, but there are scintillators for other radiation. So when this radiation is incident on the sample... We call it a scintillator.

Ryan Howell [00:08:12] The material.

Sharmistha Mukhopadhyay [00:08:12] Yeah, the material. Some chemistry happens; it's complicated. There is some jumping of electrons here and there which gives out some light. And the amount of light we get is directly proportional to the energy of the incident radiation that was falling onto the simulator.

Ryan Howell [00:08:33] And that's what the electronics can then interpret as the spectrum of the radiation.

Sharmistha Mukhopadhyay [00:08:38] Of the radiation, yes. But then again, there are other things happening, but this is just a simple way to explain what the scintillator is. And so, the main objective is to get as much light as you want to collect out of the scintillator, but again, that is not the end. That light has to fall into some of the electronics, which is usually a photo multiplier to another solid state electronic tube, called a solid state photo multiplier tube, to get the electrons out and then try to extrapolate what we got and what was incidental on the main detector. So, that's how a scintillator works in a nutshell.

Ryan Howell [00:09:23] That's great. So that was your work up in Massachusetts. How did you end up in Florida?

Sharmistha Mukhopadhyay [00:09:28] Oh, no. Then in between there was a long story. I'm moving around all over the world. Okay, so after that, I had some family things, so I moved back to India. There, I was a professor and I was the head of the department of an engineering college. And I was basically designing courses, teaching students and administrating. I was in charge of about 40 faculties who were working under me, and there were 500 students. I knew 50% of the students by name because I used to interact quite a lot with them to understand their background and things.

Sharmistha Mukhopadhyay [00:10:03] So that was four years, and then I realized, within a couple of years, within the four years that I'm going away from research every day. And I couldn't get any interesting projects out there, and that made me come back to the US, back to Kentucky. And then, I was working with some interesting... A neutronless beta decay project, more physics oriented. And luckily, good work happened and then I moved to Florida. So, it's a long...

Ryan Howell [00:10:37] Roundabout. Well, it's good that you're back in the States. You worked for Sun Nuclear for a little while.

Sharmistha Mukhopadhyay [00:10:41] Yes.

Ryan Howell [00:10:42] And that was still in the detector side?

Sharmistha Mukhopadhyay [00:10:45] Sun Nuclear is a medical physics company. Now, Mirion has bought it, after I left. And so, they have these different detectors to basically analyze the beam from the clinic. Back then, it was mainly clinic, but the instrument that was there to detect... So, my project was mainly to see how much radiation damage it's getting from the measurement. So, it was not directly building up a detector, but again, working on some type of instrument which has radiation falling on it and seeing the...

Ryan Howell [00:11:26] That's radiation monitoring, right?

Sharmistha Mukhopadhyay [00:11:27] More like radiation monitoring, yes.

Ryan Howell [00:11:29] Can you talk a little bit about the role of radiation monitoring in these advanced nuclear technologies?

Sharmistha Mukhopadhyay [00:11:37] Those detectors, especially the water phantom or the other detectors, that is mainly for detecting the photons and the X-rays and other reaction channels that opens in high energy. There are some motors and electronics which are driving things around. Some of the theoretical work and experiments were to find out how much dose those areas were getting, and which will not damage. So that once we make an instrument and we put it out in the market, it should be there for 15 years or 20 years without any radiation damage.

Ryan Howell [00:12:19] Okay, so you were working on the service life of the detector.

Sharmistha Mukhopadhyay [00:12:22] Yes, more on the service life of the detector, which is very different.

Ryan Howell [00:12:25] So radiation damage to materials. Had you had much background in materials before?

Sharmistha Mukhopadhyay [00:12:29] No, no. But it's a big collaboration, right? Like, it's not me, so there was another person who would run a lot of simulation, and then I would go to the lab and do the measurement of how much radiation we are getting, and then extrapolate to some other... We would not do all the experiment, but just to see what we were getting and what we do expect to get from a year out, or 10 years or 20 years down the line. So, that's different.

Ryan Howell [00:13:01] No, that's great. So, how did you land here at Georgia Tech? Was there anything in between Sun Nuclear and here?

Sharmistha Mukhopadhyay [00:13:07] No, no, no. Georgia Tech, this is very fine. This is almost like my dream job, because if you look into my history, I like industry. And R&D in industry, I really like. It's very upbeat and you get to see things which nobody has seen before, and you're working on that before it comes out to the market, and it's your child.

Ryan Howell [00:13:33] Right. And you also seem to have a passion for students.

Sharmistha Mukhopadhyay [00:13:35] I have a passion for students. I think more for R&D. I definitely like to develop something. I am the one who is seeing or my team is the one who is seeing. So, that's true. And not too much doing the academic job. I like teaching, but not so much bookkeeping, which is now... So, that's the thing. But then, I felt this job was almost a balance between... Like, I have an academic environment around me, with hopefully, some industrial overlap. And for my industrial background, I can always bring things here, so that's always open. And of course, my favorite neutrons are here too, so I can work with them. I work with neutrons and with different projects.

Sharmistha Mukhopadhyay [00:14:22] I work with some of the academic projects, which are again, in industry. That's missing, because in industry, they have a goal and they are focused on that. Academics, you have variety of projects. And also, those are pretty much the first time. Although the real R&D, the real research and development, again, starts from years. So, that was the reason I felt that this job is pretty much a balance. And I can teach if I want to a little bit and interact with students, because young minds keep you always ready.

Ryan Howell [00:14:56] That's great. Yeah, industry definitely takes your broad and makes you very focused and narrow and you get to come the other way where you've got industry experience and get to expand that to all the students.

Sharmistha Mukhopadhyay [00:15:06] Yes.

Ryan Howell [00:15:07] That's fantastic.

Sharmistha Mukhopadhyay [00:15:09] And I also have students... because I've seen the other side a little bit more than...

Ryan Howell [00:15:15] You can talk from the real world side.

Sharmistha Mukhopadhyay [00:15:17] Yes, real world. But fortunately, the industries where I've worked and the people I have worked with, they have given me a lot of freedom to do a lot more research than just, "Okay, just do this." So, I had a little bit of freedom to go a little bit out of the way and explore some other things, even if it was not focused just on the proposal.

Ryan Howell [00:15:36] Yeah, that's great. So, talk to us about your fascination with neutrons and what you like to do with them here.

Sharmistha Mukhopadhyay [00:15:43] Okay, so the neutrons... The interaction of neutrons is very interesting because unlike other radiation, of course, photons are also charged and as neutrons, they do not have charge. But the way they interact with the material doesn't only depend on the density. Of course, it doesn't depend on a different type of scattering or, finally, the inelastic of... Some of the material, the way it interacts is different. And then, thermal interacts and fast neutrons, so there's a whole range of things.

Sharmistha Mukhopadhyay [00:16:20] Really, I'm fascinated with detection, like how to detect neutrons. And that's what I've done on some of the development, but those are mainly for thermal neutrons. But at Georgia Tech you have the enormous number of instruments to do not only the thermal neutrons, but also the other neutrons, thermal and the fast neutrons. And we have different neutron generators, we have neutron sources. Pick up a range, that neutron is available, which is absolutely fascinating.

Sharmistha Mukhopadhyay [00:16:50] So, most of my work goes in doing the instrumentation part, because some of these detectors are very old. You won't believe it, when we call these people to say that we need a servicing, they do not believe that they had made those instruments. They're like 30 years old, but they work fabulously because the neutron characters have not changed.

Ryan Howell [00:17:15] That company didn't, but the company that they bought, that they bought did.

Sharmistha Mukhopadhyay [00:17:18] Exactly, exactly.

Ryan Howell [00:17:20] I've been there before buying parts off of eBay to try and keep stuff going.

Sharmistha Mukhopadhyay [00:17:23] Yes. And even the label... On the label they have the phone number and you will see that there have already been three changes since the time they have sold you that detector. The interesting part here is there are many detectors and most of the time, my work goes in getting the field characterized. The neutron source for those it's getting at what distance and what dose we would have gotten if human tissue was there and how can we mimic some of the situation.

Sharmistha Mukhopadhyay [00:17:59] Like, for example, when you're going to space, there's a lot of radiation around. Now, do we go up and do all the measurements there? That's not possible. So we do some simulations. And then with our sources, we try to reproduce that type of an environment to get a similar dose rate, and then we bring our detectors and other instruments just to check whether we are getting it and then expose our interest in the material we are interested in to see the effect of dose. That's something which I have not, again, worked in before. So, to characterize the neutron field, which is I think very, very fascinating.

Ryan Howell [00:18:40] Are there any long-going studies that you guys have partnerships with that you can talk about?

Sharmistha Mukhopadhyay [00:18:43] So, we have this facility called the Radiological Science and Engineering Lab at Georgia Tech.

Ryan Howell [00:18:56] Which you're the manager for.

Sharmistha Mukhopadhyay [00:18:56] Which I'm the manager for. That's basically... You cannot keep sources right everywhere. So, this is mostly the place where all the sources are kept or we have access to all the sources. And this is where I work with different people all around Georgia, like other departments as Georgia Tech who are developing different detectors. We have projects with Emory with trying to understand the effect of these radiations on DNA. So, that's an ongoing project, and I'm sure that will be a pretty long project. And we are going step by step to understand what's the effect of this radiation.

Sharmistha Mukhopadhyay [00:19:39] First, we understand what the radiation is, we try to characterize the field, and then we make it incident to some of the cells. We have done Phase Zero work and the results are out. But we have some other ideas in mind. And we are working, mainly, with Emory for this cell project. And there are the different projects. Most of my projects are overlapping in testing new scintillators and new detectors that students are developing to see the response.

Ryan Howell [00:20:11] So, is this like marrying the sciences and the humanities together?

Sharmistha Mukhopadhyay [00:20:15] Yeah. Yes, all these things, we have to bring all together, right? Because the biology, I think that was always the thing that they didn't have access to this type of radiation and the sources. And now with the medical physics system, like with the clinic and the flash theory and things coming up, high radiation things, now these are getting more marched together. And we have the capability to produce those fields somewhere here at Georgia Tech, so we are trying to mimic those in the radiation environment and see what the experimental results come out to be.

Ryan Howell [00:20:49] Yeah, that's great.

Sharmistha Mukhopadhyay [00:20:50] Apart from in the simulation, which is there already.

Ryan Howell [00:20:53] Yes, yes. So what new projects or future projects are you going to be working on soon that you're excited about.

Sharmistha Mukhopadhyay [00:21:02] Future projects, of course, the moment we get a new instrument... One of the projects, there's a new detector out there called ADVACAM Pix. It's a hybrid semi-conductor detector, and we should be getting one field module very soon just to check it out. I'm excited about that instrument because that can do a lot of those measurements, linear energy transfer, and all the things that we are doing with different detectors. First, to understand how the detector works and to check all our measurements that we have done, and then to go from there and beyond, like bringing them into the class laboratories. I'm really interested to get these new detectors which are there in the market, to bring it into the lab course. Already, we have some fascinating new digitizers and everything in the lab modules, but incorporate them into the curriculum.

Ryan Howell [00:22:00] Yeah, so as we bring all these detector technologies into the 21st century where we're going all digital, we're going from these analog things where it was a lot of hardware that is actually physically changing dials and knobs and you can see things on the scale, and now we're going to digital. Have you seen any pushback from the industry or from the radiation protection side on trusting those technologies that are now just codes and software analyzing these?

Sharmistha Mukhopadhyay [00:22:26] I have not worked exactly on that part, but I personally do a double-check no matter. Because the good thing about digitizers... They are fascinating and lab class is excellent, but sometimes when we are doing some detailed work... Just to understand, because the digitizers are programmed by someone and they have the limitations which we do not know. Only the company knows. I knew the detectors I developed because I had also done those things, but then when we go and sell it, we do not tell all the things. You know, there's no point in telling that information. So whatever we do, we definitely take a signal and put it to the oscilloscope. Maybe I do it because I'm from the old school. And I don't know how long people will continue to do that.

Ryan Howell [00:23:14] You have to pass that along, yes.

Sharmistha Mukhopadhyay [00:23:15] Yes, and of course, every digitizer does have its waveform that you can see, which I really do not know how they do it. There is some signal processing they do even before you get to see, though, the waveform on the digitizer. So, the first step is still the analog part and looking into the scope trays, and if you are happy then I do the rest of the processing. And sometimes we do a comparison and do it with some analog electronics. With the new modules, I just try to get to... Because I'm used to it. And then go move to digital using digitizers. Let's see, when we get these new instruments, how do the results match with all the old detectors and systems we have. So, that's something probably...

Ryan Howell [00:24:03] Yeah, that's very interesting. And so, as the nuclear industry seems to be booming right now, and we're talking about thousands of new reactor types and thousands of different plants coming on line, how do you see these instruments and detectors marrying in with that and being baked into the solution?

Sharmistha Mukhopadhyay [00:24:22] In a good way, these are small detectors so it's easy to keep them anywhere, but we have to check how much radiation damage will be done. But I think it's very portable and convenient. You can take all the data outside so you can always constantly monitor compared to, probably, the old ones that were there. They were bulky and you had to always have those long cables and all the data doesn't get recorded. But I think with this, it will definitely help to monitor the doses for places where maybe it was not easy to access. Because these are very small; it's a 1.5 centimeter by 1.5 centimeter, that's the sensor. So it's easy, but we have to check how much in a wave will go to the saturation, and that's where we're looking forward to test these instruments.

Ryan Howell [00:25:20] It sounds like you guys are getting a new reactor here. Will you get to play a part in taking measurements over there?

Sharmistha Mukhopadhyay [00:25:28] Well, when we've got all the instruments, anything I get a green signal for, I'll be happy to go and start them in our work. And that's why it's good to do something with characterization, with systems we already know. And then, of course, an unknown, it's easy to...

Ryan Howell [00:25:43] Yeah, then you have something to compare it to in baseline.

Sharmistha Mukhopadhyay [00:25:45] Yes, compare it to the baseline. And we are confident of what we have here, and the students are working hard on those projects.

Ryan Howell [00:25:52] Very good. Well yeah, is there anything that we've missed that you'd like to talk about? Any projects that you're particularly fond of along your career path?

Sharmistha Mukhopadhyay [00:26:03] Of course, the most interesting project was the scintillator that was developed at Radiation Monitoring Devices. Of course, it's on the shelf now, but getting a scintillator that gives a very good gamma spectra. It also measures the neutron and gives a thermal neutron peak around three MeV, which is far away from the rest of them, most of the gamma backgrounds that we see. Getting to make the thing work into a detector system with different types of charge integration and other things to make this detector work, that was very, very fascinating. And to understand how better we can get rejection ratio resolution and make it user friendly to the customers. So, that was good, yeah.

Ryan Howell [00:27:02] And that was on the radiation protection side and working with health physicists, right? Do you see that being the future for technology, just continue the push there?

Sharmistha Mukhopadhyay [00:27:14] Yes, of course. Because we need a smaller system and a more flexible system; that's important. And like for example, the detector of that, we can fix that in the market; one device capable of doing many things. So, that's important because it's not only one radiation, right? All the radiations around. So, understanding the dose from everything, that is a good step forward. Yes, absolutely.

Ryan Howell [00:27:43] Well, we always like to end our podcasts with something hopeful for the future. So can you talk a little bit about where you hope things go here within the Department at Georgia Tech or within the nuclear community abroad?

Sharmistha Mukhopadhyay [00:27:58] Finally the nuclear community, of course, has woken up, which is a good thing. Nuclear power almost got a little bit pushed under the carpet, so people are aware that this is a solution. And I'm sure that in the nuclear community, always felt that this was the right solution, but now we have the support from the rest of the world and the rest of the people here. So that give you a double advantage of speaking out loud. And this is where we are going, and this should be the right direction. Use less electricity, understand where we need and how we can solve, and that's where the nuclear power plant will help us to reach.

Sharmistha Mukhopadhyay [00:28:39] And everyone is working for the best way to get it in a safe way so that it reaches to the people without taxing them for the money. And making them safe; the people who are working them, they are not getting radiation. So, we are thinking about every aspect. It's not that, "Okay, there's a nuclear power plant. We get a lot of energy and that's all." There are different aspects that we all are working on to make our life better and the next generation's life better.

Ryan Howell [00:29:11] Very good. Well, Dr. Sharmistha, it's been a pleasure speaking with you. Thank you so much for your time.

Sharmistha Mukhopadhyay [00:29:17] Thank you. Thanks for having me.