“We’re all made up of star stuff” – a mantra most scientists and researchers use when describing TRIUMF’s DRAGON – Detector of Recoils and Gammas of Nuclear Reactions experiment. Recently, we had the chance to sit down with Thanassis Psaltis, a Physics PhD Candidate at McMaster University. His research interests lies in the area of experimental nuclear physics, which is how he ended up working on TRIUMF’s beloved DRAGON experiment! Thanassis was able to give us some insight into the world of Nuclear Astrophysics along with explaining how “DRAGON is like a prism for charged particles.”

Tell us about yourself!

I am currently pursuing my Ph.D. in the Faculty of Physics and Astronomy at McMaster University under Professor Alan Chen. I was raised in Greece and completed my undergraduate studies at the University of Athens. As a person, I’ve been curious my whole life. I like to answer the big questions and I think the origin of the elements is one of the biggest ones. I was split between nuclear physics and astrophysics, but luckily I discovered a relatively new branch of physics that combines the two, Nuclear Astrophysics.

What led you to TRIUMF?

My supervisor, Dr. Alan Chen is a core member of DRAGON. He was a postdoctoral researcher when DRAGON first came to life. He was collaborating with a group at TRIUMF and he had this idea for the experiment, which correlates with my thesis. He asked me if I was willing to come aboard and I was like “sure, why not!” It was hard work, much more than what I had expected but it’s definitely worth it.

What was your first impression of TRIUMF?

My first impression was “this place is amazing!” I fell in love with the lab instantly because it’s just so perfect. The people are remarkable and overall TRIUMF is not only an astounding place to conduct research, but also a great place to grow and develop as a person and a researcher.

Can you tell us about your work with DRAGON - the TRIUMF Detector of Recoils and Gammas of Nuclear reactions?

In nuclear astrophysics, one of our primary goals is to uncover the origin of the elements in the universe. Fundamentally how the different elements that make up everything made out of matter were created. What we want to accomplish in nuclear astrophysics is recreating the reactions that happens in stellar environments. By doing this we can actually tweak the models we have in order to recreate the abundances we observe in the solar system. This is the main goal. We find that there’s actually quite a bit of curiosity and interest in the creation of heavy elements. When we say heavy nuclear physics we mean heavier than iron, and iron is the most stable element. Heavy elements are mostly created in explosive environments, for example in supernovas and x-ray bursts. We’re not 100% sure of how these elements are created but there are several different processes that can create these origins. There is a very small group of elements, about 35 isotopes that can either be created by the 2 main processes that we know of. This is called the b-nuclei, and we’re trying to understand how these b-nuclei are created in the universe. Right now we think they are created in the supernova explosions. 10 years ago a new theory came out, that suggested that the mission of neutrinos after the supernova explosion could actually affect this nucleosynthesis. For this reason, it is called the nu-p process and the nu stands for neutrinos. So I’m studying one reaction right before this nu-p process starts. I believe by changing some of the nuclear properties of that reaction we can eventually change the whole nu-p process, nucleosynthesis and eventually change the imbalances we observe for certain heavy elements. My project is with DRAGON but I take up experiments on other labs and here at TRIUMF as well (ex: TUDA & TIGRESS). 

Will DRAGON assist in advancing the field of Nuclear Astrophysics?

The nu-p process is a new theory; therefore every experimental input for this model is critical. In terms of nuclear experiments, any experimentation using radioactive beams is important. This was actually the 9th time DRAGON ran a radioactive beam experiment and beyond the whole nuclear astrophysics aspect of the project, there are a lot of technical details about DRAGON. By doing this experiment we really pushed DRAGON to its limits and it seemed that it could hold that. DRAGON studies reactions in inverse schematics, meaning we usually have a low mass beam, for example a proton or an alpha particle that hits a stable gas target. If we use a preservation momentum while doing this, the nuclei that they’ve created, the recoils as we call them, have a small angle compared to the beam. One needs to note that DRAGON and all the recoil separators out there have a maximum acceptance angle. We run some simulations before hand to see if it can be executed in reality and it actually does work, which we’re very glad about!

Do you have an analogy for DRAGON?

DRAGON is a recoil separator, meaning it separates reaction particles like the ones we create in the reaction and the ones that come from the beam. I’d say it’s very similar to a prism. Let me elaborate. As light hits a prism, it separates according to the colour right? This is actually the wavelength. Like this, the same thing happens with charged particles, almost similar to the beams we use. There are two things we can do here: we can use electrostatic dipoles to separate them according to their mass and magnetic dipoles to divide them according to their charge. DRAGON is the best recoil separator out there because it can suppress a great deal between the beam and the recoils. For example, if you have 1 billion particles and just one of them is the recoil, it can someway separate, consequently getting us the one we need. To summarize, DRAGON is like a prism for charged particles.

What do you want to personally achieve with this experiment?

TP: Ph.D. projects are imperative for any researcher. You take a project, take a problem and attempt to solve that. I see my Ph.D. project as very colossal, as it not only involves reactions but simulations as well. This endeavor of mine will enable me to do anything after I’m finished with it (not anything though – I won’t travel into time or fly!).

What have been some of your highlights at TRIUMF?

TP: Working at one of the best, productive, eye-opening facilities in the world gives you many opportunities to not only meet with outstanding researchers but to also discuss your research with them. TRIUMF has an excellent environment and enables both students and researchers to succeed in their work. In the summer of 2017, I resided in Vancouver for three and a half months to study DRAGON and work with postdoctoral candidates at TRIUMF. This helped me in becoming very comfortable with running experiments. With being able to travel to TRIUMF, I’ve also been introduced to the breath-taking city of Vancouver! There’s just something about this place that gets you falling in love with the city.

What do you like to do when you’re not conducting research?

I love travelling and sometimes travelling goes with my research so that’s pretty neat! I enjoy running as well; I actually used to be a track and field athlete in high school and in college I used to compete in 10k races and marathons!

Thanassis is also a resident within “The Bridge” web residency program, which matches an artist and a scientist for 4 months. Thanassis is collaborating with artist Matej Vakula, a multimedia artist who fashions simulations of astrophysics environments. Matej is the artist in residence at the Center for Molecular Imaging and Nanotechnology at the Sloan-Kettering Cancer Research Center and is currently completing his PhD in Bio & Procedural Art in New York. Thanassis and Matej hold a weekly blog where they discuss the progress of their work. Their goal is to create a short sci-fi film, which will be screened at McMaster’s W.J. McCallion planetarium in which Thanassis also works at. Their film “The Dragon Theorem” will include TRIUMF’s DRAGON experiment! Best of luck on all your future endeavors Thanassis and Matej, we’re excited for this upcoming film!

-Ashwini Canagaratnam, Communications Assistant