First CHIPP postdoc prize goes to PSI postdoc

The CHIPP PhD prizes, awarded every year since 2008 during the CHIPP Annual Meeting, have become a bit of an institution; however, this year’s meeting had a new prize in store: the CHIPP postdoc prize. Its first recipient is PSI postdoc and Marie Curie COFUND fellow Efrain Patrick Segarra, who received it for “his outstanding contributions to the n2EDM experiment at PSI, including its first Ramsey and EDM test measurements, major improvements in magnetic field uniformity and polarization control, and culminating in a novel method to extract the ultracold neutron spectrum and storage properties.”

Currently a postdoc at ETH Zurich and still on the n2EDM experiment, Segarra has a history of making a big impact in very specialised experiments – previously a proton-structure experiment at Jefferson Lab in the US, now at the PSI’s n2EDM experiment, which looks at whether the neutron has a tiny electric dipole moment (which would be a scientific revolution, not only because it would prove our current understanding of particle physics needs modification but also because it would give a clue to why matter dominates over antimatter in the universe.

Segarra hadn’t always wanted to be a physicist; in fact, he started out studying computer science and engineering at the University of Michigan. By a fluke of fate, he took a basic physics class and discovered he really liked the topic. His lecturer played a major role in changing his course of career: “He took me aside and talked to me about all the exciting stuff happening in modern physics today – quantum communication, the Large Hadron Collider, electron-positron colliders… and I thought “Wow, this is so cool!”,” Segarra says. He changed his life plans, graduated in physics and did his PhD at the Massachusetts Institute of Technology MIT.

He chose a PhD project that let him experience all stages of an experiment, from design, construction and calibration to data analysis to study the internal structure of protons and neutrons bound inside nuclei. “It was very important to me that my work would make an impact,” he recalls. “It turned out that I really liked research and in the end I got to build and run my own 0.5-million-dollar detector!” His MIT supervisor was just as motivating and passionate as the physics professor at the University of Michigan. The results of this experiment are still under final review, but due to be published soon.

For the postdoc that traditionally follows a PhD when you’re on track for a career in academia he looked for other smaller experiments where he could make an impact. He launched his search in Switzerland, as his wife had just accepted a position in Zurich. And while he did find a small experiment – n2EDM has about 60 collaboration members and is housed in a magnetically shielded cube some 5x5 metres big –, he changed scope completely. “Before, I looked for new physics manifested in big effects, where small corrections didn't matter,” he recalls. “Now, I am on the lookout for an extremely tiny property – the neutron electric dipole moment. That is really super high-precision physics – but it’s really a different side to the same coin.” After all, both explore fundamental properties of neutrons and nuclei.

Having got his head around n2EDM physics including quantum mechanics and properties like spin, he set out to leave his mark on the experiment. The conditions under which n2EDM needs to operate are highly complex. It needs years of commissioning – the experiment’s extraordinary sensitivity means that its systems like the ultra-precise magnetic shielding, high-voltage control and magnetometers need to be tested and fine-tuned meticulously to make sure even the smallest effects are not mistaken for real signals – and will take data for about 200 days. “When we turned on the experiment, we saw that the numbers of neutrons that we could store coming from the ultracold source were different from what we expected,” Segarra explains. “Some disappeared and we wondered where they went. It was likely connected to their energy, so we developed a technique that lets us extract the neutrons’ energy spectrum without disturbing them. Then we used that extracted spectrum and saw it didn't match our design goal. So the collaboration suggested to modify the storage material of our experiment to greatly increase the number of neutrons we can store – which greatly improves our sensitivity.”

Still on n2EDM and continuing his work, he has now changed affiliation to ETH for his second postdoc that also includes lecturing and tutoring duties. As he really enjoys teaching and working with students, this is just the right combination for him. And the fact that he gets to teach Physics 1 – the course that got him here – is an added bonus. “My professors made a huge impact on my life and I want to do the same for my students. I hope I can motivate them in just the same way.” And there is another life-changing event in store for him soon: he will become a father in the coming weeks. Congratulations and all the best!

Barbara Warmbein