Last winter, nine of us decided to enter Beamline for Schools, a CERN (European Organization for Nuclear Research) competition where high school teams design real particle physics experiments. Upon being selected, students would receive the once-in-a-lifetime opportunity to perform their experiment at CERN. This competition draws proposals from hundreds of teams from dozens of countries, making the standard for the proposals very high.

How we got started

I first came across Beamline for Schools two years earlier, when I was exploring opportunities in physics beyond the classroom. I went on to participate in the competition that year, developing a sense for how demanding the process of developing an experimental proposal is. This prior exposure made it easier for me to help our group get started. 

Early meetings were a lot of reading. The group – which consisted of juniors Tanay Mangal, Ishan Kasam, Mohammad Golji, Jasmine Palit, Rishi Gandhi, Chris Xu, Nichelle Thinagar, Arnav Prabhudesai, and myself – started by going through background material provided by the BL4S website. This involved learning about example experiments, the beams and detectors provided at the site, and reading through several winning proposals. Each of us then independently researched a potential experiment topic and pitched it to the group.

We had proposals ranging across various different areas of physics. We ultimately agreed that one idea stood out the most. One of our members noticed that a specific assumption embedded in every radiation transport code used by NASA and ESA had never actually been tested with a real particle beam. 

The science

Mission planners protecting astronauts from dangerous cosmic rays have two tools at their disposal: passive material shielding (dense plastic or aluminum panels that absorb radiation) and/or active magnetic shielding (deflection of charged particles). The standard formula combines both by treating them independently. That is, the combined protection is simply the product of each individually. For example, if passive material shielding lets in 50% of cosmic rays but active magnetic shielding lets in only 10%, then a setup which combines them would let in 5%. 

But there is a geometric reason to doubt this assumption. When a magnetic field deflects a proton, the particle enters the shielding material at an angle. The angled path is a longer path, meaning more radiation gets absorbed than the formula predicts. Our GEANT4 simulations suggest the real deviation could be 2-4% – small, but real, and potentially enough to skew astronaut dose estimates for long missions. 

Our proposed experiment uses CERN’s T9 beamline to fire protons at energies matching the galactic cosmic ray spectrum through three configurations: material only, magnet only, and both together. Comparing those measurements tells us whether the standard formula holds.

Talking to the experts

Though it was in no way a required component of the application, once we had a draft, we reached out to researchers. This was to solidify the physics behind our proposal which we might have messed up. Ian Chandra, a materials scientist at SpaceX, confirmed that the multiplicative assumption we were targeting is unverified experimentally. She pushed us to frame the experiment as one capable of disproving it, not just validating it.

Professor Stephane Willocq, an experimental particle physicist at University of Massachusetts at Amherst with experience on the ATLAS and CMS detectors at CERN, reviewed an early version and gave us specific feedback on material choice. Professor Aravind Padmanabhan at WPI validated our physical motivation. Getting feedback from researchers had a major impact on how we shaped our proposal. One of the biggest changes came in how we framed our objective. We initially focused on validating an unverified multiplicative assumption, but after discussions with experts, we shifted toward a broader approach. That is, one that not only tested the assumption but also acknowledged the possibility of disproving it.

What we’re hoping for

A positive result would mean the transport codes used to plan crewed missions need revision. Even a negative result sets the first quantitative bound on the assumption, which is itself a contribution. 

Selection results come out later this year. Whether or not we make it to Geneva, spending a semester doing particle physics research and writing a rigorous proposal was quite the experience and we all learned a lot from it. 

For more information on BL4S, check out https://beamlineforschools.cern/