Department of Physics

PhD student’s research solves 30 year nuclear physics challenge

Researchers in Surrey’s Nuclear Physics Group have studied a critical astrophysical process that happens when stars explode, using a unique facility at partner TRIUMF in Vancouver.

Photo: David Hardy

The research, which was led by PhD student Ryan Wilkinson with Dr Gavin Lotay and Professor Wilton Catford within the Department of Physics, has been published in Physical Review Letters in December. It was conducted in partnership with the TRIUMF National Laboratory in Vancouver, Canada.

The Surrey team worked at TRIUMF, using its DRAGON (Detector of Recoils and Gammas Of Nuclear reactions) facility, to replicate a specific nuclear reaction (transforming neon (specifically19Ne) into sodium (20Na)) which happens in exploding stars. The analysis reveals the speed at which the reaction takes place, and is significant because it tells us more about these astronomical events which are responsible for the formation of most of the light chemical elements we find on earth and observe in our Galaxy.

This particular reaction – which physicists have been investigating for over 20 years – is notoriously difficult to study because it involves using a beam of the rare and unstable nucleus 19Ne, and requires the conditions that occur in an exploding star to be recreated in a terrestrial laboratory. Only two other similar direct measurements of the reaction have ever previously been attempted, both of which were unsuccessful.

Ryan Wilkinson said: “The breakthrough we’ve achieved has been made possible through our in-depth knowledge of the relevant nuclear processes, a critical evaluation of existing literature, and our use of the DRAGON spectrometer which enabled us to design a direct measurement that would tell us the rate of reaction immediately. The result we have finally brings together over 20 years of evidence and solves a nearly 30 year issue.”

Dr Lotay commented: “It’s a very exciting study and an incredible feat for a Surrey PhD student to have a first named author paper in a publication as prestigious as Physical Review Letters prior to the submission of their thesis.”

The paper, ‘Direct measurement of the key Ec.m. = 456 keV resonance in the astrophysical 19Ne(p,γ)20Na reaction and its relevance for explosive binary systems’ was published by Physical Review Letters on Monday 11 December 2017.

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