Two weeks ago, the Collinear Resonant Ionization Spectroscopy (CRIS) experiment at ISOLDE performed some of the world’s most sensitive measurements of the nuclear structure of francium, one of the rarest and least-understood elements. Gathered in record time and with excellent background resolution, the results are in good agreement with model predictions. The developer of their model? 2012 Summer Student, Ruben de Groote.
When de Groote arrived at CERN this June, he joined one of CERN’s smallest experiments: CRIS. With a team of just 8 people at CERN, the CRIS experiment has become the world’s best facility to study the nuclear structure of light francium isotopes. By using a combination of resonant ionization spectroscopy and collinear laser spectroscopy, the experiment can select francium beams in a specific nuclear state with little background noise.
As part of his thesis, de Groote has been developing a model – based on work by his University of Leuven colleagues – that looks at the saturation of the ionization process in francium isotopes. “While the model has applications outside CRIS, collaborating with this experiment gave me the opportunity to work with the equipment that my theoretical model describes,” says de Groote.
In August, CRIS carried out its first successful run using laser beams from ISOLDE’s RILIS facility. Beams were only available overnight – and only for 4 days – but it was enough time for the team to gather data on 5 different francium isotopes. “We can already see a very good agreement between Ruben’s model and the results,” says project leader Kieran Flanagan, of the University of Manchester. “This will probably be a paper in its own right and follows up on work carried out by another (former) summer student, Lucas Peeters, who is now starting his PhD.”
“Finding out that the model I'd been developing shows promise has, of course, been amazing,” says de Groote. “The realization that the work you've been doing in the past months actually helps an experiment and allows the other physicists in the collaboration to focus on other issues is very satisfying. You're not doing the same thing a summer student did the previous year; you're actually solving a new problem.”
Although de Groote will be heading back to Belgium this month, his work at the CRIS experiment will remain. “We will certainly continue to use his model for our analyses,” says Flanagan. “He’s become part of the team during his stay, and we wish him the very best of luck.”