UWC Physicists Reach For The Stars: Excitement and Coulomb Excitation at CERN
A group of UWC students (and their professor) recently performed a major African-led experiment at the CERN laboratory* in Switzerland - using some of the most powerful scientific equipment in existence to examine sub-atomic matter and reflect on what happens when stars explode.
CERN, the European Organization for Nuclear Research, is the place where the world’s best physicists and engineers go to find out more about the basic constituents of matter - the fundamental particles that make up our universe.
Professor Nico Orce was accompanied by postgraduate students Dineo Mavela, Senamile Masango, Elijah Akakpo, Kenzo Abrahams, Craig Mehl, George O’Neill, Elias Martin Montes, and Cebo Ngwetsheni from UWC and Sifiso Ntshangase from UniZulu. All these students come from HDIs through the very successful MaNus/MatSci Honours/Masters Programme at UWC. Prof Orce was determined to give as many UWC students as possible the opportunity to the world’s most powerful research laboratory created by mankind - and they didn’t let him down.
This was a long training effort with many CERN-like experiments performed here at iThemba LABS, learning the CERN computing programs (ROOT, GEANT, GOSIA, etc.) and passing the required practical training courses and exams to enter the facility. This hard training resulted in our UWC students running the CERN experiment on their own for many a shift!
Senamile Masango had the additional honour of being the very first South African woman to conduct a physics experiment at HIE-ISOLDE.
“The experience has really motivated me to do even more,” Senamile says. “We were certainly not observers; we led this incredibly complex experiment and had amazing support from the engineers at CERN. We could see that we are not quite at their level yet, because they have spent so much more time at CERN, using their systems. But what that did was to show us just how much we could achieve in the future.”
Opening the Doors to the Stars
The team used a technique called Coulomb Excitation to determine the shape of Selenium-70 (70Se) at its first excitation. The nucleus of this isotope is known to have two possible shapes, depending on its excitation state, and the team wanted to examine the relationship between shape and energy more closely. This radioactive element decays very quickly to Arsenic-70 and then to Germanium-70.
None of the labs in Africa have the resources to accelerate exotic, short-lived nuclei such as this.
“70Se only lives for about 41 min, and it’s only produced during X-ray bursts - like the ones found most commonly in stellar explosions happening in neutron stars,” Professor Orce explains. “So far we can only accelerate stable beams at iThemba LABS, so we needed to go to CERN to complete these experiments. Soon enough we may be doing these kind of measurements for the first time at iThemba LABS - here in South Africa. That will be great!”
Why is it relevant?
“In terms of nuclear structure, there’s a unique phenomenon which happens only in nuclei,” Professor Orce explains. “Nuclei can change shapes with a very small amount of excitation energy. The phenomenon is not well understood and may influence the decay property of the nucleus - which which in turn affects how it decays to stable nuclei and, hence, accounts for the abundance of elements. In essence, we’re studying how elements are created in stellar explosions. “
So this experiment can help shed light on events that happen far from our experience, that we’d never be able to survive experiencing directly, and help us get a clearer picture of an aspect of the universe.
But why is it relevant?
“Along with the keys to the most famous scientific laboratory in the world, we’re training our students to the highest scientific standards, providing our students with the necessary technical and theoretical skills to achieve excellence in whatever they want to do in life. We’re creating role models and leaders for the country,” says Prof Orce. “We’re broadening their horizons - while at the same time helping us all see deeper into the cosmos.”
In other words, no matter how you look at it, the experiment was a huge success.
“I think it's fair to say that out leading experiment opened the door for all South Africans to have similar dreams,” Prof Orce adds. “But we cannot ignore our South African pioneers in the SA-CERN Collaboration: Krish Bharuth-Ram and Jean Cleymans, who originally opened the doors for this to happen and, in particular, Krish managed for payment of the ISOLDE fees, making it possible for all South African to lead experiments at CERN. New SA researchers are becoming CERN Team Leaders in the meantime, like Sifiso Ntshangase from the University of Zululand and more will come.”
“We are living the dream,” Cebo says. “Going to CERN is the pinnacle for any physicist, and we are really grateful to have had the opportunity.”
Want to know more? Watch the UWC-CERN collaboration video here!
*Technically, it was the first African-led CERN experiment proposed and accepted (all the way back in 2013). But it required an entirely new facility at CERN called HIE-ISOLDE. After the necessary fees were paid by the SA government in 2015, other experiments were proposed in the already existing facility of the low-energy ISOLDE at CERN. “And actually one such experiment, led by Hilary Masenda at WITS and Krish Bharuth-Ram at Kwazulu-Natal, ran a month before ours,” says Prof Orce. “But ours was the first one to be proposed and accepted and probably the one with the largest SA delegation ever!”