Local students play a part in Swiss physics project
In 2012, many people were astonished by the announcement by the Centre for Nuclear Research (CERN) in Switzerland of the discovery of the Higgs boson.
The discovery completed physicists’ understanding of that part of the world that can be seen and felt — normal matter. It inspired physicists to study a whole new world, searching for answers to the mysteries of the things in the universe that can’t be seen.
“Normal matter, the things that we can see and feel around us, comprises only about 4% of what is actually in the universe. While we know that there is a lot of matter and energy out there we do not really know what it is and how it is related to the known matter,” says Prof Bruce Mellado of the School of Physics at the University of the Witwatersrand (Wits), who is also the national contact physicist of SA at the ATLAS experiment at CERN.
ATLAS, one of the largest collaborative efforts ever attempted in particle physics, is exploring the basic building blocks and fundamental forces of nature.
The Department of Science and Technology funds the country’s CERN consortium. It is an essential avenue for students and researchers to access this leading global research infrastructure.
Wits is the single largest contributor from SA to CERN, providing theoreticians, experimentalists and 35 students from a wide variety of backgrounds who are very involved in the search for new bosons.
The students spend significant amounts of time at CERN, where some play an active role in the upgrading of the ATLAS particle detectors situated in the Large Hadron Collider (LHC).
The LHC will be upgraded in 2023-2024 to enhance the potential for new discoveries.
“The LHC is the largest particle accelerator in the world and it is used to accelerate two high energy particle beams in opposite directions in a circular route and set them on a collision course with each other,” says Nthabiseng Lekalakala, a master’s of science student at Wits who is based at CERN.
“By colliding the particles against each other at speeds close to the speed of light, we physically break up these particles to see what they are made of.”
These collisions happen at a rate of one every 25 nanoseconds — one thousand-millionth of a second.
Dingane Hlaluku, a student at the Wits School of Physics, is working on the software upgrade of the detector. He completed his master’s in physics at Wits in 2017 and has developed a keen interest in software engineering of largely distributed systems.
In October 2017, he was invited to deliver a plenary talk on the status of the detector upgrades to the tile calorimeter of the ATLAS experiment, an event that included some of the world’s top physicists in highenergy physics.
Mellado says Hlaluku’s presentation was “an honour” to all the South Africans involved in the project.
One of the biggest challenges at the ATLAS experiment is sifting through the huge amounts of big data it delivers and capturing only relevant data. This is where Hlaluku’s software update plays a crucial role.
After the upgrade, the readout electronics will need to cope with digital data with full granularity at about 40MHz, which means the electronics will need to process data at a minimum rate of 9.6 gigabytes per second to the off-detector read-out components.
This is equal to downloading three full feature-length Blu-ray DVDs per second. The offdetector electronics used to control, configure and monitor the process will be required to send data at a rate of about 4.8 gigabytes per second.
“The software is augmented to look for specific signatures from different regions of the detector in three stages and discard uninteresting events in real-time,” says Hlaluku.
In the current configuration of the detector, data is processed, digitised and read out at 100KHz.
The fourth annual highenergy particle physics workshop took place at the end of January at the Wallenberg Research Centre at Stellenbosch.
Professor Alan Cornell from Wits University, a co-chair of the workshop, has been instrumental in the growth of the field in SA.
“It is great to see so many new students choose to do research in our field. The attendance at this year’s workshop was double that of three years ago,” says Cornell.
Another Wits student contributing to the upgrade of the hardware for the ATLAS detector is PhD student Joyful Mdhluli, 24.
She has been involved in the CERN for two years and says the experience has changed her life. “I’ve been able to attend lots of conferences, where I’ve met different kinds of people from different parts of the world, and I’ve also learnt a lot about highenergy physics,” she says.
“I realised that high-energy physics involves a lot of interesting stuff, like astronomy and dark matter.”
In her research, Mdhluli is trying to find materials that can withstand high levels of radiation for parts of the ATLAS detector. “If you want to study particles beyond the standard model, you need to get efficient and accurate data, so if the materials in the detectors deteriorate over time, then that means the signals they get over time are not reliable,” she says.
“So we are trying to make it as efficient as possible by making sure that the materials they are using will be able to last long periods and will have reliable signals coming through,” says Mdhluli.
Prof Elias Sideras-Haddad, Mdhluli’s PhD supervisor and a member of the ATLAS experiment, is enthusiastic about training students in nuclear and radiation physics.
“The ATLAS experiment operates under high levels of radiation. SA has excellent capabilities to understand how detector components respond to radiation,” he says. “Our work with the ATLAS experiment opens a new dimension and demonstrates that SA has a lot to offer.”
Wits’s involvement at CERN has led to technological innovation in SA. Cape Townbased company Trax Interconnect built a new 16-layer electronics board for the ATLAS detector upgrade. Until recently, it was the most complex printed circuit board produced in SA.
“The production of the board for ATLAS was a challenge. Since then, we have improved on our capabilities and now we are able to produce even more complex boards,” says Trax International MD Daniel Dock.
Speaking at the high-energy particle physics workshop in Stellenbosch, Mathis Wiedeking of iThemba Laboratories said SA had a long-standing collaboration with CERN.
“Student training and the education of our nextgeneration scientists is a top priority and a foundation for research development.
“SA plays a visible role in this field of research and contributes quite significantly,” he said.
“The SA-CERN consortium has the capacity to attract young people and get kids interested in science, and plays a huge role in sparking interest in science and technology among young South Africans.”
Mellado agrees. “Our collaboration with CERN provides us with an excellent opportunity to develop human capacity in areas of high-tech that are badly needed in SA, contributing to the training of a new generation of leaders. Technology transfer to South African industry is an important by-product of this interaction.”