The PAUL project was officially launched in the aftermath of a week-long international symposium at Du Kloof Lodge last week, during which current and future research projects and collaborations with other deep underground laboratories around the world were discussed. The Symposium on Science at PAUL took place from 14 to 18 January 2023, and included a visit to the proposed site.
Already a decade in planning, the future Paarl Africa Underground Laboratory would be a first for Africa, and only the second such laboratory in the Southern hemisphere after Australia's Stawell Underground Physics Laboratory. Currently there are a dozen such underground laboratories in Asia, Europe and North America.
Prof. Sibusiso Moyo, Deputy Vice-Chancellor of Research, Innovation and Postgraduate studies at SU, says that PAUL, once fully implemented, will be a game changer for universities in the Western Cape, South Africa, Africa, and its partners.
"It has been great this week to see the interest from the local and international physics communities for this initiative. Thanks to support from the Department of Science and Innovation, our physicists were able to benchmark their work with physicists from world class laboratories. This will assist us with the long-term planning, implementation, and building of an ecosystem of research in this exciting field, leading to benefits for surrounding communities through the creation of new jobs and opportunities for research and skills training."
What are deep underground laboratories?
Dark matter makes up 85% of the universe mass, but its particular nature is still unclear. Since the 1970s, underground laboratories have been used to search for it and to study neutrinos in radioactive-free environments.
It is only in these underground laboratories, with a thick layer of rock shielding sensitive detection equipment from unwanted background signals produced by cosmic ray showers, that scientists can differentiate the interaction of these rare particles from the noise above. These so-called extremely rare events include, amongst others, double beta decay, geoneutrinos, reactor neutrinos and dark matter particles.
Prof. Richard Newman, a nuclear physicist from Stellenbosch University's (SU) Department of Physics and co-chair of the organising committee for the symposium, says the physics community in South Africa have been investigating the establishment of such a laboratory since 2011 - first considering options in South Africa's very deep gold mines. Back in 1965, the South African physicist Friedel Sellschop and the Nobel Prize winner to be, Frederick Reines, made the world's first observation of a naturally occurring neutrino particle in an East Rand mine three kilometres below the surface.
Only recently did the physics community start to consider the viability of the Huguenot tunnel, a four-kilometre-long road tunnel 800 metres underneath the Du Toits Kloof mountain between the towns of Paarl and Worcester, for such an underground laboratory. It is the longest road tunnel in South Africa, managed by the South African National Roads Agency Limited (SANRAL). Due to high traffic volumes, SANRAL is planning to upgrade the North Bore tunnel to lower traffic volumes in the existing South Bore tunnel. An engineering feasibility study will investigate the viability of an underground laboratory as part of this expansion programme.
A 2015 study by the environmental radiation research groups at SU and iThemba LABS confirmed that the environment of the site is appropriate for such an experimental facility. Further research is ongoing to assess the scientific contribution PAUL could offer the international community and related fields, such as biology, the geosciences, chemistry, mining technology, and underground construction and architecture.
Newman says there is a plethora of reasons to justify the establishment of such a facility in South Africa and Africa: "From a scientific perspective, for example, we would be interested in how an experiment of direct dark matter in an underground laboratory in the Southern hemisphere will compare to a similar experiment in the Northern hemisphere," he explains.
Prof. Lerothodi Leeuw, an astrophysicist from the University of the Western Cape's (UWC) Department of Physics and Astronomy, and part of the organising committee, also emphasises the importance of another underground laboratory in the Southern hemisphere: "PAUL will be in a strategic position to test, for example, the seasonal modulation in the detection of dark matter that has been predicted to be in phase with detections by direct dark matter experiments in the northern hemisphere."
PAUL will also establish strong collaborations with the radio astronomy probe of dark matter by South Africa's MEERKAT, HERA and SKA mid-array observations: "South Africa is already heavily involved with the indirect measurement of dark matter. Combined with direct measurements from a future PAUL, it may shed light on new physics," Newman adds.
Prof. Shaun Wyngaardt, head of SU's Department of Physics and part of the core task team, says as a multi-disciplinary laboratory, PAUL would be of great interest to radio biologists (health, medicine), geophysics (mining, civil engineering, agriculture and water), as well as provide spin-off opportunities in engineering and technology development.
Prof. Robbie Lindsay from UWC's Department of Physics and Astronomy and an executive member of the PAUL project, says students will benefit greatly from training opportunities and exposure to international collaboration and partnerships.
The way forward
In order to get the project off the ground, the Department of Science and Innovation (DS) have provided seed funding for a feasibility study for the construction of an underground laboratory with a volume of about 10 000 cubic meters. It will take another five to ten years to get final approval and materialise.
During his welcoming address, Mr Takalani Nemaungani, chief director of astronomy at DSI, said the data that would be acquired from an underground laboratory would supplement other data from the SKA, thereby providing the link to what physicists call multi-messenger astronomy.
In a discussion of the critical success factors for high-technology infrastructure projects, Dr Rob Adam made a comparison between the successes and failures of large projects such as the Square Kilometre Array (SKA) Radio Telescope, the Reactor Conversion Project, and the Pebble Bed Modular Reactor (PBMR). Adams is the former managing director of South Africa's Square Kilometre Array (SKA) Radio Telescope.
During the symposium local and international physicists and postgraduate students discussed proposed research projects at PAUL, and how their current research at other underground laboratories could benefit from research collaborations.
Prof. Fairouz Malek, director of research at France National Institute for Nuclear and Particle Physics, and chair of the organising committee, said the ideal for an underground physics laboratory in South Africa and Africa is also about the bigger societal benefits associated with it: "Of course we are looking forward to doing some interesting underground physics, but this initiative is also going to create so many additional opportunities for young physicists, engineers, and technicians." Prof. Malek was recently appointed as an extraordinary professor in SU's Department of Physics.
Prof. Sean Paling, director of the Boulby Underground Laboratory in the United Kingdom, said the science in underground laboratories has evolved to include unique and important studies in pure and applied particle physics, earth and environmental science, biology, and engineering: "There is a great range of science now taking place in underground laboratories, which also makes these special places ideal for science outreach and education initiatives. I have no doubt about the significant societal value that would be gained from the establishment of an underground laboratory in South Africa."
Prof. Jochen Schieck, director of the Institute for High Energy Physics at the Austrian Academy of Sciences, emphasised that each underground laboratory has a unique offering to make depending on its location and geological environment: "For scientists, the size of the experiment does not say anything about its scientific potential. Some questions can only be addressed with large experiments, others with tabletop setups. At the end you have to bring the puzzle pieces from all the experiments together to unlock the final puzzle from the universe."
Prof. Elisabetta Barberio, director of the ARC Centre of Excellence for Dark Matter Particle Physics in Australia, emphasised the importance of good science communication to enthuse the public's interest in the hunt for dark matter, thereby inspiring a new generation of innovative thinkers. In the runup to the construction of the Stawell Underground Physics Laboratory, for example, local schools experienced a 50% increase in enrolments in science-related subjects.
Dr Jodi Cooley, executive director of SNOLAB in Canada, said they are keen to support the establishment of a deep underground laboratory in South Africa: "It is one of our strategic objectives at SNOLAB to share our knowledge and expertise with the rest of the world, and we are excited about the possibilities of collaborating with another laboratory in the Southern hemisphere."
Research Report:Paarl Africa Underground Laboratory (PAUL)
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