Gandalf meets Hawking? Africa’s first deep underground lab to shed light on dark matter

Does a laboratory the size of four Olympic swimming pools in the depths of the Western Cape’s Du Toitskloof Mountains sound like Lord of the Rings and Stephen Hawking’s theory on dark matter rolled into one?

Well, the Paarl Africa Underground Laboratory (PAUL) accessed via the 4km-long Huguenot Tunnel could become a reality in the next five to 10 years. The tunnel lies 800m underneath the Du Toitskloof Mountains between Paarl and Worcester.

Paarl Africa Underground Laboratory project officially launced

Already a decade in the planning, the future laboratory would be a first for Africa, and only the second such laboratory in the southern hemisphere after Australia’s Stawell Underground Physics Laboratory.

The PAUL project − which could become a reality in the next five to 10 years − was officially launched following a week-long international symposium in mid-January.

What are deep underground laboratories used for?

Dark matter makes up 85% of the universe mass, but − despite physicist Stephen Hawking’s controversial 1974 theory that dark matter might consist of substances from black holes − its particular nature is still unclear. 

Since the 1970s, deep underground laboratories have been used to search for the subatomic particles that make up dark matter, such as neutrinos and muons, and to study them 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, among others, double beta decay, geoneutrinos, reactor neutrinos and dark matter particles.

ALSO READ: Astronomers find the ‘impossible’: A galaxy without dark matter

PAUL project in the making since 2011: From SA’s gold mines to Huguenot Tunnel

Professor Richard Newman, a nuclear physicist from Stellenbosch University’s Department of Physics who is managing the PAUL project, explained in a release issued by the university, that the physics community in South Africa have been investigating the establishment of such a laboratory since 2011.

A consortium of scientists first considered options in South Africa’s very deep gold mines.

Back in 1965, the South African physicist Friedel Sellschop and the United States Nobel Prize winner-to-be, Frederick Reines, made the world’s first observation of a naturally occurring neutrino particle in an East Rand mine, some 3km below the surface.​

Only recently did the physics community start to consider the viability of the Huguenot Tunnel 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.

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Underground laboratory for SA, Africa: Why dark matter matters

Professor Newman said 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 explained in a release issued by the university.

Professor Lerothodi Leeuw, an astrophysicist from the University of the Western Cape’s Department of Physics and Astronomy, and part of the organising committee, also emphasised 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 added.

ALSO READ: Chinese satellite closes in on dark matter mystery

What next?

In order to get the project off the ground, the Department of Science and Innovation (DSI) has provided seed funding for a feasibility study for the construction of an underground laboratory with a volume of about 10 000 cubic metres.

According to chief director of astronomy at DSI Takalani Nemaungani, 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”.

Bigger societal benefits of underground physics laboratory

Professor Faïrouz 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.”