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UCT fridge is coldest spot in Africa

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SUZANNE BELLING

PHOTOGRAPH: ABIGAIL BLUMENTHAL

 Pictured : Associate Professor Mark Blumenthal with the dilution fridge.

In South Africa, the coldest place is the town of Sutherland in the Northern Cape, with a lowest recorded temperature of minus 16 degrees Celsius and regular snowfalls in the height of summer – although the lowest temperature ever recorded in South Africa was minus 20,1 degrees at Buffelsfontein in the Eastern Cape, near Molteno.

“These are naturally occurring cold temperatures,” according to Mark Blumenthal, Associate Professor in the Department of Physics at the University of Cape Town.

But a dilution fridge recently acquired from Holland by his department is officially “the coldest place in Africa”, with a temperature of 8,190 milli Kelvin – significantly colder than the Boomerang Nebula.

The fridge was supposed to have been installed two years ago, but on opening it, Blumenthal and his team discovered that the R6,5 million piece of equipment had been damaged in transit.

Engineers were called out from Holland to rebuild the fridge and the team worked throughout the night to assemble it with spare parts that had been delivered to Blumenthal’s home.

At present, Blumenthal and his team together with international engineers and technicians are busy refining the working of the fridge, which is one of the biggest and most powerful in the world.

The fridge will be used to study material systems and to control and manipulate single electrons, Blumenthal told SA Jewish Report.

He and his team are working with collaborators at Cambridge University in the UK and University College, London in the field of nano-electronics and are building devices which can track individual electrons and examine the spin on electrons.

Because of the size of electrons – a mere component of an atom – they need to be cooled to a very low temperature in order to slow them down to capture.

The dilution fridge has a 10 Tesla super-conducting magnet – 25 000 times more than the earth’s magnetic field. This allows the physicists to manipulate the spin of electrons.

It also has a closed cycle dry circulation system, which allows the helium 3 and helium 4, the main cooling agent of the fridge to be recycled. This is very handy given that helium 3 costs in the region of €3 000 (about R52 000) per litre and the fridge makes use of 50 litres.

A top loading probe allows samples to be loaded into the fridge allowing for quick sample turn around times.

Some of the research applications of the fridge are quantum computing, quantum cryptography and metrology which is the science of standards.

The fridge will also be used for the training of students in understanding vacuum systems, cryogenics and solid-state physics.

Blumenthal is an expert in low-temperature nano-electronics. He grew up in Johannesburg and did his undergraduate degree at the University of the Witwatersrand. He has a diploma (MSc) from the University of Bonn in Germany and a PhD from Cambridge University.

Before joining the Department of Physics at UCT, he worked at the National Physical Laboratory in London and Siemens Magnet Technology in Oxford.

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