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Battle with the WIMPs at Boulby Mine.

(from RAL `LABNEWS', February 1998)

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John Battle MP, Minister for Science, Energy and Industry visited the Cleveland Potash Boulby Mine, site of the world class UK dark matter experiment, last month. Key scientists from the collaborating groups (Dr Neil Spooner from the University of Sheffield; Professor John Quenby from Imperial College, London and Professor Peter Smith from RAL, the project leader) demonstrated the methods used to investigate the presence of `dark matter' in the universe. The Minister also had the opportunity to see Cleveland Potash's mining operation.

Every spiral galaxy is surrounded by unseen matter which holds the stars in place by gravity and prevents the whole system from flying apart. Cosmologists believe that this `dark matter' is so common that it makes up to 99 per cent of the universe. One idea is that it consists of tiny sub-atomic particles, known as WIMPs (Weakly Interacting Massive Particles) and the UK Dark Matter collaboration is actively researching ways of detecting these.

WIMPs are difficult to distinguish from other cosmic particles bombarding the Earth and this is why the research work is carried out at Boulby, the deepest mine in Europe. The mine has large workings at a depth of 1,100 metres, with the dark matter experimental areas situated in two large caverns hewn from the rock salt layer which sits just below the potash ore seams. This makes the site possibly the best in the world for undertaking a search for WIMP dark matter, since it is both deep enough to stop the cosmic rays and also, thanks to the nature of the salt, low in natural radioactivity. The detecting equipment is suspended in 200 tonnes of high purity water to shield the dark matter detectors from this background radiation.

A visit down the mine is quite an experience writes Andy Kurzfeld. Kitted out with full safety equipment - helmet with miner's lamp, belt with battery and self-rescuer (a carbon monoxide filter system), both of which are pretty heavy, and steel toecap boots - we were advised to wear the minimum under our company overalls. Then into the cage for the journey down the shaft to the working levels - at a speed of about 17 mph - and from the bottom of the shaft by transit vehicle along some of the 400 km of roadways that exist underground in a rabbit warren of mined areas, some of which spread out under the sea to a distance of 5 km.

Conditions underground are not the most pleasant, with temperatures which can often reach 42C in the dark matter experimental areas. In fact it was only about 35C during our visit but this was draining enough when just walking aroun - and when manual work is involved............. well let's just say that the supplies of water are essential! That the caverns are in the rock salt brings with it two bonuses: the salt layer is inherently more stable and the salt does not fly round as much as one might expect so, notwithstanding a slightly salty taste on the lips and a thin layer of salt on every available surface, the air quality is reasonable.

But this is in real contrast to the potash ore mining area where there are a number of extra little things to contend with. The airborne dust levels are much higher. Caught in the beams of light from the headlamps these looked just like a very fine sleet and required the use of dust masks. The dust is worse still when the mining operations are taking place and this is accompanied by the deafening sound of multi-tungsten carbide tipped drill heads drilling into or devouring the potash ore face. In addition the shaft roofs are unstable with side supports designed to collapse to warn of any problems. No wimps, the miners, that's for sure and the contrast between the company's mining operations and the research project could not be clearer.

As part of the visit, Mr Battle presented a plaque to Cleveland Potash Ltd in recognition of the company's continuing commitment to the research project. Mr Battle commented "The science of dark matter is extraordinary and fascinating. I am delighted to have this opportunity to see for myself the progress the team is making in its search for dark matter particles. This is a spectacular example of how well-established industry and leading edge scientists can work closely together. By making their mine available, Cleveland Potash Ltd have ensured that British scientists have access to some of the best conditions in the world for their research."

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j.d.lewin@rl.ac.uk - May 19th, 1998

URL: http://hepwww.rl.ac.uk/ukdmc/databases/pr/battle-rl.html