Rear Window: Smashing the atom: The first 'big physicists' did it in a tea chest

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The Independent Online
THE SCIENCE of nuclear physics passed a milestone last week when it was announced that evidence had been found of the existence of the top quark, last of the 12 essential building blocks of matter to be identified.

If confirmed, this will be a triumph for the extraordinary, esoteric and expensive discipline known as atom smashing, in which particles are hurled at one another at incredible speeds to see what happens.

The machine used to find the evidence revealed last week is at the Fermi National Accelerator Laboratory in Illinois. There, particles are spun in a racetrack four miles in circumference, and the 'events' that occur when they collide are recorded by 5,000 tonnes of detecting equipment. More than 400 scientists are involved, and many millions of dollars.

The first atom smasher, by contrast, was built by two men at the Cavendish Laboratory in Cambridge using car batteries, putty, parts from petrol pumps, a microscope and a wooden box like a tea chest. The bill, regarded at the time as extravagant, ran to several hundred pounds.

The two were John Cockcroft, from a Lancashire mill- owning family, and Ernest Walton, son of an Irish Methodist minister. Their machine, which produced its first results in 1932, won them the Nobel Prize for physics. The Nobel committee said they ushered in 'a totally new epoch in nuclear research': where previously scientists had only been able to observe the breaking up of atoms through natural processes, they now had a tool to split them at will.

It was the fruit of three years' work, including a setback in 1930 which forced them to return to square one. Cockcroft (later Sir John Cockcroft) provided much of the scientific innovation, while Walton, deft and ingenious, did most of the practical construction.

In the spring of 1932, when they became bogged down in tests and calibration, they received a visit from their supervisor, the pioneer of nuclear physics, Lord Rutherford. He looked at the machine, heard their reports and declared with irritation: 'Nobody's interested in these measurements you are taking. Get on with it and see if these particles will actually do anything.'

The next morning Walton turned on the Heath Robinson array as usual and, amid the rumble of vacuum pumps, the humming of generators and the crackling of sparks, set in motion a beam of protons whipped to high speed by 600,000 volts.

Clambering into the wooden box he examined through a microscope the effect of this beam on a 'target' of lithium. Tiny flashes told him something remarkable was happening: lithium atoms, struck by the protons, were splitting into two equal parts - helium atoms.

Within days, Cockcroft and Walton were famous; the subject of newspaper articles, cartoons and editorials. The Daily Mirror, for one, was concerned about the atom: 'Let it be split,' the paper said, 'so long as it does not explode.'

The era of 'big physics' had begun. In laboratories across the world, plans for bigger, better atom-smashers were immediately laid and today, even after last week's claimed discovery, that era is set to continue. Next month the member nations of the Cern European research group meet to decide whether to build a machine in Geneva even more powerful than Fermilab's, with a 17-mile racetrack, that will cost about pounds 1bn. One of its tasks will be to find an entity even more elusive than the top quark: the Higgs boson. If it is there, it may tell us why matter has mass.

(Photograph omitted)

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