Up and atom

If you’re planning to attend Monday’s Centenary talk on the Large Hadron Collider, you can spot a few of its distant ancestors as you pass through the Making the Modern World gallery en route to hear Brian Cox speak.

Looming large on the left of the central walkway is the cascade generator from John Cockcroft and Ernest Walton’s million-volt accelerator. This generated 1.25 million volts to accelerate protons and smash them into atomic nuclei, breaking the nuclei apart. During the Second World War this apparatus was used to study uranium and plutonium, contributing to the Manhattan Project.

Detail of the cascade generator (Image: Science Museum)

Detail of the cascade generator (Image: Science Museum)

The million-volt accelerator is a souped-up version of the appartus that Cockcroft and Walton used to split the atom in 1932, the first time this had been done in a controlled situation. This work, which earned them a Nobel Prize, provided the first experimental proof of Einstein’s famous equation, E=mc2. You can see this accelerator in miniature on the gallery’s model walkway (parts of the real thing are at our Wroughton store).

Model of Cockcroft and Waltons laboratory - spot the scientist in the shielded cabin to the right. (Image: Science Museum)

Model of Cockcroft and Walton's laboratory - spot the scientist in the shielded cabin to the right. (Image: Science Museum)

As you can tell from the size of the person in the model, this equipment was large and unweildy. Meanwhile in America, Ernest Lawrence and his student M. Stanley Livingston had been working on ways of repeatedly passing particles through the same accelerating voltage, to get a bigger overall effect. Lawrence proposed using magnets to whirl charged particles around in an ever-increasing spiral, so that they could keep crossing the same voltage gap  (his patent diagram helps explain it). The cyclotron, as the device came to be known, could split atoms in equipment that fitted on a laboratory bench.

In 1931, Livingston passed the magic million-volt mark with an 11-inch cyclotron, which prompted an excited telegram from the lab to Lawrence: “Dr Livingston has asked me to advise you that he has obtained 1,100,000 volt protons. He also suggsted that I add ‘Whoopee!”.  You can see an early example of this whoopee-inducing device in the bench case opposite Cockcroft and Walton’s cascade generator. Shortly after Cockcroft and Walton, Lawrence also succeeded in splitting the atom, and the invention of the cyclotron earned him a Nobel gong too.

Early cyclotron designed by Lawrence, 1932

Early 11-inch cyclotron designed by Lawrence, 1932

These early atom-splitters ushered in the age of Big Science, with particle accelerators getting bigger and bigger as physicists continued their quest to probe ever-higher energies. And as I’ve mentioned previously, the Large Hadron Collider is the biggest of big. Hope you enjoy the big ideas in Professor Cox’s talk!

4 thoughts on “Up and atom

  1. Simon Jones

    You used to have a one million volt generator which used to emit loud bangs. Is this the same thing

    Reply
    1. Alison Boyle Post author

      No – I think you’re remembering the Van de Graaf Generator that used to be in Launch Pad?

      Reply
      1. Simon Jones

        Thanks Alison, I remember the Van de Graaf Generator, but this was big going up to the ceiling. When it went bang you knew about it and a spark would jump between 2 points. Visitors were warned that if they did not like loud bangs to go to another floor. It was situated I think where Making of the Modern World is know and was in its own enclosure. Could it have been a Marx Generator, as they are similar in pictures that I have seen.

        Reply

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