Posts Tagged ‘Cockcroft and Walton’

The Atom Splitter: Ernest Walton


In 1932, aged 29, Waterford-born Ernest Walton, pictured here on the right, did something remarkable – he split the atom, or the atomic nucleus to be more precise, and the news stunned the world.
This colossal event in the history of science took place in Cambridge, UK, in the Cavendish Laboratory, a world-famous laboratory run by Lord Ernest Rutherford, a New Zealander. Rutherford had won a Nobel Prize for physics in 1908 and was a huge figure in science in general and nuclear physics in particular.
Walton, meanwhile, was a brilliant apparatus man, a hands-on physicist, and he had personally built the particle accelerator machine that enabled the nucleus to be split. He worked closely with John Cockcroft, who was a theoretician. They were a perfect team. Cockcroft proved it could be done, and Walton then went and did it.

Newspapers around the world reported the news, and the Albert Einstein himself called to the Cavendish Lab to congratulate Walton and Cockcroft.

For Einstein, this experiment was the first solid evidence to support his famous equation e = mc2 which held that energy and mass were linked, and that it was possible to release enormous amounts of energy – if mass could be split apart.

EXPERIMENT 
The key to the success of the famous atom splitting experiment was perhaps the inspired decision by Lord Rutherford, Head of the Cavendish, to pair the hands-on Walton, with the theoretician Cockcroft.

Rutherford, recognised the talents of the two young geniuses at his disposal, and put them together. They were very different, but complimented each other.

At this time, The Cavendish and other labs, particularly in the US were in a race to see who could split the atomic nucleus first. The general thinking at the time was that particles, protons would need to be accelerated to very high speeds, at astronomically high electrical voltages – perhaps as high as one million volts – to make it possible for them to slam into atomic nuclei and split them.

Walton had done his PhD in the generation of high voltages and this was a continuation of that work. He got the voltage up towards 800,000 volts and they decided they would try and experiment and see what happened.

Walton got the machine going and crawled back across the floor of the lab towards a lead-roofed observation box – to protect against x-rays and high voltages. The protons were being slammed into a piece of lithium metal and he took at look now at the impact. He immediately began seeing little flashes.

He was elated, as the flashes, he knew could be an indication that the lithium atoms were being split into two helium nuclei, also known as ‘alpha particles’ which had been first discovered by Rutherford himself three decades earlier. Walton immediately called Cockcroft to come, he knew something was happening. He later described what looked like ‘twinkling stars’ – lots of them.

Cockcroft arrived, and Rutherford then appeared. The two younger men manoeuvred Rutherford into the small observation hut, which wasn’t easy, as he was a big man, it was a tight space, and, at this stage, the great man, wasn’t young either.

Philip, Ernest’s son, and himself a Professor of Physics at NUI Galway (recently retired) recalled what his father told him happened next. “He (Rutherford) was shouting out instructions – ‘turn up the voltage’, ‘turn down the voltage’ and whatnot. He got out, and without saying anything at first, he walked across the room, perched himself on a stool and said: “Those look mighty like alpha particles to me – I should know, as I was in at their birth.”

The atomic age had begun.

FIGURE 
Walton was an unlikely figure to be thrown into the media maelstrom that occurred after the 1932 experiment. It changed his life forever, and at a time when most scientists are only getting their careers started he had reached his pinnacle.

He was a strongly religious man all his life –  the son of a Methodist preacher who had travelled all over Ireland and lived in many towns on both sides of the border, including Cookstown, Bambridge, Dungarvan, Armagh and Drogheda.

Sunday’s were for religious service and nothing more, whereas every other day was all about work. He was also a non-drinker, with a few close, loyal friends.

He had attended Methodist College in Belfast as a border, where he was ‘Head Boy’ and he had developed a strong affection, which was returned for the school’s ‘Head Girl’, Breda. After they left school they went their separate ways, but after a chance meeting the relationship was re-ignited and the letters flew back and forth.

He returned to Ireland in 1934, not least because he wanted to marry Breda, who was working as a teacher in Waterford. They were duly married in Dublin, and set about raising a family from their home in St Kevin’s Park, in Dartry, Dublin 6.

Walton returned from Cambridge to head up an ailing Physics department, with just three staff. His workload was huge in terms of administration, and teaching. This all mean that from the time he returned Ireland, to TCD, he did little research.

He died in 1995, aged 92, and is remembered fondly by his colleagues and family as a quiet man, who had no interest in the limelight. Often he would sit in the staff room at TCD quietly humming a tune, when a visitor would come in, and be stunned to be introduced to Ernest Walton, the giant of Physics that split the atom.

Many students will remember him as a brilliant teacher, who often performed experiments on the bench, in front of the students during a physics lecture. His son Philip, the recently retired Professor of Physics at NUI Galway, recalls that his father spent many long hours in the attic at home, after dinner, preparing his lectures.

Others will remember him at the Young Scientist Exhibition in the RDS for many years, when he could be found in teacher mode surrounded by an enraptured audience. For ETS Walton, teaching was a very important part of the scientist’s job.

To this day he remains the only Irishman who has been awarded a Nobel Prize in any field of science. That was in 1951, 22 years after the atomic nuclei was split.

This article was first published in the May-June issue of Science Spin

How Irish Scientists Changed the World, by Seán Duke, is due for publication by Londubh Books in 2012.

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