Professor John Newton, nuclear physicist

Nuclear physicist

Professor John NewtonJohn Oswald Newton was born in 1924 in Birmingham, England. He won a scholarship to St Catharine’s College, Cambridge, where he completed the first two years of his bachelors degree (BA, 1944) before joining the war effort in 1943. During WWII Newton worked as a junior scientific officer at the radar facility in Malvern. In 1946, he was able to return to the Cavendish laboratory at Cambridge to finish his MA (1948) and later his PhD (1953).

Newton joined the Atomic Energy Research Establishment (AERE) in Harwell in 1951. He began as a fellow before promotion to principal scientific officer in 1954. Newton then accepted an appointment as senior lecturer (1959-67) and later, reader in physics (1967-70) at the University of Manchester. The first of Newton’s visits to the Lawrence Radiation Laboratory (LBL) in Berkeley, USA took place in 1956-58. He made subsequent visits in 1965-67, 1975 and 1980-81.

In 1970, Newton left England and became professor of nuclear physics and head of department at the Australian National University (ANU), Canberra. Newton was instrumental in the installation of a new accelerator at the ANU and introduced a new collaborative research ethos to the department. He was made emeritus professor in 1990 and continued as a visiting fellow in the Department of Nuclear Physics until 2008.

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Interviewed by Professor George Dracoulis in 2010.

Contents


Humble beginnings

So, John, can you tell us something about your family background—conditions at home and what it was like growing up?

I was born in 1924 in a rather poor suburb of Birmingham and my parents were not very well off. They lived in two rooms, rented in somebody else’s house. Later we moved to a corporation house, like a government house here in Australia. My father was a very intelligent man, but regrettably he had to leave school at the age of 14. He was also intensely shy, which unfortunately I inherited from him—and that’s been a burden for me throughout my life. He and my mother worked at the Dunlop Rubber Company, he as a clerk and she as a bookkeeper. I was an only child. I had a very happy childhood, much of it spent playing with other kids in the street, which one did in those days.

That was during the depression, wasn’t it?

That’s true. I lived through the Great Depression, which was a terrible experience. Every day when I met my father coming back from work, I asked him whether he’d had the sack— fortunately, he never lost his job.

When you went to primary school, you were quite young?

I went at the age of five, and the primary school was quite close to where I lived. They had graded classes, from A to D, in descending order of brilliance. I was in the A class, but I didn’t find it very stimulating, in spite of that. Probably one of the reasons for this was that many of the pupils were poverty stricken and I guess their parents didn’t give them much help in their schooling. I did well in that school and skipped one year, enabling me to leave at the age of 10. Consequently I was usually the youngest person in the class at all my later schools and at university.

Did you go from there to grammar school?

Yes. My parents had a rudimentary education but wanted to ensure that I had a good one. They enrolled me in Bishop Vesey’s Grammar School, which was in Sutton Coldfield and was founded in 1540. It had boarders as well as day students. It was not a wealthy school, but a good one. It required fees, which my parents couldn’t afford, but I managed to get a County Minor Scholarship, which paid them.

In the first four years at school, leading to the School Certificate, I took eight different subjects. In 1938 I took these in the school certificate examination, which I passed. They had sport at school as well. It was rugby in the winter, which I disliked intensely, cricket in the summer, and also running, at which I was quite good.

Did your teachers at primary school encourage you?

Not really. They were generally good, but didn’t inspire enthusiasm for anything in particular. My liking for science, which developed quite early, must have come more from within myself rather than from any external stimulation.

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A Chemistry set, Meccano, Radio and Chess

Perhaps you had hobbies outside of school, John, which stimulated your interest in science?

Yes. My parents bought me a chemistry set and I had great fun with that, making smells, explosions, etc. One of the things that I particularly wanted to do was to make fuming sulphuric acid, which the instructions said you could do. But I never succeeded, which perhaps was fortunate—and that’s maybe why I’m still here.

I had another toy, a Meccano set, which I think is one of the best toys ever invented. It consists of a lot of strips of metal with holes in them, which you can screw together, and various accessories, like wheels and clockwork motors; so you could make a variety of models. It gave great scope for the imagination. Also, I think it helps one with engineering skills. I started off with a very little one; but you could get additional “add-on” sets, and it gradually built up.

I had a Meccano set too. In fact, I’ve still got parts of my Meccano set at home. I passed that on to my son many years later.

Good. Was he interested in it?

Oh, yes. Well, he’s a graphic designer now. But he was interested in building things out of the Meccano set and also the more modern varieties of those things, because there was a German version that was quite good—But I am probably deflecting you from your story, John.

Oh, that’s fine. Another thing I was very interested in was radio. At that time, you could buy valves pretty cheaply second hand; you had to use them as there were no transistors. So I made radio sets with them. I made a shortwave receiver so that I could listen to stations all over the world. I listened to Hitler’s speeches, which were rather terrifying; I couldn’t understand a word, but he drove his audience into a frenzy. Later on during the war, I was able to listen to German propaganda too.

A school-friend of mine introduced me to classical music, which soon appealed to me much more than pop-music. It became very important throughout my life, giving me both mental uplift and relaxation.

My father was a good chess player and he taught me the game. I was quite enthusiastic about it. I played at school and had some very long games, some lasting about eight hours. Eventually I did quite well. I went into the Warwickshire Junior Championship and won it on the second attempt. This entitled me to go into the British Boys Championship the following year; so in 1940 I went to take part in that. Unfortunately, it occurred immediately after the Higher School Certificate examinations, which left me very tired. The long and tedious journey to Hastings did not help. In spite of this, I did very well in winning my heat, which entitled me to go into the final round. But, by the time I got to the final round, I was so exhausted that I really didn’t do very well at all. In one game—it was really a ‘won game’—I offered a draw because I knew I would lose it by making some silly mistake. Anyway, I came sixth in the championship and was offered the choice of having a nice chess book with a beautifully inscribed plate or money. I took the money (ten shillings) so that I could buy a dynamo set for my bicycle.

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Road to Cambridge

That was probably a good choice, I think. And what of the later years in grammar school?

After the School Certificate, I had the choice of going into either arts or science, and I chose the science option. I went into the sixth form, which was mainly for students who wanted to go to university. At that time, only about five per cent of children went to university — a small percentage compared with now. I enjoyed the courses very much. The chemistry and maths teachers were very good and both of them inspired me. Chemistry became my favourite subject. Unfortunately, the physics teacher was not so good. He used to sit down in front of the class with a textbook and read it to us. I could have got more out of it by reading it myself.

That sounds very much like my chemistry teacher in my final year at high school; he did the same thing and we essentially copied out his prac book. So I didn’t like chemistry. We had a good physics teacher, though.

Well I didn’t like physics for the same reason.

Well, there you are: it all goes to the teacher.

I agree.

So you were keen to go to university?

I was keen to go, as were my parents. In fact, they wanted nothing less than Cambridge University, which was quite a task.

Perhaps not many kids aspired to go to university, certainly not kids of your background.

That’s exactly right—and very few did; they wouldn’t even consider it. So I think I was very lucky that I had parents who encouraged me and supported me all the way. To go to Cambridge, you first had to be accepted by one of the Colleges in Cambridge; they wouldn’t accept you at the university otherwise. One of the ways to do this was to go and take the College scholarship examinations, which they held every year. At my school there was no special teaching for these examinations, so I used to sit in with the second year sixth form and the teacher used to talk to me occasionally, when he had time, and give me some problems to do. This put me at a disadvantage to kids who went to some of the very best grammar schools and the public schools, which were just for rich people, and had special classes to achieve it. I passed my Higher School Certificate after the two years and then spent a further year preparing for the scholarship examinations.

The scholarship examinations were held in Cambridge; is that right?

Yes.

So you eventually went to Cambridge; had you been there before?

No, I hardly travelled anywhere else before. So it was really a revelation—fantastically beautiful buildings, and you went to dinner in a very impressive hall and the waiters were all in evening-dress and served a magnificent meal, even though it was wartime. So the whole thing was really remarkable to me and very impressive indeed.

Two College Fellows told me that I did well in the scholarship examination and they would like to have me. I got my first formal invitation from St Catharine’s College. I accepted it on the condition that I would get a State Scholarship—because my parents couldn’t afford to send me there without a scholarship. I then had to prepare for the State Scholarship, and that was done by taking the Higher School Certificate examination again, together with a set of special scholarship papers. It was a competitive examination, but I passed it. My maths teacher congratulated me on this achievement. I got my State Scholarship, which paid for the university fees and about £175 per year for living expenses at the college. That seemed to be quite a lot, but Cambridge was an expensive place.

That was quite a lot of money in those times, I think.

Yes, it was.

So you eventually then went to Cambridge, having got a scholarship. Were your early impressions accurate?

Well, mostly, but not quite. Unfortunately, I got the worst room in the college. This was a very cold room; it had very thin walls. In the sitting room there was a hole in the wall and you could look outside and see the traffic in the street. Like in most College buildings there was no running water. A College servant brought a jug of hot water for washing each morning. To go to the toilet or have a bath, I had to walk across two courtyards. The bedroom was below the sitting room and there was a high wall that came up almost to the level of the window. Below that, there was a butcher’s yard and he used to throw his rotting meat into it. When I first went into the bedroom, I thought, ‘Oh, it smells rather musty in here; I’ll open the window to get some fresh air’—I won’t say any more about that.

Did they save that room for you, John?

It seems so.

Was it a stimulating atmosphere in Cambridge?

It was a very stimulating atmosphere and it was also very good for a person who came from a very narrow cultural background. In the college, where everyone lived together, there were students and College Fellows from many different disciplines. Talking and interacting with them broadened one’s outlook a great deal. I think that was very good for me.

For the first two years it was a fairly general course, with a choice of a number of subjects, leading to the Natural Science Tripos examination. I took physics, chemistry, mathematics and mineralogy, to start with. However, chemistry ceased to be my favourite subject because it involved endless amounts of memory work. I’ve never been very good at memory work, although I was quite good at working things out. My enthusiasm for physics increased considerably because the courses were very good. At that time, the lecturers came in with an assistant in a white coat and the assistant used to set up some experiments, which were exciting. I think that raised my enthusiasm and made the whole lecture more interesting. There were some very good lecturers at that time.

The Cavendish lab was very close to my College. It was in an old black building where there was still an aura from the great physicists who used to work there—like Rutherford, Maxwell, etc—and I found that quite stimulating.

When you were doing your courses at Cambridge, they introduced electronics, which I think was a new subject at the time.

It was an entirely new course; it hadn’t been given before. I didn’t realise at the time why it had been introduced. It was because of the development of radar, and the need to train people to work in it. I was always very interested in radio, so it was a great thing for me and I accepted it with enthusiasm. There were very young and enthusiastic lecturers too, which was very good. I probably should have given up some other subject to take electronics—but I didn’t, and that was perhaps unwise. Anyway, it was worth taking electronics; I’ve never regretted that.

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War time work on radar

This interest in radar and electronics and Cambridge itself, in fact, led you to Malvern. How did that come about?

During the war, they allowed you to do only two years of the normally three-year course. After that, all the science students were interviewed by a board in order to be assigned to various war activities. I was interviewed by a board chaired by CP Snow, who was a famous author and also a scientist. He assigned me to the Air Ministry research establishment at Malvern, which worked on radar. It was called the Telecommunications Research Establishment (TRE) to mislead the enemy; there were lots of aerial arrays around and, if the Germans saw them, they might have guessed the true purpose of the Establishment.

How did radar develop at that time?

In 1935, Hitler came to power and started building up an enormous war machine. The British government began to get worried about it, and one of the officials in the Air Ministry decided that he would like to make a radio ‘death-ray’ to shoot down enemy aircraft—

It sounds like Ronald Reagan.

Yes—and he wrote to Watson-Watt, a physicist who worked on the ionosphere, and asked for his opinion. Watson-Watt didn’t think that the death-ray was a very good idea. Instead, he suggested that one might detect enemy-aircraft by having two radio transmitters sending out signals, which would be reflected back from the aircraft. If you measured the time taken for the signal to get to the aircraft and back, you would know the distance and, from triangulation, where the aircraft was. So this really was the beginning of radar—in Britain, anyway.

A significant scientific and industrial effort was put into this. By 1939, at the beginning of the war, there was a chain of 19 radar stations, working on a 10­meter wavelength, established all around the East coast of Britain. These stations were powerful and could see enemy-aircraft take off from the coast of France. But it wasn’t sufficient just to have these radar stations. You had to assemble the data and correlate it so that you could tell the fighter squadrons where the enemy was, where they were going and so on. This was almost an equally important part of the system. It was established and it worked very well, enabling them to put fighter squadrons within visual range (about three kilometres) of enemy aircraft. Also the fighter planes didn’t have to stay up in the air all the time, but could be sent up at the right time and place. This was very effective indeed and, in 1940, ensured victory in the Battle of Britain. Had we lost that battle, we would have lost the war; the Germans would have had complete control of the air.

After the War began, the radar effort expanded dramatically; it became top priority for the Government. Scientists, engineers and others from various disciplines were directed into this gigantic project, which also involved the Army and Navy. Close collaboration with industry and with the armed services was vital for its success.

Were shorter wavelengths developed at the same time?

Yes, they were. It is important to have shorter wavelengths because they enable better directional definition. Work had already started doing that and about 1½ metres had been achieved by the beginning of the war. After the Battle of Britain and the bombing of London during the day, the Germans lost so many planes that they couldn’t carry on with that any more. Fortunately, some far-sighted people had realised, they would then turn to night bombing instead—which they did, with great effect. You could not use the chain stations to deal with night bombing, because it was pointless putting a fighter plane within three kilometres of the target at night, in the dark, because they couldn’t see it. It was essential to develop radar to put on night-fighters so that they could reach night-time visual distance (300 metres) of the enemy aircraft. It was also necessary to develop a new ground-based radar system to place the fighter aircraft within their radar range of a few kilometres.

The breakthrough in the search for an efficient pulsed high- power source of centimetre-waves came in February 1940. Mark Oliphant’s group at Birmingham University invented the cavity magnetron. It was a unique thermionic valve, incorporating crossed electric and magnetic fields and resonant cavities. They achieved a wavelength of 10 cm and a pulse-power of 10kW. This was promptly sent to Bell Laboratory for mass-production (as part of an ongoing military collaboration with the USA). By the end of the War more than a million were produced and a wavelength of about one centimetre and a peak pulse-power of one megawatt had been achieved.

So this had to be something that was light and compact and could go on a plane?

Correct, the invention of the magnetron and development of a 2 kilocycles/sec power generating system led to the birth of air-borne radar. It was small and required little power, so could be installed in the fighter planes. These didn’t have much power available and couldn’t carry much weight.

That wasn’t the end of the radar story, though, was it?

No, an equal danger to Britain, were the U-boat attacks. In the three months from December 1940, one hundred and ninety six ships were sunk without the sinking of a single U-boat. If this had continued, Britain would have been starved into surrender. So they had to develop specialised radar, which could be put on the Sunderland flying boats to enable them to detect the submarines.

They couldn’t detect them under the water?

That’s right; they were underwater all the time during the day. The U-boats (submarines) came to the surface at night, to recharge their batteries and because they could go three times faster on the surface—faster than most merchant ships. So sometimes they could sink up to 30 ships in one merchant convoy.

The early radar was able to detect submarines at night when they were on the surface, but the enemy realised that they were being detected, so they tended to remain underwater. It wasn’t until the advent of ten-centimetre radar, in conjunction with a powerful light on the front of the aircraft, that they could be found and sunk. By the end of 1942 the submarine menace was essentially over.

There was a complete turnaround.

Yes. At the beginning of the war, the British night-bombers were lucky if they got within 50 miles of their target; one pilot commented, ‘Immediately after we took off, we were lost.’ So TRE had to develop devices for precisely determining their location. One of them, a scanning system, was mounted on the bombers. Reflected signals from a rotating 10 centimetre radar beam (shown on a long-persistence cathode-ray tube) enabled a map of the terrain below to be seen by the navigator. This removed any distance limitation because previously, only the closest parts of Germany could be accurately targeted. It was first used, very successfully, on February 1943 for the raid on Hamburg.

The fame of the magnetron did not end with radar. An engineer in the US firm Raytheon (a manufacturer of military radar equipment) noticed one day, when standing near a magnetron tube, that a chocolate bar in his pocket melted. Then he showed the magnetron a bag of popping corn, which exploded all over the floor. Next, he tried a raw egg in the shell! Today, this very same magnetron, operating on 12 cm wavelength, powers the humble microwave-ovens in our homes.

What was your contribution, John, to this work at Malvern?

When I joined TRE, I first went to the training school, headed by Len Huxley, who later became Vice-Chancellor of the ANU. Then I was allocated to the Counter Measures Group. Its function was to counter enemy-radar by jamming, moving to different frequencies, etc. One of the great things that the Counter Measures Group did was to develop a technique called ‘Window’, where half-wavelength-long strips of aluminium foil were dropped from aircraft. These gave much stronger reflections to the German radar than aircraft did and, since there were so many of them, they masked the signals from the planes. This technique was also useful for deception. Just before the invasion of Europe on D Day, planes were sent over the French coast using ‘Window’ to give the impression that there was going to be an attack there when the attack was actually going to be somewhere else.

It’s a very simple jamming device! Looking back, this experience with radar and your own hobbies stood you in good stead with your future research.

It did indeed. I should mention that I worked on high-frequency receivers that scanned a wide range of frequencies to pick up enemy signals. Then, after the war in Europe ended, I was transferred to a group working on missile guidance systems.

Radar had top priority in the UK, involving most scientific brains in the country and significant industrial support. In the US, radar was second in priority only to the Manhattan project; it was essential for them to make an Atomic Bomb before Nazi Germany did. I feel very privileged to have had the opportunity to work on radar during the war. As in any scientific project, it was very exciting and rewarding. I learned a great deal about advanced electronics, pulse-circuitry, etc. This experience and knowledge was of great benefit to me throughout my scientific career.

Radar has had a fantastic impact for many years, not just during the war.

It did, indeed. Our modern enormously complex global air- and marine- transport networks would be impossible to operate without radar. The electronic pulse-circuitry, developed at TRE for radar, was the essential base for the development of computers. Williams and Killburn, from TRE, continued their work at Manchester University and in 1948 set up the very first electronic computer with digital storage, which marked the beginning of the computer age. Radar is even used to detect drivers breaking speed limits!

I hope that you are not breaking the speed limit, John.

I hope not too. An important spin-off from microwave technology in 1954 was the Maser, used today in atomic clocks and measurement of the cosmic background radiation from the Big Bang. Further developments led to the Laser in 1960. Since then this has been used in many human activities such as cutting metal, CD and DVD players, barcode scanners, ophthalmology, etc. Today, ultra high power lasers are being trialled to initiate nuclear fusion for power production. Also the military are working on air-borne lasers to shoot down enemy missiles.

After the war some of the people from TRE went back to their universities and started up radar astronomy. They built radio-telescopes and were able to see objects like quasars, which are the most distant things in the universe, and pulsars, which are neutron stars, with the mass of the sun, rotating around in a few milliseconds. They are cosmic clocks.

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Three Arts Club

What about your social interactions in that period?

I was very fortunate that some of my friends back in Sutton Coldfield, where I lived, had started a club called the ‘Three Arts Club’. This had a very big influence on my life in the future. They were a very nice, intelligent group of people, who used to discuss plays, poems, arts, politics, etc. Also, we had lots of social activities, like playing tennis, going for walks, going to concerts, and cycling trips all over the country. Later on, after the war, we did a lot of hitchhiking trips on the continent, visiting many countries—France, Italy, Switzerland, etc—which was very interesting and educational as well.

It sounds like fun.

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Post-war Cambridge

So you went back to Cambridge in 1946; why was that? Had the place changed?

I returned to take my third year, which was called Part 2 of the Natural Science Tripos. Many of us returning from war activities, which were quite different from studying for examinations, were allowed to take two years over Part 2, rather than the normal one.

Cambridge had changed a lot because the government gave financial support to people, who had been in the armed forces or in research institutions, to go to university. People, like me, returned to complete their degrees, while many others came for the first time. They were mostly not from rich homes and they were much more mature than the normal intake of students who were straight from school. They really changed the nature of Cambridge. Before the war, although it was a great university, it was in some sense something like a rich men’s club, with people mainly from Public Schools. After the war it became a meritocracy, which I think was a very good thing. Also, many of the people in the ‘Three Arts Club’ came up to do their undergraduate degrees. For me, being a shy person, that made things much easier. We enjoyed many social activities like balls, tennis and so on.

So you had lots of fun, John, but what about the physics?

The physics was great. There were some very brilliant people such as Dirac, Devons, Hartree, Hoyle and many others who gave excellent and stimulating lectures. However, one lecturer was so bad that we didn’t even know what he was talking about. It was only after the fourth lecture that I realised he was talking about statistical mechanics. I knew because I had been to Fred Hoyle’s lectures on that subject and I recognised an equation! They certainly stimulated my interest in physics and I ended up with a first­class degree, which I was very happy about. A friend of mine also gained a first-class degree, and we celebrated by blowing soap-bubbles, which floated all over the main court of our College. The first-class degree entitled me to become a research student at Cambridge and also to get a grant from the Department of Scientific and Industrial Research for maintenance.

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A short history of nuclear physics

You joined the Cavendish in 1948, and that was a time when nuclear physics in many ways was still in its infancy.

Indeed, it was. First a little history, in 1911, Rutherford demonstrated with his famous experiment on scattering of alpha-particles by a gold foil that the atom had a very small, dense, positively charged core, which he called the nucleus. He postulated that the central nucleus, which contains nearly all the atom’s mass, is surrounded by a rotating cloud of negatively charged electrons; the electron has a mass of about 1/2000 of the hydrogen atom. His atomic model is similar to the solar system, with the sun containing most of the mass, and the planets revolving around it. The radius of the nucleus is about 10,000 times smaller than the atomic radius of one hundredth millionth of a centimetre! This showed for the first time that the atom was not a solid-like object as previously envisaged.

Yes, it is mostly empty space.

Correct, it is hard to comprehend that a ‘solid’ table is not solid at all. After discovering the nucleus, Rutherford wished to find out its internal structure. He knew from his experiments with radioactivity that very high-energy alpha- and beta-rays must be emitted from the nucleus; also that there must be some very strong short-ranged force to prevent its positively charged components blowing it apart. The lightest nucleus, that of the hydrogen atom, is called the proton. In 1920, Rutherford realised, from a comparison of atomic mass and charge numbers, that all other atomic nuclei must be made up of a mixture of protons and neutrons, particles with similar mass but no electrical charge. In 1932, the neutron was discovered experimentally by Chadwick at the Cavendish Laboratory.

To study nuclei, he had to bang two nuclei together very hard, so that they would stick together or break apart, and observe what happened. For this he required high energy to overcome the repulsive force between the two positive charges. In 1919 he carried out the first artificial nuclear transmutation by bombarding nitrogen with alpha-particles and producing oxygen-17. Little could be learnt because alpha-particles from radioactive sources are not emitted at sufficient rates and they fly off in all directions. Rutherford realised that, because nuclei were so small, the probability of a collision between them was minute.

If they were to collide in sufficient numbers, a very intense, well focussed, ion-beam was required. He thought he could achieve this with an apparatus similar to an enormous cathode-ray tube. It required a hydrogen-ion-source, mounted in a terminal with high positive voltage; the resulting electric field would accelerate the positively charged ions. In 1927, he put his idea to the Royal Society, saying that, with it, we could do things never possible before. He obtained a grant from them and asked two junior colleagues, Walton and Cockcroft, to build such a machine, hopefully reaching several million volts. With great difficulty, due to primitive technology, they successfully completed it by 1932. They managed to get the accelerating voltage up to 200 kilovolts, giving a proton-beam with an energy of 200 kilo electron-volts (keV).

With Rutherford, they bombarded a target of lithium-7 with protons. They observed emission of two alpha-particles (helium nuclei), each with an energy of 8 million electron-volts (MeV). The difference between the initial and final atomic masses showed a deficit of 0.018 units. Rutherford explained that the ‘missing mass’ accounted for the huge liberated energy according to the energy-mass relation, E=mc2 (Einstein 1905). This was the very first proof that Einstein’s equation is correct. A small mass creates huge energy because c2 (the velocity of light, c = 300,000 km/s) is an enormous number. This reaction showed that the atomic nucleus is a vast storehouse of power.

Since then, accelerator technology has advanced with astonishing speed. By the early 1950s, accelerators reached energies high enough to produce new exotic particles. Nuclear Physics’ quest for understanding the building blocks of matter expanded into the entirely new and important field of Particle Physics. At Berkeley, the gigantic Bevatron, producing protons of 6.3 billion electron-volts (GeV), was specifically designed to produce the anti-proton. It was discovered in 1955 followed by the anti-neutron in 1956. Today the world’s largest and most powerful accelerator of 27 kilometres circumference is the Large Hadron-Collider (LHC, CERN, Switzerland). It collides two proton beams, one circling clockwise and the other anticlockwise, each reaching an energy of several TeV (trillion eV). Accelerators have been developed for radiation therapy and for producing radioactive isotopes for medical diagnostics and radiotherapy. Today, proton and carbon beams from cyclotrons are being used to destroy cancers with great precision. Some accelerators provide intense beams of infra-red, to X-rays and γ-rays, to study the structure of materials and molecules. None of these “spin-offs,” technological wonders, were envisaged in the early days of Nuclear Physics.

Just going back to 1948 for a moment, these ideas were around, but not very much was known about nuclear structure or nuclear reactions in detail.

That is exactly right. They knew that the nucleus was composed of neutrons and protons and it was rather like a conglomerate of billiard balls all stuck together. So at that time people often thought that it would behave like a liquid drop, which is rather similar; it has molecules very close to one another that can vibrate collectively together.

Enough was known to actually make nuclear weapons and nuclear reactors because that is about when they started.

That is indeed right. After the discovery of the neutron it was realised that even low-energy neutrons could be used to initiate nuclear reactions, because there was no electrostatic repulsion. In 1938, Hahn and Strassman in Berlin, bombarded uranium with the hope of making heavier elements. Instead, to their surprise, they produced lighter elements such as barium. This finding was interpreted by Lise Meitner and Otto Frisch (Sweden 1939) as the uranium being split by the neutron into two roughly equal ‘fission’- fragments. They thought that the nucleus behaved like a floppy liquid drop, oscillating and eventually splitting. An enormous release of energy (200 MeV) resulted from the Einstein mass-energy equivalence.

Of profound importance was the emission of several neutrons in addition to the fission- fragments. If, on average, more than one neutron is captured by other uranium nuclei, inducing further fission, a chain reaction occurs. This provided the possibility for the development of nuclear reactors and ‘atomic’ bombs. As soon as this was discovered, it all became highly secret and frantic efforts to make a nuclear weapon began in Britain, the USA and in Germany.

Nuclear fission is now a major source of power. As Rutherford’s experiment illustrated, fusion of two light nuclei also produces a vast amount of energy, which may become the power-source of the future.

When I began my research in 1948, there was some puzzling evidence. It was found that nuclei with certain ‘magic’ numbers of nucleons, either neutrons or protons, were especially stable. This was rather similar to the noble gases in atoms. It was the beginning of the study of excited states in nuclei. Nuclei can exist only in certain discrete states of energy, called ‘excited states’. If formed, these states decay down eventually to the lowest state, usually by emitting gamma-rays, which you can study. It was found that, rather than varying smoothly with nucleon number, as you would expect from a liquid-drop model, their energies varied wildly from one nucleus to another. This suggested that the liquid-drop model was inadequate for this purpose.

About two years after I started my research, Maria Mayer developed a rather simple form of independent-particle model, in which the nucleons move more or less independently of one another. Her model explained the magic numbers. It was later developed into the much more powerful Shell Model, which could explain more features; no model can explain all. At this stage, the effects of quantum mechanics, which are vital for understanding nuclear structure, were really not terribly well understood.

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Life at the Cavendish

Who was the Head of the Cavendish at the time?

The Head of the Cavendish was Lawrence Bragg. He got a Nobel Prize for his work on the famous Bragg scattering law for X-rays. He very rarely spoke to research students; I think he felt that they were rather beneath him. But one day we heard a lecture by Cecil Powell, who had sent up photographic plates on a balloon to look at cosmic rays and discovered the pi-meson; it was a very simple experiment, of course. That inspired Bragg so much—because he liked such things—that he actually spoke to me when we were collecting our bicycles from the basement. He said to me, ‘I really think the days of these big machines are over now.’ I wonder what he would think of the Large Hadron Collider?

Who was your PhD supervisor?

At the Cavendish in those days, one had little interaction with one’s supervisor. He would suggest a problem on which to work but after that, a brief talk once a month or so would be the most one could expect. This system was excellent for the best students, fostering initiative and self-reliance, but could be disastrous for weaker students.

My PhD supervisor was Bill Burcham. He was in charge of an accelerator that reached up to about one million volts on its terminal, if you were lucky. This was the accelerator that I used. It was a development of the original Cockcroft-Walton machine. The impressive accelerator-hall had to be very big to minimise the chance of sparking to the walls or ceiling.

Was it open to the room?

Yes it was. Going into the accelerator-hall, when the high voltage was on, was very exciting; your hair literally stood on end. Often you would hear an enormous bang and see a brilliant flash. The accelerator was actually very primitive. Its voltage stability was very poor and the energy of the beam was spread over a range of plus or minus 30 keV. It had a very poor vacuum as well. You have to accelerate the ions in a vacuum; otherwise, they just lose all their energy in the air. The vacuum was full of oil vapour from the un-baffled oil-diffusion pumps. When the beam hit the target—which you hoped was very clean—it cracked the oil-vapour and produced a layer of carbon on it. Sometimes, these layers would get so thick that pieces fell off!

Probably most of the reactions were on the carbon rather than on the target.

Yes, that could be the case.

So the contrast with equipment today or even 20 years ago must have been something dramatic.

Oh, it really was incredible. In those days there were no electronic calculators, no computers, and no transistors. The electronics used valves, which were large and used a lot of power. The equipment was all large and heavy and it wasn’t very reliable. For instance, when we had to count pulses from detectors using a scaler, we usually put three scalers in parallel; if two of them gave the same result, we would assume that was the correct result. This is something that people these days wouldn’t think of. In fact, we had to make most of our electronics anyway, as there were only a few things that we could buy commercially. Most calculations were done with slide-rules and with pen and paper. Another hazard on winter afternoons was that the nominal supply voltage of 210 (50 Hz), would drop as low as 170 volts, making our electronics unusable. We had to raise it back to 210 volts with a manually operated variac. At 5 p.m., when the shops shut, the supply would shoot back up to 210 volts within a few minutes. Failure to quickly wind down the variac would overheat some components, causing damage and malfunction and a strong smell of selenium.

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PhD research – measuring gamma rays

What did you actually work on in terms of the physics?

The accelerator had a low voltage, so we could only study light elements; there wasn’t enough energy to cause reactions in heavier ones. I studied mainly energy- states in light nuclei. Part of my thesis project was to measure gamma-rays in time- coincidence with particles from deuteron-induced reactions and try to learn about the energy levels from which the gamma-rays came. Unfortunately, when you bombard something with deuterons, it doesn’t produce just the reaction that you want; it produces many other reactions as well. So this gives a vast counting rate in your detectors. If you want to successfully measure time- coincidences between the particles and gamma-rays of interest, you really need a very short resolving time. At that time, a resolving time of about one microsecond, possible with available electronics of the radar period, was completely inadequate for this task. So I had to develop equipment that would enable me to produce nanosecond resolving times.

That is 1,000 times shorter.

Yes. Actually, I only managed to get 100 times shorter, but that was good enough; at that time, it was quite an achievement. I had to make instruments and equipment such as amplifiers, double-pulse generators, etc. I also had to make detectors that would produce fast pulses. It’s no use having fast electronics if the pulse from the detector rises very slowly. So I had to make scintillation detectors for both particles and gamma-rays. All this was a big challenge, which took a lot of time, but I succeeded by my own efforts.

And you got some good results?

Yes, I did. I bombarded lithium-6 with deuterons and was able to establish that the first excited state in lithium-7 had a spin or angular momentum of one half. With another proton-induced reaction, I measured the polarisation of the 6.1 MeV gamma-rays from the first excited state of oxygen-16 and showed that it had negative parity. At that time this was the highest energy gamma-ray whose polarisation had been measured, and this remained true for very many years afterwards.

There was also one other thing I did, which was not experimental, and that concerned a theoretical idea about angular correlations. It enabled one to get information from many reactions where, up until that time, you really couldn’t get any information at all. I rather unwisely thought I should do an experiment to demonstrate this theory. This was a very foolish idea, because I was unable to do it at Cambridge. I had hoped to do it at Harwell later, but I couldn’t do it there either, as I needed a helium-3 beam. I couldn’t do it until years later. But in the meantime, in 1961, Litherland and Ferguson published the same idea and got all the credit for it.

Do you think you were not very well advised about the importance of prompt publication?

I wasn’t advised at all but I think I should have had more sense.

So you just gave it away in a seminar somewhere.

Yes, in a seminar at Liverpool University, this was very foolish.

Well, I guess we learn about these things eventually. Who did you work with in the lab?

Apart from part of my first year, when I collaborated with a second year student, I mainly worked alone. There was a very cosmopolitan set of students from many countries at the Cavendish. Amongst them were three Australians: John Carver and Peter Treacy, from the ANU, and Joan Freeman. She was an Australian, but not from the ANU, who remained in England and eventually became Head of the tandem accelerator in Harwell.

Did you complete your thesis at the Cavendish?

I completed my experimental work and wrote part of my thesis at the Cavendish. However the grants were given strictly for three years. I didn’t have any money to stay there any longer, so I had to take a post at Harwell and complete my thesis there.

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Harwell

Harwell is the Atomic Energy Research Establishment?

That’s right. It was located in Harwell, which is near Oxford. I was attracted there because they offered Harwell Fellowships, which enabled you to do whatever work you were interested in with the facilities that they had. Their facilities were very good. I was interviewed by a committee headed by Sir John Cockcroft, who was the Director.

His name keeps popping up.

Yes, he was a remarkable man with a fantastic memory. Although there were 3,000 employees in Harwell, I would meet him sometimes walking around the establishment and he always knew who I was and addressed me by my name. Sometimes he would come into the lab and talk to people about their research; he always seemed to be well up in what they were doing. He was an unusual man and a great director. Harwell was never the same after he left.

I went to the nuclear physics division, which was headed by Egon Bretscher, who had worked on the atomic bomb project in the US during the war. I got on with him very well, but he was quite an eccentric person. If he didn’t agree with some proposal, he delighted in an endless conversation of irrelevancies. My group leader often used to come out of these meetings with a white face and trembling.

A diversionary tactic. At Harwell, as well as experimentalists, you worked with some theoreticians?

Yes there was an excellent theoretical physics group there. It interacted strongly with the experimentalists. I started my research together with Basil Rose, who was a very good experimentalist, and I learned a lot from him. We worked on gamma-rays from radioactive nuclei. At Harwell it was possible to get such sources rather easily, either produced in the local nuclear reactors or sometimes in atomic bomb tests. Also, at that time we had some outstanding detectors; they were proportional counters filled with xenon or krypton, which had very good energy-resolution. To do these experiments, you really needed good energy resolution. For instance, if you wish to measure two gamma-rays close to one another in energy, you can distinguish them if the width of the peaks from the detector are less than the energy-spacing (good resolution), but not otherwise. So good resolution was essential for these measurements, and enabled us to achieve excellent results.

At that time there were some new theoretical developments. The old Shell-Model had been very much refined as a new model from Bohr and Mottelson came along. This indicated that not all nuclei were spherical, as previously thought, but could be deformed into rugby-ball shapes; they could exhibit collective motions, like vibrations or rotations. This was a very exciting theory at the time. So our experiments were directed at trying to see whether this theory was correct. We found that the nuclei uranium-234 and -238, and plutonium-239, behaved almost as perfect rotors, in agreement with the Bohr and Mottelson theory.

So you developed a better understanding of heavy nuclei.

I did. Particularly because, in 1952, Otto Frisch came to Harwell and asked me to write a review article for ‘Progress in Nuclear Physics’ on the topic of ‘the nuclear properties of the very heavy elements’. This greatly broadened my knowledge and understanding of this subject. In doing so, I noticed two aspects that had not been explained at all before. One was related to the spontaneous fission of odd-mass nuclei. Spontaneous fission occurs when a heavy nucleus, such as uranium-235, splits up into two by itself.

Without hitting it with a neutron?

Yes; no neutrons at all. The other one related to the alpha-decay of heavy odd-mass nuclei compared with doubly-even nuclei. I was able to provide two simple but basically correct explanations for both these phenomena and I published them in the review article.

But you didn’t get the credit for the ideas.

No. Unfortunately I never seemed to learn from my mistakes. I should have published it in a regular journal first.

But there were other discoveries to do with the excitation of heavy nuclei that would have a profound effect on your career.

In Copenhagen they discovered a new type of nuclear reaction. Previously, people thought that the two nuclei had to hit one another before any excitation could occur. But it turns out that, if they don’t actually hit but come fairly close, the time-varying electric field from the projectile can excite states in the target nucleus, or vice versa. This is called Coulomb excitation. It turned out to be a very valuable tool because not only does it excite the states but also you can learn various things about them, such as the strength of the gamma- ray transitions and so on.

By this time the original high-resolution proportional counters had been developed into high-pressure proportional counters, which had a much larger efficiency of detection and still gave very good resolution. It occurred to me that I could use these to study the Coulomb excitation of very heavy nuclei. This was very difficult to do, because the targets were radioactive, producing gamma-rays of their own, the gamma-rays of interest were very weak because of high internal conversion, and because a continuous background of gamma-rays was always generated. Anyway, I was successful in making the first observations of the gamma-rays from these nuclei. From the theory of Bohr and Mottelson I was also able to deduce, for the first time, the amounts of deformation of the rugby-ball shapes.

Stan Thompson, from the Lawrence Berkeley Laboratory (LBL) came to visit Harwell for a two days and I showed him around the establishment. He must have thought I would be a suitable person to go to their lab and start up a new field of Coulomb excitation. They were starting to build a new Heavy-Ion Linear Accelerator (HILAC). Such an accelerator is excellent for Coulomb excitation because the nucleus of a heavy ion has a very large electrical charge, giving a much bigger probability for exciting a target nucleus. So, after he had gone back, Bretscher got a letter from Glen Seaborg, who was the Head of the Nuclear Chemistry Division at LBL, saying that they wished to establish an exchange scheme with Harwell and that I would be the first person to be exchanged. He asked whether Bretscher would agree to this and he kindly did so. I was the first person to be exchanged—and the last one, as far as I’m aware.

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Exciting new world – San Francisco, California

That was an important move in your career. You went to the US and specifically to San Francisco in 1956. The United States and Berkeley itself must have been quite a contrast to what you were used to in your life in England.

Yes it was, especially as England had still not fully recovered from the war. We sailed on a ship, the Orcades, which went through the Panama Canal. We went economy class; the food was excellent and the company great, so we had a wonderful time on the ship. We went through the US immigration formalities on the ship. These were rather curious. They asked questions such as, ‘Are you intending to enter the United States for the purpose of overthrowing the government of the United States by force?’ Another one was, ‘Are you entering the United States for the purpose of indulging in organised vice and prostitution?’

I think they are still asking the same sorts of questions.

Maybe they do; but I thought they were rather strange. When we got near to San Francisco, the coast looked very wild and desolate. Then suddenly we came to the entrance to the San Francisco Bay Area and went under the Golden Gate Bridge. There was an amazing view of all the skyscrapers in San Francisco, the enormous Bay Bridge, Alcatraz Island—where they kept violent criminals—and lots of cities across San Francisco Bay. It was a beautiful sunny morning, and was a wonderful beginning to our stay in the United States.

We were met at the dock by John Rasmussen and Stan Thompson, from the lab, and taken to a motel for the first night. That, in itself, was quite an experience because at that time there weren’t any motels in England; I had never seen one before. So we slept overnight and came down in the morning to breakfast. There, a very nicely dressed young lady came to wait on us. From my accent, she realised that I wasn’t American and asked, ‘Where did you come from?’ I said, ‘I came from England,’ and she then asked, ‘Do they speak English in England?’ Then she asked ‘Which way did you come here?’ and I said, ‘I came by ship through the Panama Canal.’ She then asked, ‘Did you have trouble getting through?’—and that again was surprising. At that time the Suez Canal was closed and she didn’t realise that the Panama Canal was then a US possession.

She probably thought that the Suez Canal and the Panama Canal were the same canal!

The US was quite amazing after Britain. We went into supermarkets, where there were enormous arrays of fantastically beautiful-looking food. If you went to a restaurant, they gave you meals that were sufficient for three people. I remember on one occasion that I saw a notice saying, ‘Breakfast served all day: 2½-pound (1.14 kg) steaks’. That’s changed a lot now.

The lab itself was very impressive and it had very good facilities. I was welcomed with open arms. It was so good to be addressed as ‘John’ rather than ‘Dr Newton’, as I was in England. Class distinction in England is appalling and humiliating. In Manchester University we had two separate tea rooms, one for technical and another for academic staff; neither would ever venture into the tea room of the other. Rutherford, one of the greatest scientists of all time, a bluff New Zealander, disliked snobbery and the Class System to which he became a tragic victim. In 1937 he developed a strangulated hernia, requiring urgent intervention. Because he had been made a Lord, only a surgeon of equal rank could operate on him. By the time a ‘noble surgeon’ was located and brought in, it was too late.

Seaborg was the Head of the laboratory. He was a Nobel Prize winner; he got his prize for discovering plutonium. He ran the lab very well indeed. Every lunchtime the senior staff, myself included, used to take sandwiches to his office. Here we would talk about everything that was going on in the lab and sometimes about American football, which was one of his favourite topics. This was excellent for fostering unity in the lab and for keeping everyone informed.

I shared an office with Sven Gosta Nilsson, a famous theorist, who came from Sweden. He developed the independent-particle model for deformed nuclei, which has been used extensively ever since. We became very good friends with him and his wife. He was a very informal chap, but his Swedish origins showed up very occasionally. On leaving his house and saying good bye, he would suddenly stiffen up, click his heels, put his hands out and said good bye. He was a wonderful person.

He was one of the many talented visitors at Berkeley.

Yes. Many visitors came to the lab, people like Bohr and Mottelson—very high-level scientists. There was an excellent theory group there, which interacted a lot with the experimentalists. It was a very beneficial arrangement altogether.

Just to talk a bit more about Berkeley, John, did you actually use the HILAC?

I did, but not for a year, because it wasn’t completed until then. In the meantime I had to do something else. I investigated the energy levels of some rhenium nuclei, produced in the decay of radioactive osmium. They were on the border of a deformed region of nuclei. The osmium was produced by bombarding tungsten in a cyclotron. They brought up this intensely radioactive piece of tungsten and I had to separate out the minute amount of osmium from it. So I had my first and only venture into radiation chemistry, eventually plating the osmium on to a thin platinum wire. This experiment was successful. I was able to show that these rhenium nuclei were deformed. I also learned something about the Auger electrons emitted in transitions between atomic excited states. So, after I had done all that, I eventually came to the HILAC.

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Double Coulomb excitation

Was the HILAC a good machine when they got it going?

It wasn’t very good for what I wanted to do. It only produced two energies, 10 MeV and 1 MeV per nucleon. It didn’t give a continuous beam, like the accelerators I had worked with before. Instead it consisted of two millisecond pulses every 100 milliseconds. So 98 per cent of the time there wasn’t any beam. This meant that you couldn’t do coincidence experiments with it.

For Coulomb excitation, the required energies were less than 5 but not as low as 1 MeV per nucleon. Frank Stephens, a very bright person, who had just completed his PhD in Berkeley, was chosen to work with me on this project. We had a hard time in the beginning. One challenge was that the accelerator produced vast amounts of high-energy gamma-radiation all over the lab, including the counting areas, and a lot of high-frequency radio-radiation too. They were not used to doing online experiments there, so it was very difficult to persuade them to put in concrete shielding and a gamma-ray cave so that we could actually do some experiments.

Eventually we succeeded and I decided that it would be interesting to look at double Coulomb excitation; that’s when you Coulomb excite from the lowest state to the first excited state and then up to the second. This had never been observed before. In order to achieve the energies we wanted for this experiment, we passed the 10 MeV per nucleon beam through a tube full of hydrogen gas. This reduced the energy, which could be varied by changing the pressure of the gas. This spread the beam so the target had to be very large, because there were no focusing arrangements. Anyway, we were successful in doing this experiment and the results appeared in the first issue of Physical Review Letters.

Physical Review Letters is now the major journal in physics.

Yes, it is. After the double Coulomb excitation but only a few days before I had to go back to Harwell—Harwell had already been very kind in giving me an extra six months—I did some preliminary experiments trying to look at projectile-Coulomb-excitation. Coulomb excitation is more effective the larger the electrical charge you have on the exciting nucleus. So, if you bombard a very heavy target nucleus, which has a big charge, with a projectile, you can excite the projectile with a high probability. I did a couple of preliminary experiments and managed to see projectile excitation in aluminium-27 and neon-20. But unfortunately I couldn’t complete these measurements, because I had to return to Harwell.

Although you didn’t get a chance to use these things, John, multiple Coulomb excitation has become a powerful and very important tool in spectroscopy, as has projectile excitation. You didn’t get the chance to use it yourself, but they became a key part of later work by other people at Manchester and eventually in Canberra.

That’s absolutely right. I was rather sorry that I couldn’t pursue it further.

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Manchester

When did you join Manchester?

In 1959 - Sam Devons had come to Berkeley on a visit and he asked me to apply for a senior lectureship there. I was rather attracted by this, partly because Sam himself was such a brilliant man—I think he was the most brilliant nuclear physicist in England after the war—and partly because he already had a six million volt accelerator there and had the money to build a new heavy-ion linear accelerator, similar to the one at Berkeley. So I went to Manchester. Unfortunately for me Sam Devons left after about a year and went to Columbia University in New York.

This post was not solely for pure research, as at Harwell and Berkeley, but also involved a lot of teaching, which was taken very seriously in Manchester. I had to give lectures, tutorials, practical classes, attend ‘Steering Committees’ and so on, which took a lot of time away from the research.

In 1961, we held an International Nuclear Physics Conference to celebrate the 50th anniversary of Rutherford’s discovery of the nucleus. Many of the pioneers of nuclear physics, like Niels Bohr, Lise Meitner, Walton etc, came to this historical event. They participated in a special session. I took Lise Meitner to her hotel and found her a most charming lady. At the end of the Conference, delegates were treated to a special concert by the Hallé Orchestra conducted by Sir John Barbirolli. I was on the Organising Committee then, and now, 50 years on, you, George are on the Organising Committee of the 100th anniversary conference, honouring Rutherford, to be held next year, again in Manchester.

Next year, yes. What was the direction of your research work at Manchester?

Initially I used the six-megavolt machine and I carried out the experiment to verify the theoretical idea in my PhD thesis, which I had hoped to do for many years; of course, it was much too late. Then I spent a lot of time with the new HILAC. As at Berkeley, there were lots of problems with vast amounts of gamma- and radiofrequency-radiation, all over the lab. I was involved in solving these problems, setting up the beam lines and so on.

In 1963 a new type of reaction was discovered by Morinaga and Gugelot. It was the fusion-evaporation reaction. In this, two heavy ions fuse together forming a ‘hot’, highly excited, compound nucleus. It loses its energy, first by evaporating several neutrons, similar to molecules from a hot liquid, and then, when there is not enough energy to emit further neutrons, it evaporates gamma-rays—they have so many different energies that you can’t distinguish one from another—and they form a continuum. Then, when the nuclear energy becomes low enough, one sees individual discrete gamma-rays coming from the decay of low-lying excited states.

I became interested in these reactions, which, for several decades, offered the most powerful method for studying excited states through measurement of the discrete gamma-rays. To study these you need a detector with good energy resolution, so that you can distinguish one gamma ray from another. There are two types of detectors which are suitable for this. One is the germanium detector, and the other a magnetic spectrometer. We didn’t have any germanium detectors at the time, so I got David Ward, who was a very bright and enthusiastic student, to make a single-gap wedge spectrometer and we used this as a tool to do a number of experiments with our HILAC.

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Berkeley revisited

You were divorced in 1961, John, and remarried in 1964 and, not long after that, you went back to Berkeley for an extended visit. Was that a productive time?

The divorce was a most traumatic event, losing my three children to the United States. The visit to Berkeley was still very productive. The Berkeley lab had changed a lot since my last visit. There was now the 88-inch heavy-ion cyclotron, which was an excellent accelerator, as well as the HILAC. The HILAC had been upgraded, with its duty-cycle increased from two per cent to between 20 and 50 per cent. It consumed as much power as the whole City of Berkeley; they had to pour water over it to keep it cool!

Seaborg had left to become head of the Atomic Energy Commission, so there were no more lunchtime meetings. Isadore Perlman was his successor. He was a very bright and intelligent man and very modest. Once I was walking around the corridor with him, when one of the cleaners came up to Perlman and said, ‘Say, I haven’t seen you before; what’s your name?’ Perlman told him what it was and walked on quite unconcerned. To have that happen in the United Kingdom would be unimaginable.

Yes; he would get the sack.

He would indeed.

Had the lab changed since the previous time?

Yes, the lab had changed because of the new facilities. Frank Stephens and Dick Diamond had set up a very good group. Some of my old students came during my visit, David Ward and Jack Leigh. The facilities were far better than in Manchester, so one could really do great research.

I first became involved in a systematic study of angular distributions in heavy-ion fusion- evaporation reactions. We found a simple explanation for our results, which was very useful for future measurements. We made the first experiments with very heavy argon-40 projectiles, and compared the population of discrete gamma rays with those from lighter projectiles. This gave us a much better understanding of these reactions.

You were offered a chance to stay in Berkeley and you declined and returned to Manchester. Was that a decision you regret in retrospect?

Yes, I did regret it because my forte was more in doing research than in undergraduate teaching. Also, the facilities at Berkeley were much better than anywhere else in the world. It was the centre to which people from many countries came to work. So possibly I made a mistake in not accepting that.

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Setting up an accelerator in Canberra

It wasn’t long after that before you moved again, with the prospects of new facilities and opportunities for full-time research being the attractions, when Sir Ernest Titterton invited you to apply for a position at the Australian National University.

Yes. Ernest Titterton came to Manchester and asked me to apply for the position of Head of the Department of Nuclear Physics at the ANU and he told me that he had $2.2 million to buy a new tandem-accelerator. This was very attractive because I had got thoroughly fed up in the UK. All the UK accelerators were outdated. We had been talking for years and years about getting a big new tandem accelerator, but discussion was still going on and much of the discussion was, ‘Should we put it in Oxford or should we put it in the North of England or somewhere else?’ I was very tired of this, so the attraction of having the $2.2 million to get a new one was quite appealing. Actually, it was 13 years before the new UK accelerator finally started to work.

Actually, I went to Manchester in late-1970, not long after you’d been there, and they were still discussing where to put such an accelerator, and I was involved in the committee to do with that. When did you actually come to Canberra then?

We arrived in February 1970, travelling on the liner Canberra, a nice ship—

Very appropriate.

Yes indeed—which went via South Africa. When we got to Sydney Harbour, it was a remarkable and impressive spectacle. Ernest Titterton met us at the dock and drove us back to Canberra. I was surprised that the outskirts of Sydney reminded me of Manchester. That summer was unusually wet, so all the fields were green, which was very uncommon in February. But in spite of this it didn’t look anything like the UK, so I could see that Australia was very different. Ernest had set up a very thriving laboratory that had a 6 MV tandem accelerator, which worked very well, and a good group of people. He was a very far-sighted and entrepreneurial person, which had been of great benefit in the past.

Were you involved in the development of the new facilities at the ANU?

Yes, I was. First of all, we had to decide on what sort of tandem accelerator we were going to get—

How to spend the money?

Correct—and we were able to get a very much better accelerator than originally anticipated. It was a vertical 14 megavolt terminal tandem accelerator (14 UD), built by the National Electrostatic Corporation (NEC), and with an entirely new and original design. I guess it was a bit of a risk taking it on, but it turned out to be very successful. NEC was to build the accelerator and then, in Australia, we had to build the pressure- vessel to contain the accelerator, the support system for this—which had to be very carefully positioned—the beam lines, vacuum systems and so on. So there was a lot of work for us to do; it wasn’t just buying something off the shelf.

At the time the Australian dollar had reached a remarkable value of US$1.4. So we had some money left over from this project. We bought a cyclotron that could inject negative ions into the six megavolt tandem and make it a more powerful machine with much higher energies. This proved to be very useful and I and many others worked with it, long before the 14 UD came into operation.

The period from 1970 to 1980 was one that saw a significant change in both the style and the program of research in the nuclear physics department that you were now the head of.

It was indeed. My primary objective was to initiate research in heavy-ion reactions, which had not been done previously in this lab. I also wanted to encourage people to work in larger groups. The tradition in Canberra—and in many other places—was that you had one staff member with, say, a couple of research students working on one project and other staff working on other projects, with little interaction between them.

Working in larger groups facilitates mutual interaction; it is stimulating and generates new ideas. With rapidly advancing technology, by 1970, the experiments and equipment had become much more complex and the amount of data to be analysed immensely greater. It was therefore becoming essential for people to work in a group. When I was a research student, we made everything ourselves; we did the experiments ourselves and didn’t discuss much with anyone else.

Also I had the ambition to make the lab more democratic. Ernest Titterton had been a very authoritarian leader and I felt a lot of people in the lab had resented it. I hoped to make the atmosphere a bit better.

A major success in your own research using the new accelerator, when it came on line in about 1975, was the first characterisation of continuum gamma rays in heavy-ion xn reactions, a subject that you had had a long­term interest in.

Yes –and the 14 UD gave me my first opportunity to do something that I wanted to do. It was actually the first observation of a particular type of continuum gamma-ray and it started an entirely new field of research. The work was published in Physical Review Letters and apparently caused a lot of consternation and distress in Berkeley, because they were hoping to do something similar.

I think it was called ‘Black Friday’ when they received the publication.

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Drawn back to Berkeley

When things settled down in the research program, John, you embarked on another visit to Berkeley, a favourite place of yours, but also you produced some important results.

I liked LBL because I very much enjoyed working with Frank and Dick and with the fantastic facilities there; I liked the environment in Berkeley too. When I got there, both Frank and Bentt Herskind, who was a visitor from Copenhagen, were interested in continuum gamma-rays, as was I. We were all concerned with the possible effect the giant dipole-resonance might have on them. The giant dipole-resonance is a collective vibration of the neutrons against the protons. It’s a peculiar sort of resonance, but an important one. We designed an experiment to do this. It was a difficult experiment to carry out, but we were successful in the end. My previous research in Canberra enabled me to provide much of the theoretical input for interpretation of the results. This started an entirely new field of research into continuum gamma rays—completely different from the previous one.

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A change of field

You came back to Canberra in 1982 and that corresponded again to another change in your research, still using heavy ions but now heavy-ion fusion.

That’s right. This line of research was in contrast to my previous work, which was concerned mainly with the independent-particle aspects of nuclei. This was concerned more with the collective aspects, such as in nuclear fission. I looked at previous studies in this area and found them to be very unsystematic and fragmentary; they really didn’t lead to any new physics. I felt that we could do much better. With Jack Leigh and some very capable students, one of whom was David Hinde, we succeeded in doing so.

One of the interesting results from this research was that, not only was collective motion involved in nuclear fission, but energy dissipation (viscosity) as well. This hadn’t previously been realised and it changed the nature of the subject. Fusion occurs when two nuclei fuse together. To understand the fission process it is necessary to understand fusion as well. If two nuclei move towards one another, they repel each other until they come close enough for the nuclear force to overwhelm the Coulomb force. The energy required to bring them together to that point is called ‘Coulomb-barrier energy’. It was previously thought that there was just one single Coulomb barrier. However, a new theory by Rowley and Satchler proposed that there wasn’t just one barrier but a distribution of barriers. This distribution depended on the independent-particle structures of the colliding nuclei and their shapes.

Jack Leigh led the group to try to verify this and possibly use it as a tool. He made a unique velocity-filter that enabled us to do this successfully. The 14 UD accelerator itself was essential to the success of these measurements; it has remarkable flexibility, stability and reproducibility. Much of the credit for this goes to David Weisser and to Trevor Ophel, who continually improved it since its acceptance in 1974.

An important factor in these measurements, as you say, is the flexibility of the accelerator, but they are also very precise measurements.

Yes, we needed about 10 times better precision than had previously been achieved, so the measurements were very difficult, but we succeeded. A lot of insights into fusion itself flowed from this work, in addition to helping an understanding of fission.

The group involved in this work, initially led by Jack Leigh but now led by David Hinde and Nanda Dasgupta, is the undisputed leader internationally. Many labs around the world have tried to emulate the work but probably not so successfully. This must be a source of some satisfaction to you.

Yes indeed - I think they’ve done a fantastic job and they’ve developed some excellent equipment and outstanding ideas to study this subject.

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Concerns for the future

On a more general question, John, in recent times you’ve been concerned about issues broader than the ones that fascinated you about nuclear properties over many years—population, consumption and sustainability. Do you want to say something about this sort of thing?

Thank you George for this question.

Science is exciting and rewarding because it extends the horizons of our basic knowledge and it drives technology that leads to prosperity. Knowledge is now growing faster that ever before, far beyond the capacity of most people to comprehend it. However, the information concerning the threat to our civilisation should be presented clearly, objectively and without any prejudice, to the wide community.

I have been concerned about our global future for very many years. I spend a lot of time researching and thinking about the challenges of climate change, resource depletion and environmental destruction. I have given a number of talks and written articles addressing objectively these issues. For the last 200 years, human population and consumption has increased roughly exponentially. Politicians, businesses, banks, economists, etc, want this to go on forever. Governments are terrified by anything that threatens growth and now are pouring billions of public money into a failing financial system. Even a growth rate of 4% per annum, doubles growth in 18 years. Exponential growth depends on numbers. It is slow for small numbers but rises dramatically with increasing numbers.

An example is the fable of the Persian King, who agreed to pay for a beautiful chessboard in “rice currency”. The price was one grain of rice for the first square, two for the second, four for the third, and so on, doubling up for each square. The 10th square took 512 grains, the 15th 16,384, the 20th over half a million and the 46th 35 million-million grains (35,000 tonnes). The 64th square required 10 trillion tonnes of rice, far beyond the present global annual output of 450 million tonnes! The crunch strikes surprisingly suddenly.

Our planet is finite (limited) and continued growth, let alone exponential, is not possible; it would end in disaster. We are living unsustainably from nature’s capital, which is rapidly being depleted. To support present global consumption of food, water, resources and energy requires 1.4 Earths, far beyond the planet’s carrying capacity. We are exploiting the Earth’s life-support-base to exhaustion, at our peril. Phosphates are mined recklessly (for fertilizer) and rock deposits will be used up within 100 years. Phosphorous is essential for all life (DNA). Rainforests, the richest sources of biodiversity and climate stabilisers, are being ruthlessly destroyed. Pollination by bees contributes about 30% to world food production and bee colonies are collapsing worldwide. With the present global population of 7 billion, increasing by 9000 an hour, 80 million a year, current living standards cannot be maintained.

Rich countries must stop their gross over-consumption and waste of resources, energy and meat, whilst billions live in abject poverty. To produce one 1kg of beef requires 200 times more water (a scarce commodity) than 1 kg of wheat. Worldwide, livestock emit 18% of greenhouse gases, more than all forms of transport combined. We have to change our attitude to life, accepting a radical reduction in material living standards, a more equitable distribution of wealth and an eventual substantial reduction in population. We can’t wait for Governments to take the lead. We must make the change for our children’s children. If we fail to act now, James Lovelock might well be right that, by the end of the century, 80% of the human race will be wiped out.

That is probably a negative note to finish on, John, but I think we can be optimistic. It does, though, need a large change in the way that we think about our lives and our thoughts about the future. Getting people to reduce their consumption is something that has rarely happened in the past and really it is a serious challenge for society.

Thank you, John, for telling us about your life and your very long scientific career. Let me wish you good health and good luck in the future.

Thank you very much, George, for all the effort that you’ve put into this and in making it a very happy occasion.

It’s been a pleasure.

[The invaluable assistance of the Project Officer Dr Cecily Oakley is greatly appreciated by Professor John Newton.]

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© 2017 Australian Academy of Science

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