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Now in his 92nd year, Mark Oliphant is wearing well. His legs may no
longer carry him with certainty; his hearing, impaired since childhood,
may demand that conversations be carried on at above normal volume. But
he still stands tall. His ruddy face still routinely creases with mirth,
aided by the booming laugh that has been his trademark for so long.

It is his mind that remains most active. Currently he is an evangelist
for ‘hydrogen power’ – the use of hydrogen, released from water by electrolysis
or some other process, as a fuel for vehicles or to power the innovative
high-temperature fuel cells being developed in Australia. The electricity
needed, he says, may well come from sunlight, captured by the high-efficiency
solar cells developed by Martin Green at the University of New South Wales.
Oliphant freely acknowledges the problems that remain, such as storage.
Yet he feels able to say with conviction: ‘I am confident that such a system
for producing power from hydrogen, the cleanest of fuels, will prove itself
early in the next century’.

His interest in hydrogen as a source of power is highly appropriate.
His early scientific reputation was built on hydrogen or, to be precise,
on pioneering researches he undertook into nuclear reactions involving
deuterium, a heavy istotope of hydrogen. There is a key difference, of
course. Today, Oliphant sees hydrogen as a source of chemical energy, liberated
when hydrogen is burnt in an engine or a fuel cell. Such an energy source
is within our grasp, with just some small matters of technology or economics
to be tidied up. In the 1930s, the promise was something much more profound
and much less accessible – energy from within the nuclei of hydrogen atoms.

The story begins in 1932 at the Cavendish Laboratory of the University
of Cambridge. The Cavendish was then at the height of its influence. Ernest
Rutherford, the New Zealand born physicist who had almost single-handedly
created the science of nuclear physics, had built a team of researchers
who led studies of the world within the atom. Some measure of the intellectual
resources of the Cavendish comes from the annual photograph taken in 1932.
Of the 30 or so staff and students gazing solemnly at the camera, nine were
already, or were to become, winners of Nobel prizes. Oliphant stands in
the second row of the group, fourth from the left and a but note quite behind
Rutherford. It is a symbolic position. Oliphant was not yet in the front
rank of the Cavendish, but he was not far behind.

By the start of 1932, he had been at the Cavendish a little over four
years. He had his doctorate and his first research papers in print. He was
also growing close to Rutherford, professionally and personally. They were
both antipodeans, given to plain talking. Oliphant and his wife Rosa were
often guests of Ernest and Mary Rutherford at their holiday cottage in the
north of Wales. And Rutherford appreciated Oliphant’s growing reputation
as a designer, builder and operator of the complex apparatus on which progress
in nuclear physics was increasingly depending.

THE WONDERFUL YEAR

Arguably, 1932 was the year of greatest achievement at the Cavendish
with three discoveries of such importance that they truly deserve the overworked
accolade ‘breakthrough’. For the previous two decades, the standard model
of the atom had contained two types of particles: the light, negatively
charged electrons and lumps of positively charged matter called protons.
Then in the space of a few months, the number of known fundamental particles
doubled from two to four; the atoms of the lighter elements, far from being
indivisible, were broken open at will; and powerful new machinery for both
producing and detecting the particles came into use. These discoveries gave
nuclear physics a new impulse. And the four men most closely involved at
the Cavendish became Nobel laureates.

First to shine was James Chadwick, Rutherford’s greatly respected second-in-command.
At the beginning of 1932, he followed up an old idea of Rutherford’s and
some recent discoveries in France and Germany, and with brilliant insight
identified a third fundamental particle – the neutron, close to the proton
in mass but with no electrical charge.

John Cockcroft and Ernest Walton came next when, in April, they ‘split
the atom’. They had built one of the first particle accelerators, a sort
of gun which used electrical potentials of several hundred thousand volts
to send protons (the nuclei of hydrogen) speeding down an evacuated tube
to collide with targets made of light elements such as boron and lithium.
A multitude of tiny flashes on a screen covered with zinc sulphide revealed
that, under proton bombardment, such light elements disintegrated into alpha
particles, the nuclei of helium atoms.

Patrick Blackett completed the run of successes in August when he developed
an improved version of the cloud chamber (another Cavendish invention) into
a powerful research tool for revealing the paths of the particles in cosmic
rays. With this, he trapped evidence of a new form of matter. This was the
positron, identical to the electron except that it was positively charged;
it was the first evidence of ‘antimatter’.

Oliphant was only a spectator of these triumphs. His own research interests
lay elsewhere. That was soon to change. Shortly after Cockcroft and Walton
split the atom, the Rutherfords invited the Oliphants to their Welsh retreat.
Conversation turned quickly to the recent breakthrough. Rutherford had never
been overly keen on large and complex apparatus, fearful that building and
running such machines might take precedence over what really mattered, the
collection of experimental data. Yet he saw that times were changing, and
proposed a joint project that would explore where Cockcroft and Walton’s
work was pointing. The first task was to design and build an accelerator
of the Cockcroft-Walton type, but with some new features.

ROOM WITH A PAST

Oliphant went to work in the summer of 1932 in a couple of low-ceilinged,
stone-flagged rooms in a historic precinct of the Cavendish basement. In
one of the rooms, Lord Rayleigh, an early director of the Cavendish, had
made the first precise measurements of the value of the ohm, the unit of
electrical resistance. In the same room, Rutherford and Chadwick all but
achieved the dream of the alchemists in 1919 when they transmuted matter
for the first time, turning atoms of oxygen into nitrogen.

Oliphant’s accelerator was as similar to Cockcroft and Walton’s as a
machine gun is to a cannon. Their accelerator produced a beam of very powerful
protons, carrying up to 600 000 electronvolts of energy. Oliphant’s machine
yielded protons carrying at most 200 000 electronvolts, but delivered a
hundred times as many protons to the target, so greatly increasing the
chances of a nuclear reaction taking place. With counting chambers and electronic
amplifiers replacing the eye and the sulphide screen, debris flying from
the point of impact could be measured more precisely.

Rutherford was very busy, with a laboratory to run and commitments that
regularly took him out of town. This meant he kept his colleague on a very
long leash, though the great man would drop in on Oliphant and his co-workers
once or twice a day, if he could, to see how things were going. He was intensely
interested in progress, and his brilliant insights and explanations of observations
were beyond price. But Oliphant really ran the show. His name was to come
first on the half-dozen scientific papers hewn from the mountain of data
yielded by the basement accelerator. Rutherford’s name came last, if it
appeared at all.

For the first few months, Oliphant and Rutherford used beams of protons
to break open the nuclei of lithium, boron and beryllium, as Cockcroft and
Walton had done, though with greater precision. By so doing they cleaned
up many of the small uncertainties and turned out a paper or two.

The project took a leap forward in the summer of 1933, with a visit
by Gilbert Lewis, a chemist from the University of California at Berkeley.
Lewis had a present for Rutherford, a few drops of the newly isolated ‘heavy
water’. In this precious liquid, the hydrogen in many of the water molecules
had been replaced by ‘heavy hydrogen’, twice as heavy as the more common
form. Although the Americans had already named the new form of hydrogen
‘deuterium’, and its nucleus ‘deuton’ (now changed to deuteron), Rutherford
obstinately insisted on calling the atom ‘diplogen’ and the nucleus ‘diplon’.
In the wake of Chadwick’s discovery of the previous year, it was clear that
each diplon contained a proton and a neutron. The diplons made most effective
bullets for the Oliphant gun, producing many more transmutations than the
single proton of a hydrogen nucleus.

Soon, however, confusion set in. Oliphant tried a number of elements
as targets, but the results all looked much the same. The debris clattering
into the counting chamber was almost always dominated by protons with a
constant energy – enough to travel 14 centimetres in air before coming to
rest. There was some evidence that neutrons were present, although these
were difficult to detect. Similar work was going on in Berkeley, led by
Ernest Lawrence, then a rising star in nuclear physics. The Berkeley researchers
had an explanation – the deuton (sticking to their nomenclature) was an
unstable particle which on impact with the target shattered into a proton
and a neutron.

STICKING TO THE TARGET

Not so, said Oliphant. He suspected that the answer lay with contamination
of the target, because he had observed that the number of protons increased
with time. If the diplons fired from the beam somehow stuck to the target,
they would themselves become targets for more diplons coming behind. Oliphant
(and Cockcroft, who was loading his accelerator with the same stuff), already
knew that cleaning an exposed target greatly reduced the number of protons.

To settle the matter (and the well-mannered argument between Cambridge
and Berkeley), Oliphant had a colleague make targets from ammonium sulphate
and phosphoric acid, replacing some of the hydrogen in these compounds with
heavy hydrogen. There was no doubt about the result. The characteristic
pattern of protons appeared at once. Clearly the real collisions were between
diplons, rather than between diplons and the original target material. Lawrence
was quick to agree, with good grace, that Oliphant had been right.

The clash of the diplons still posed some puzzles. The matter become
even more complex when Oliphant went hunting for any other particles that
might be produced by the impact of diplon on diplon. His detection apparatus
included a sheet of mica to determine the energy of particles leaving the
site of collisions. These were of different thicknesses, to represent the
stopping power of various thicknesses of air. With the help of Rutherford’s
technical assistant George Crowe, Oliphant split a sheet of mica so thin
that it showed dazzling interference colours. With that ultrathin film,
they were able to observe a second group of particles, roughly equal in
number to the protons, which only had enough energy to travel 1.6 centimetres
through the air before coming to rest. These particles carried a single
charge, and so were still hydrogen nuclei. But their tiny range indicated
they must be heavy: the mass/energy calculations showed that they weighed
three times as much as ordinary hydrogen. It could only be a hydrogen particle
of mass 3.

The basement accelerator had delivered its first unique discovery. Rutherford
and Oliphant, claiming the right that falls to explorers of new territory,
called the particles tritons and the element tritium. The family of hydrogen
nuclei, until recently consisting of one member, now had three members.

There remained yet another puzzle – that of the lone neutron. Clearly
a pair of diplons contributed two protons and two neutrons to each interaction.
For an instant, a particle with two protons and two neutrons must have existed,
the result of the fusing of the two diplons. In the observed outcome, one
proton emerged alone, and the other proton clumped with the two neutrons
to make a triton. But there was also a neutron that emerged alone. Presumably
this lonely neutron left behind two protons and the other neutron, hanging
together in a particle with two units of charge and three units of mass
– a helium nucleus of mass 3.

DISCOVERY OF A LIFETIME

It was the most important discovery of Oliphant’s career. Of course
the existence of helium-3 was not demonstrated, merely inferred, on the
ground that it was the best explanation. The helium-3 left the target with
such meagre energy – equivalent to a range of 0.6 centimetres in air –
that it defied detection for another two years.

It is not uncommon for major discoveries like these to develop a mythology
that can obscure the historical details. Oliphant has for many years told
a story about Rutherford and helium-3, an anecdote full of vivid detail.
After many hours puzzling over the data, the story goes, Oliphant went home
dispirited at the lack of progress. He was awoken in the small hours by
a phone call from Rutherford, who boomed that he knew the identity of the
short-range particles which had been seen. They were helium particles of
mass 3. Oliphant, taken aback by the suggestion, gently asked what reasoning
lay behind it. The phone shook as Rutherford roared back: ‘Reasons? Reasons,
Oliphant? I don’t need reasons. I feel it in my water!’

Of course the short-range helium particles of mass 3 had not yet been
seen, but the facts do not really matter here. The story is more valuable
for what is says about the Rutherford style, the way his mind worked and
his impact on those around him. Such was the Rutherford spell that even
Oliphant, who was now one of those closest to him, was loath to do anything
of which Rutherford might disapprove.

Such caution caused Oliphant to wait until Rutherford was away before
embarking on a secret investigation. Given that energy was released when
diplons fused together, could more energy be extracted than was needed to
bring the particles together? Could such nuclear fusion be a net source
of energy? With the help of Crowe, Oliphant lashed together equipment which
fired a beam of accelerated diplons into a tube filled with heavy hydrogen
gas. This pioneering experiment came nowhere near succeeding as there was
far too little energy to begin with. But even the attempt was enough to
arouse Rutherford’s ire when he heard about it. Rutherford was adamant that
atomic nuclei could never produce useful energy, calling the notion ‘moonshine’.
Within a decade he was to be proved wrong, with the first uranium fission
reactor going critical in 1942.

In the case of hydrogen fusion, progress has been much slower, and useful
power from fusion reactors is still decades away. If and when the day comes,
Mark Oliphant will have a share in it, at least in spirit. It was he who
first defined the vital reactions between deuterium particles, and first
dared to suggest that those reactions offered a promise of power.

* * *

A life of building particle accelerators for others

Mark Oliphant was never again to be as productive in research as he
had been in those few years at the Cavendish in the 1930s. Thereafter, he
was to be a builder of particle accelerators for others to use.

His success with the deuterium reactions, combined with Rutherford’s
patronage, brought him recognition in the form of an FRS (he is one of the
few to have been a fellow for more than half a century). In 1935 he took
over Chadwick’s old job as deputy director, and oversaw the construction
of two more particle accelerators.

But he was now an attractive candidate for a ‘show of his own’, and
in 1937 the University of Birmingham offered him a chair in physics. It
was a timely move for Oliphant. The influence of the Cavendish in nuclear
physics was waning with the departure of Blackett, Chadwick and others,
and Rutherford died around the time of Oliphant’s departure. At Birmingham,
he quickly secured a massive grant to build the biggest cyclotron in Europe.

The war years saw his influence grow, though his ebullience and openness
were seen by some as an inappropriate lack of discretion. The magnetron,
which turned radar into a war-winning weapon for Britain, was invented and
refined in his Birmingham laboratories. In spring 1940, he was able to
bring the famous Frisch-Peierls memorandum to the attention of the authorities.
Written by two German emigre physicists Otto Frisch and Rudolf Peierls,
the memorandum told of the possibility of an atomic bomb, and stimulated
the formation of the Maud committee and the quest for the atomic bomb.

Oliphant’s friendship with Ernest Lawrence, begun in scholarly dissent,
strengthened in the war years. In 1941, they shook the American scientific
establishment out of its indifference to the military potential of the recent
discoveries in nuclear physics. Once the Manhattan Project was under way,
Oliphant moved his team to Berkeley to work with Lawrence on the electromag-netic
separation of the isotopes of uranium. After the war, shocked by the carnage
of Hiroshima, Oliphant became an evangelist for the ‘peaceful atom’, though
his enthusiasm waned in later years.

In 1950, he returned to Australia to become the first director of the
Research School of Physical Sciences at Canberra’s Australian National
University, which he helped to found. He was the only founding father to
put his own career on the line by taking up a position at the university.
The Canberra years mixed triumph with disappointment. Under his leadership,
the school gained an international reputation. He was instrumental in setting
up the Australian Academy of Science in 1954, and served as its first president.
But his ambitious endeavour to build a massive synchrotron ended in failure.
His critics dubbed it ‘the white Oliphant’.

Oliphant retired in 1962, but in his early seventies he served five
years as state governor of South Australia, bringing his own style to that
office.

David Ellyard is a commentator on science and technology, appearing
on Australian radio and television. He is co-author with Stewart Cockburn
of The Life and Times of Sir Mark Oliphant (Axiom Books, Adelaide, 1981).