Marcus Laurence Elwin “Mark” Oliphant, a leader during World War II in both radar development and the separation of uranium-235 for the atomic bomb, died on 14 July 2000 in Canberra, Australia, of natural causes.
Oliphant was born in Adelaide, South Australia, on 9 October 1901. In 1927, he received an MSc in physics at Adelaide University and won an 1851 Exhibition scholarship for research abroad. He joined Ernest Rutherford’s group at the Cavendish Laboratory in Cambridge, England. He received a PhD in physics there in 1929; his thesis topic was the interaction of positive ions with metal surfaces.
In 1932, Oliphant began nuclear research with Rutherford, using 0.5 milliliters of heavy water given to Rutherford by Gilbert Lewis of the University of California, Berkeley. With a 300-keV accelerator, Oliphant and Rutherford investigated the transmutation of light nuclei, bombarding them with protons and deuterons (heavy hydrogen). Remarkably, with deuterated targets, “protons” of anomalously large range were emitted jointly with very slow protons. Oliphant and Rutherford realized that these “protons” were “still-heavier hydrogen,” which they named “tritium,” and that the “alpha particles” they saw were helium-3.
Oliphant joined Birmingham University in 1937 as Poynting Professor of Physics. While visiting primitive radar stations around Britain’s coast, he realized that much finer radar was needed urgently. Early in 1939, he obtained a grant from the British Admiralty to develop radar with a wavelength less than 10 cm; the best available at the time was 150 cm.
That same year, he visited the Radiation Laboratory at Berkeley, California, where he met Ernest Lawrence, who would become a major influence in Oliphant’s life. Oliphant was impressed by Lawrence’s 60-inch cyclotron. Lawrence kindly gave him a complete set of specifications. In mid-1939, having gained funding, Oliphant began to build a 60-inch cyclotron at Birmingham. This project progressed slowly because of the war. An internal beam was achieved in 1950.
Congratulating Lawrence on his 1939 Nobel Prize in Physics for the invention of the cyclotron, Oliphant wrote, “[Your Nobel] Prize shows that the technical side of the subject is now recognized as of equal importance to the advances that follow from [their use].” This view would soon govern Oliphant’s scientific life.
On radar research at Birmingham, John Randall and Harry Boot soon invented the resonant-cavity magnetron. In early 1940, their model achieved the wavelengths needed. The magnetron’s power was soon increased 100-fold, and Birmingham concentrated on magnetron development. The first operational magnetrons were delivered to the US in August 1941.
Also at Birmingham, in 1940, Otto Frisch and Rudolf Peierls had calculated that production of a uranium-235 atomic bomb of modest size was quite feasible. Oliphant took their memorandum at once to higher authority. A committee, code-named MAUD, discussed the memo and sent a report to the US “uranium committee” around June 1941; no reply came. When Oliphant visited the US in August, he found that the uranium committee secretary had simply locked the memo in his safe, telling nobody, because the US was “not at war.” Oliphant found little interest in atomic bombs among the physicists, most thinking them improbable. Only when Oliphant visited Lawrence in September did he get any response, which prompted him to give Lawrence a brief summary of the MAUD report. Lawrence then took Oliphant’s story directly to James Conant, chairman of the US National Defense Research Council, and Arthur Compton, provost at the University of Chicago, and convinced them that they should take the British work very seriously.
In November 1943, Oliphant moved to work on the Manhattan Project, joining Lawrence’s group on electromagnetic separation of 235U from 238U for the atomic bomb. Most of his time was spent either at Berkeley or at Oak Ridge, Tennessee. He resigned from the Manhattan Project in January 1945, returning to Birmingham. He received funds from the postwar UK atomic energy committee for a 1-GeV proton synchrotron at Birmingham. He later (1950) left Birmingham for Canberra with key technicians. The proton synchrotron’s chief designer died in 1950, and Philip Moon completed its construction in 1953.
When Oliphant learned details of the sufferings of the Hiroshima and Nagasaki populations, following the detonation of the two atomic bombs, he was appalled, feeling deeply guilty about his part in constructing the bombs. Concluding that all war was evil, he cut his links with military work. He came to believe that scientists must become more concerned about the social effects of their work. He became a founding member of the Pugwash Movement, attending the first three Pugwash conferences (between 1957 and 1958). He participated in another run of four conferences (1961–64). An impressive individual, tall with thick, white hair, he spoke convincingly and energetically; he described himself as “a belligerent pacifist.”
The Australian government wished to found an Australian National University (ANU), dominantly for research, and formed a committee (which included Oliphant) to plan this ANU project. In 1950, Oliphant became the research director for ANU’s physical sciences division and the professor of particle physics. He required funding for a new accelerator there; the funding was granted to him. The purpose of Oliphant’s accelerator was to produce 10-GeV protons at low cost. The high cost of iron magnets favored the choice of an air-cored synchrotron structure; the high magnetic fields needed for accelerating the protons in the synchrotron would be generated by the electric currents resulting from the short-circuiting of a power supply. For this source, he built a homopolar generator (HPG) on-site. The HPG could be energized in 10 minutes by electricity mains, and then short-circuited. The final accelerated proton beam would then emerge in pulses of six per hour, an unusually low repetition rate. Oliphant argued that these 10-GeV protons, although few, would carry vital new information.
Quite early, Oliphant believed that the currents received from the HPG would be so large—outside engineering experience—that their collection would require the use of liquid-jet brushes. He opted for a mixture of sodium and potassium, NaK—liquid at room temperature, but a dangerous material. In 1962, the HPG ran regularly, until an explosion occurred, resulting in serious injury even though safety regulations were followed. After an inquiry, in which Oliphant and his coworkers were exonerated, one coworker tried conventional (copper–graphite) brushes, which worked smoothly and have continued to do so.
An external report, obtained for ANU, on the accelerator project indicated that the HPG was “hopelessly inadequate” for its original purpose. Oliphant’s group began to go their various ways. He resigned his directorship in 1963. Until his retirement in 1967, he worked as a research professor on ionized gases.
In retirement Oliphant remained a public figure. He wrote articles on physics topics, published in the newspapers and in popular journals, and participated with zest in public debates on issues of general interest. He was frequently asked to give funeral and university orations. In 1972, he began a five-year appointment as the governor of South Australia. He was an open-minded governor and became popular with the public. In 1977, he participated in his last Pugwash conference, held in Munich. His activities continued but gradually diminished, although the impulse was always there.
