On 17 February 2003, John Peter Hobson, a world-renowned expert in the fields of vacuum science and technology and surface science, died suddenly at his home in Ottawa, Ontario, Canada.
Peter was born in Ahmednagar, India, on 25 October 1924. His father, a native of Ireland, was a police officer in the Raj; his mother, a native of Canada, had taught at the University of Saskatchewan before marriage. In 1932, Peter’s parents sent him to boarding school in Ireland, where he was joined by his brother in 1935. In May 1940, his mother went from India to Ireland and sailed with the two boys across the U-boat-infested Atlantic Ocean to the safety of Canada.
After attending high school in Vancouver, British Columbia, Peter joined the Canadian army in 1942, was trained as a radar technician, and was sent to the Pacific theater. When World War II ended, he entered the University of British Columbia and obtained an MASc in engineering physics in 1950.
Peter then went to the University of California, Berkeley, for his PhD. There, he measured the spin of rubidium-81, which has a half-life of only 4.7 hours. To transfer the sample quickly into the atomic beam apparatus, he had to design a vacuum loader—his first foray into vacuum technology.
In 1954, Peter joined the National Research Council of Canada in Ottawa, where he spent 32 years. In 1969, he was appointed head of the electron physics section, which was part of the radio and electrical engineering division. He became assistant director of the division in 1981 and retained that position four years later in the newly formed microstructural sciences division.
Despite his administrative duties, Peter maintained his personal research throughout his career at NRC. His initial research, in 1954, concerned the reflection of very slow (less than 40 eV) electrons from metal surfaces. Allowing sufficient time to make measurements required very low pressures to ensure that the metal surfaces remained clean at the molecular level. Ultrahigh vacuum was in its infancy: Daniel Alpert had announced the Bayard–Alpert gauge, which initiated reproducible UHV only four years earlier, and little UHV equipment was commercially available. The electron physics section had recently started a program to develop UHV techniques, and Peter’s contribution was to investigate cryopumping methods using liquid helium as a coolant. That effort led him to study the operation of vacuum gauges at UHV pressures using liquid-helium-cooled cryopumps. Peter tested the original magnetron cold-cathode gauge, which had been developed in the section, down to 10−12 torr. A version of that gauge was used in the Explorer 17 satellite in 1963; an improved version was later sent to the Moon on the Apollo 12 mission in 1969 to measure the pressure of the lunar atmosphere and was also sent on Apollo missions 14 and 15 in January and June 1971, respectively.
The other major offshoot of Peter’s work on helium cryopumping was a lengthy study of physical adsorption isotherms of helium, nitrogen, argon, krypton, and xenon over a very wide range of pressures from 103 to 10−11 torr. He was able to show that most of those data could be fitted to the Dubinin–Radushkevich isotherm. He also developed a new method of determining heterogeneous binding-energy distributions from physical adsorption isotherms. Peter’s work on the physical adsorption of gases on heterogeneous surfaces at submonolayer coverage has had a profound impact on our understanding of physical adsorption with applications to cryopumping, particularly in accelerators and storage rings.
Peter continued his work on UHV technology for many years. In 1964, he created the lowest pressure ever measured, a record that still stands today, of about 10−14 torr in an alumino-silicate glass system pumped by a liquid-helium-cooled cryopump. He also performed many experiments to establish the physical and chemical processes limiting the lowest pressures obtainable in UHV systems. As a result of his studies on thermal transpiration, Peter invented the accommodation pump in the early 1970s.
The accommodation pump developed a pressure difference between two glass vacuum chambers at room temperature joined by a U-shaped glass tube immersed in a suitable coolant; the surface of one arm of the U-tube was roughened (leached) and the other arm was smooth (fire polished). The proposed mechanism is speculative, but involves non-cosine distribution of gas molecules scattered at the surfaces. In the late 1970s, he participated in the development of an apparatus for transferring a sample from one vacuum system to another while the sample was held at UHV pressures. He demonstrated use of the apparatus by transferring a sample from Ottawa to Vienna, Austria, while maintaining a pressure of less than 10−10 torr.
Peter retired from NRC in 1986 and formed a consulting firm, National Vacuum Technologies Inc, in which he was active until his death. He was a coauthor with us of The Physical Basis of Ultrahigh Vacuum (Chapman & Hall, 1968), which was reprinted in 1993 as part of the American Vacuum Society Classic series.
Peter was very active in AVS: The Science and Technology Society. He was largely responsible for organizing the beginning of the surface science division and was its first chairman from 1968 to 1969. He was a member of the society’s board of directors from 1979 to 1981. In 1990, he won its Albert Nerken Award. Also active in the Canadian Association of Physicists, Peter established the biennial Surface Canada conferences in 1979. In recognition of his efforts, the J. P. Hobson Prize was created in 1983 to honor the best student paper at the conferences.
Peter’s lifestyle was vigorous and competitive. Some of his favorite recreational activities were tennis, jogging, fishing, skiing, curling, and hunting. Until the last two years of his life, Peter and his wife were regular participants in the AVS Run, an event held annually in conjunction with an AVS symposium.
