The following correction was printed in the Guardian's Corrections and clarifications column, Wednesday March 28 2007
The eponymous inventor of the Van de Graaff generator/accelerator was Robert J Van de Graaff, not Van der Graaf as we had stated. This has been corrected.
Professor Jack Boag, who has died at the age of 95, was a leading figure in the science of cancer radiation therapy, and also played a part in the ending of the cold war through his involvement in the Pugwash group of scientists.
Born in Elgin, north-east Scotland, and brought up in a modest Glasgow family, he gained a degree in electrical engineering from Glasgow University and went to work for the British Thomson-Houston (BTH) engineering company in Rugby. A scholarship to St John's College, Cambridge, enabled him to work at the Cavendish laboratory, and in 1934 he began a PhD project at Braunschweig, in Germany.
The consolidation in power of the Nazi party in Germany forced his return to BTH in 1936, and in 1942 he started working for the Medical Research Council's new radiotherapeutics research unit at Hammersmith hospital, west London. At that time cancer treatment by radiation was in a primitive state, and there was a desperate need to develop sources of radiation that could penetrate down to deep-seated tumours without damaging skin and intervening tissues. Jack's first project was therefore to design and build a two-megavolt Van de Graaff electron accelerator (forerunner of the modern linear accelerator) that would provide a source of penetrating x-rays.
This led on to his lifelong interest in the question - still not fully answered - as to how it is that x-rays cause lethal damage to tumours and other tissues; and how best to make a physical measurement that will accurately quantify that damage (thereby enabling clinical treatments to be designed for optimum balance between effectiveness and safety). In 1953-54 Jack was a visiting scientist at the US national bureau of standards, and on his return to London worked with Joseph Rotblat (obituary, September 2 2005) at Bart's hospital.
In 1958 a radiobiology research unit was set up at Mount Vernon hospital, in Northolt, west London, and it was there that Jack did his most significant research work, investigating the fast chemical reactions that occur following exposure to radiation and that lead to its damaging effects.
By 1965 he had become the obvious candidate to replace Val Mayneord (obituary, August 26 1998) - then effectively the doyen of the international medical physics community - as professor of physics at the Institute of Cancer Research and Royal Marsden hospital. At that time the institute was a rather loose confederation of three effectively independent groups: physics (under Mayneord), radiotherapy (under Sir David Smithers) and the Chester Beatty Institute (under Sir Alexander Haddow, and owing its name to its original benefactor, a Rhodesian copper magnate). Haddow was a man of considerable scientific achievement but had little respect for accountants and, following his retirement and an inspection by the Medical Research Council, drastic action needed to be taken.
Thus it was that Jack, as the heavyweight and relatively independent new boy, found himself made chairman of the interim committee - in effect the first overall director - tasked with the unenviable job of downsizing the institute. This all resulted in much unhappiness and hard feelings - some of it rather unfairly directed at Jack - but it is much to his credit that the institute pulled through to become, as it now still is, with the Royal Marsden, one of the world's leading cancer centres.
Jack's former colleague and close friend Rotblat was a driving force behind the international Pugwash conferences on science and world affairs. He was also a vigorous arm-twister in a good cause and, following his retirement in 1976, Jack soon found himself an active member of Pugwash.
It was in this connection, helped by his fluency in Russian, that Jack and Rotblat were asked to join the conference convened in Moscow in February 1987 by the USSR president Mikhail Gorbachev, to advise him on the technicalities of how best to end the cold war. Later that year, Gorbachev himself corresponded with the Pugwash group on the particular issue of conventional weapons, and shortly afterwards unilaterally withdrew 10,000 Soviet tanks from eastern Europe - a move that led to the 1990 Conventional Forces in Europe Treaty. Jack had thus taken a hand, not only in rescuing a cancer institute, but also in rescuing the world from potentially nuclear confrontation.
In 1938 Jack married Isabel Petrie, who predeceased him at their home in Edinburgh last July. They were both active Quakers and had no family.
· John 'Jack' Wilson Boag, cancer scientist and peace campaigner, born June 20 1911; January 2 2007
