Frank Krienen (1917-2008)

Amsterdam, summer 1952: it was here that the first recruits for CERN ‘s 600 MeV Synchrocyclotron project met Frank Krienen for the first time. A young assistant to Prof. C.J. Bakker at the Physics Institute, he soon became the mastermind behind the most daring aspects of the project: the frequency modulating circuit, based on a vibrating tuning fork, was his creation.

He was a respected and inspiring leader throughout the construction period of the accelerator and, at the same time, an older brother and an exacting mentor. Frank later devoted himself to developing particle detectors, in particular spark wire chambers using different types of readout. His next major involvement at CERN was his contribution to the glorious g-2 saga.

Frank’s contributions to the last experiment of the anomalous magnetic moment of the muon (g-2) done at CERN (1969-1977) were very important in many aspects. The last (g-2) experiment was based on many innovative solutions and Frank’s contributions were remarkable. In particular he was in charge of the construction and operation of the electric quadrupoles necessary to provide the vertical focusing of the muon beam in the Storage Ring. Frank’s colleagues working in the g-2 appreciated not only his technical competence but also his originality in proposing new solutions, and also his strong personality. He was a great friend.

The cooling of antiprotons à la Budker using an intense electron beam was his next project. Although not used in the first version of the antiproton source, this was later incorporated in the low-energy ring LEAR. Later stages in his long and fruitful career, after leaving CERN, took him to Stanford and Brookhaven, where he continued his involvement in the newest g-2 programme. Frank’s contributions were important, especially in a clever design of the inflector that was a real breakthrough in the experiment.

Based successively in California and in New England, he lived for years in Florida, from where he travelled regularly to follow his many scientific and personal interests. He was a regular visitor to Europe and to CERN, always welcomed by his colleagues. Gifted with a curious, inquisitive mind, Frank had an excellent training both in physics and in engineering. He remained active to the last, well beyond his 90th birthday. Frank Krienen was spared the degrading decay so often synonymous of very old age: his life ended in a tragic road traffic accident in Amsterdam on 20 March 2008.

His many friends remember him, thankful for having been close to such an exceptional person. All his friends and colleagues at CERN express their deepest sympathy to Anneke, his wife, and Fenna and Frankie, his two children.

His friends at CERN