MicroscopyPioneers
Scanning Electron Microscope Pioneers Dennis McMullan (1923–2015) and Ken Smith (1928–2020): SEM, Whisky, Chocolate, and Fast Cars
Peter Hawkes* CEMES-CNRS, B.P. 94347, F-31055 Toulouse cedex, France Editor: Cameron Varano, Te Pennsylvania State University, 201 Old Main, University Park, PA 16802
*
peter.hawkes@cemes.fr Te scanning electron microscope has a prehistory, in
Germany and the USA, but the instrument we know today began life in Cambridge in 1948, when Charles Oatley gave “Construction of a scanning electron microscope” to Dennis McMullan as his PhD project. Dennis was born in Reading, England on May 3, 1923, son
of a doctor, and graduated from Cambridge University in 1943. Aſter war service working on radar, and a few years in indus- try, he joined the Cambridge University Engineering Depart- ment (CUED) as Oatley’s first PhD student and brought his project to a brilliant conclusion. Tat first instrument contained all the essential features of the sophisticated instruments we know today. In particular, he designed and built a stabilized power supply and CRT display with a nonlinear video amplifier and introduced double-deflection, which is now standard. He passed on his know-how to K.C.A. (Ken) Smith before leaving Cambridge in 1953. Te years passed, with a high point in 1959 when he married his beloved wife Otti (née Ottilie Sander in Frankfurt, 1917–2004). Among his various posts, he spent sev- eral years at the Royal Greenwich Observatory in Herstmonceux where he developed the “electronographic camera,” a device for enhancing the faint images of distant galaxies. He then returned to Cambridge, to the Cavendish Laboratory, where he spent sev- eral happy and very productive years, working on accessories for the scanning transmission electron microscope (STEM). He was a pleasant, very intelligent, cultivated man, modest concerning his many achievements and at ease with all generations. In old age, life became difficult, but he would have loved the words of his niece at the Mortlake crematorium: “Surely Dennis must be an inspiration to us all for living to 91 years old on a diet heavily influenced by whisky and chocolate!” Te microscope that Ken Smith, Oatley’s second PhD
student, inherited was a remarkable proof-of-concept instru- ment, but it required many improvements if it was to be taken seriously by the electron microscope community, initially very hostile to this newcomer. In particular, he pursued Dennis’s ideas about imaging with secondary electrons and redesigned the specimen chamber in such a way that electrons could travel directly from the specimen surface to the electron mul- tiplier. So successful was his work that an improved model was
60 doi:10.1017/S155192952000111X
ordered by the Canadian Pulp and Paper Research Institute in Montreal. Tis was installed by Ken, who trained the techni- cal staff who would be responsible for this first commercial use of a SEM. A happy side effect resulted from the need to learn specimen preparation techniques and in particular to com- pare SEM images with those obtained in TEM by the replica technique. Ken was instructed in these by Sheila Smith in a completely dark room (dark-adapted vision was essential in those days). Tis was enough to make him wish to see Sheila in daylight, and they were married in 1957. Space does not allow me to describe their happy life in a thatched cottage in a Cambridgeshire village, but I must mention the other love of Ken’s life, his 1933 Alvis Speed 20 Tourer (successor to his Triumph Twin 350 cc motorbike). On his return to Cambridge from Canada, Ken joined the Electron Microscopy Group in the Cavendish Laboratory, headed by V.E. Cosslett, where he was soon invited to direct the construction of the first British high-voltage electron microscope (750 kV) in a site adjacent to the original Cavendish Laboratory in the city center. Tis con- sisted of a large ground-floor room, in which the Cockcroſt– Walton generator and the accelerator unit of the microscope were housed, above a vaulted Victorian cellar, high enough to
Dennis McMullan. Photo: Finn Johannessen.
www.microscopy-today.com • 2020 July
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