A Lab of Honour

Last Friday, my first day in post here at the University of Sussex, there was a small ceremony to mark the formal opening of a new undergraduate teaching laboratory. Appropriately, it was named after Professor Ken Smith who died last year. Professor Smith was an outstanding experimental physicist who joined the University of Sussex way back in 1960 before the campus had even been built. Over the next three decades, as well as developing a new research activity in which the Department is now world-leading, he made substantial contributions to laboratory teaching in particular. He also played his part in the administration of the Department, serving as the first Chairman of Physics, and then as Dean of the School of Mathematical and Physics Sciences (MAPS) and later as Laboratory Director. Prof. Smith retired in 1988, which was the year I finished my DPhil from the (then) School of Mathematics and Physical Sciences.


Anyway, it was a pleasant occasion at which Prof. Philip Harris (to the left of the picture), Head of the Department of Physics & Astronomy, spoke of Professor Ken Smith’s many achievements, Ken’s widow Verena unveiled the commemorative plaque, and we all gathered for tea and cakes in the foyer so as not to disturb further the students still hard at work at their experiments…


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One Response to “A Lab of Honour”

  1. Ray Essen Says:

    Ken Smith’s contribution to the first Atomic Clock

    This year marks the 60th anniversary of the invention of the atomic clock and it seems a suitable time to put on record the contribution made by Professor Ken Smith to the operational success of the first caesium-beam atomic clock built by my father-in-law, Louis Essen, in May 1955. At that time, Ken was a lecturer working with Otto Frisch in the Cavendish Laboratory, Cambridge, and was the only molecular-beam physicist operating in the UK. Louis Essen had started to assemble the atomic clock in late 1954 but had encountered a few problems in establishing the correct path of the atoms through his apparatus so had contacted Otto Frisch who passed the job on to Ken.
    I spoke to Ken in 2004 and we corresponded over a few weeks. The following extract is taken from one of Ken’s emails, “Frisch suggested to me that I might pay a visit to NPL [National Physical Laboratory] and help to sort out the problems. When I went to NPL I found that Essen’s assistants were having problems with the vacuum system and the detector which were easily sorted. I found that the deflecting magnets were deflecting all the atoms on to the pole faces, even when the [rf] currents were off. After calculating the atom trajectories through the system, and making some power supply changes to allow effective demagnetisation, we were soon able to see the zero frequency transition and the low frequency transition at the calculated frequency. This allowed more careful adjustment of the apparatus to improve signal to noise and the hyperfine low field transition at 9192 KHz was found when the high frequency was connected”.
    A few weeks later, Essen’s atomic clock was fully operational and measurements made with the clock were then used to calculate the atomic frequency of the caesium atom – which now forms part of the definition of the SI unit of time (the ‘second’).
    To celebrate the anniversary of the operation of the first practical atomic clock, I am publishing a book, The Birth of Atomic Time, which tells the story of its invention and the important role played by Professor Ken Smith.

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