David Fiander (1931 - 2015)

It was with shock and sorrow that we heard that Dave Fiander had passed away on 29 March. 

Dave was born in London in 1931 and educated in a number of schools in Wales, finishing up in Swansea. He studied Engineering at Imperial College London – a university which has always enjoyed a premier reputation in the subject. After graduation he worked for several years for the United Kingdom Atomic Energy Authority, where he worked on the production of enriched uranium fuel rods for nuclear power stations. In 1963, he was offered a job at CERN and joined a group in the PS Division headed by Fred Asner and responsible for injection and ejection systems.

This was an exciting time for CERN. Europe’s first large synchrotron, the PS, had been completed and had begun to accelerate bunches of protons to a world record energy of 28 GeV. Once accelerated, the 25 bunches of particles circulated at intervals of 110 ns around the 100-metre-radius circle that was the PS accelerator. These bunches had to be extracted to strike a fixed target from whence a few secondary particles were separated and analysed in momentum to feed a bubble chamber at the far end of the South Hall, which was then CERN’s first large experimental area. Other experiments in the South Hall used scintillation counters, which needed several hundred milliseconds of beam extracted, spilling over a septum through resonant extraction. But bubble chambers required a very short pulse commensurate with the sensitive time of the chamber. The few secondary particles observed in the chamber resulted from a highly selective beam line but started with one or more of the 20 intense circulating bunches in the PS.

Dave’s challenge was to invent a pulsed high-voltage magnet that operated inside the accelerator’s high vacuum chamber and with an aperture big enough for the beam to pass through at injection and strong enough in deflecting field to kick the 28 GeV beam bunches. A septum magnet would then steer the kicked beam out of the machine and onto a target or into another accelerator. The voltage needed to power this “full aperture kicker magnet”, as the device was called, was 60 kV. A length of high-quality coaxial line, charged to this voltage, produced a pulse of tens of kA when a spark gap (later a thyratron switch) was fired. The pulse was fed into the matched impedance of the ferrite cored magnet. The rise time of the pulse had to be less than the 100 ns between bunches, and the pulse had to be rigorously flat, with an equally rapid fall time. Dave’s inventive imagination was brilliant and equal to any of the great accelerator engineers that made CERN possible. He led a small team, Denis Grier, Klaus Metzmacher, Peter Pearce and Stuart Simpson, to complete the device, and founded a generation of many fast switching magnets that, like points in a railroad system, directed CERN’s beams of particles as they threaded their way from Booster to PS to SPS (sometimes diverted via the Antiproton Accumulator and LEAR, and later to LEP, but finally to the Large Hadron Collider). All this was done with characteristic precision and reliability, for a misdirected bunch train might easily bore a hole in the vacuum system or even one of the LHC’s precious superconducting magnets. In spite of all these subsequent projects, Dave was most proud of this first Full Aperture Kicker system and the fact that it is still operational and continues to provide beam pulses today for the CERN accelerator complex.

Dave’s team grew in size to become the BT Group in the PS Division and its responsibilities expanded to include the magnetic septa that followed the kickers. He recruited nationals of many countries and from a variety of engineering backgrounds, leading them to achieve results that none of them as individuals could have hoped for. His secret for gaining their respect was a firm, fair and humane style of management, encouraging new ideas that enabled many advanced pulsed systems to be developed under his leadership.

Dave’s most productive years (he called them his Golden Years) were spent working for Roy Billinge and Eiffion Jones as they put together the Antiproton Accumulator – this needed many pulsed devices for which he built the power supply – for a magnetic horn, and a frightening device, the lithium lens (originally from Novosibirsk), which combined high voltages and current and sent a pulse through a rod of lithium. The slightest leak from the water cooling system would have set this device on fire, and through it travelled the most intense and concentrated beam of protons CERN was able to produce at the time. In Dave’s safe hands this was just another case of “no problem”.

Dave’s last project before taking early retirement in 1993 was the pulsed high-voltage supply for the ISOLDE radioactive beam target station, a project he worked on with Tony Fowler. Yet even in the month he died, he was very proud of the first Full Aperture Kicker, which is still pulsing away after 40 years and is set to do so as long as the PS machine is driving the CERN complex.

We share our sorrow with his family and we convey our deepest condolences and sympathy to Brenda, Susan, Keith, Ian and their families.

His colleagues and friends