Simon van der Meer (1925-2011)

Simon van der Meer was a true giant of modern particle physics, though a gentle one. His contributions to accelerator science remain vital for the operation of accelerators such as the LHC today. Simon was an electrical engineer who grew up in The Hague, moving on to Delft University to study electrical engineering. After a short stint with Philips, he came to CERN in 1956, just two years after the lab opened, and remained with us until his retirement in 1990.

Simon was an incredibly inventive man. When confronted with a problem, he would sink into deep reflection, rarely emerging until he had a solution. One of us, Steve Myers, remembers him as a man who did not suffer fools gladly, and who was extremely taciturn. Simon would never use two words where one would suffice. But that one word would invariably be the right one.

Simon is best known for his contribution to the SPS collider project, for which he was awarded the Nobel Prize, jointly with Carlo Rubbia, in 1984. Stochastic cooling, the innovation that made the SPS collider possible was typical of a Simon van der Meer invention: deceptively simple at first sight, but to anyone who truly understands accelerators it was nothing less than a stroke of genius.

Stochastic cooling is a technique used to keep intense beams of like-charge particles together. Essentially it involves measuring the size and momentum distribution of the beam particles at one point on the accelerator ring, and sending the information needed to corral the beam across the middle of the ring so that it arrives early enough to be used to apply the necessary corrections.

This may have been Simon’s greatest contribution to modern physics, and it was justly rewarded with the Nobel Prize, but in the early days, Simon took some convincing that this idea was so important. To our knowledge, Simon first mentioned the possibility of stochastic cooling at an ISR group leaders’ meeting in 1968. Wolfgang Schnell, who was group leader of the RF and beam instrumentation group, had a devil of a time convincing Simon to write up his ideas, but eventually he did and so began his journey to Stockholm.

The next step on the road was ICE, the Initial Cooling Experiment, designed to put stochastic cooling to the test. The idea worked beautifully, and ICE proved a key element in persuading the CERN Council to go ahead with the SPS collider project. It was then a natural choice that Simon should be one of the leaders of the Antiproton Accumulator project, which used stochastic cooling to accumulate enough antiprotons for the collider. That too was an unqualified success, and the rest, of course, is history.

Simon came to CERN as a specialist in power converters, and he was responsible for building those used for the world’s first hadron collider, the ISR, and later for the SPS. He also developed a device known as the magnetic horn, versions of which today allow laboratories on three continents to direct focused beams of neutral particles – neutrinos – through the earth for hundreds of kilometres to underground particle detectors. And another part of his legacy is the technique he developed for measuring beams that bears his name. Without “van der Meer scans”, the precision of the calibration of the luminosity in the LHC would be much lower. At CERN today, it’s fair to say that Simon’s contributions continue to play a significant role in projects from the LHC to the CERN neutrinos to Gran Sasso project, and the Antiproton Decelerator – whose 2010 results were honoured with the distinction of breakthrough of the year by Physics World magazine. Simon was a brilliant all round technologist and scientist, well respected at CERN and around the world. A true giant of our field.

Rolf Heuer and Steve Myers