Simon van der Meer
|Died||4 March 2011 (aged 85)|
|Alma mater||Delft University of Technology|
|Known for||Stochastic cooling|
|Awards||Duddell Medal and Prize (1982)|
Nobel Prize in Physics (1984)
Simon van der Meer (24 November 1925 – 4 March 2011) was a Dutch particle accelerator physicist who shared the Nobel Prize in Physics in 1984 with Carlo Rubbia for contributions to the CERN project which led to the discovery of the W and Z particles, two of the most fundamental constituents of matter.
One of four children, Simon van der Meer was born and grew up in The Hague, the Netherlands, in a family of teachers. He was educated at the city's gymnasium, graduating in 1943 during the German occupation of the Netherlands. He studied Technical Physics at the Delft University of Technology, and received an engineer's degree in 1952. After working for Philips Research in Eindhoven on high-voltage equipment for electron microscopy for a few years, he joined CERN in 1956 where he stayed until his retirement in 1990.
Van der Meer was a relative of Nobel Prize winner Tjalling Koopmans – they were first cousins once removed. In the mid-1960s, Van der Meer married Catharina M. Koopman; they had a daughter (Esther) and a son (Mathijs). He also had a sister (Ge) and a granddaughter.
Simon’s contributions to CERN and accelerator physics speak for themselves.
These started with magnet design in the 28 GeV Proton Synchrotron (PS) era in the 1950s and the 1961 invention of a pulsed focusing device, known as the ‘van der Meer horn’. Such devices are necessary for long-base-line neutrino facilities and are used even today.
That was followed in the 1960s by the design of a small storage ring for a physics experiment studying the anomalous magnetic moment of the muon. Soon after and in the following decade, he did some very innovative work on the regulation and control of powersupplies for the Intersecting Storage Rings (ISR) and, later, the SPS.
His ISR Collider days in the 1970s led to his technique for luminosity calibration of colliding beams, first used at the ISR and still used today at the LHC, as well as in other colliders.
Last but not the least was the Nobel Prize-winning idea behind stochastic cooling and the application of that at CERN in the late 1970s and 1980s, specifically in the Antiproton Accumulator, which supplied antiprotons to the Proton-Antiproton Collider.
During his work at the ISR, Simon developed a technique using steering magnets to vertically displace the two colliding beams with respect to each other; this permitted the evaluation of the effective beam height, leading to an evaluation of the beam luminosity at an intersection point. The famous ‘van der Meer scans’ are indispensable even today in the LHC experiments; without these, the precision of the calibration of the luminosity at the intersection points in the Collider would be much lower.
For the new SPS machine constructed in the early seventies, he proposed that the generation of the reference voltages for the bending and quadrupole supplies should be based on measurements of the field along the cycle, and gave an outline of the correction algorithms. His proposal resulted in the first ever computer-controlled closed-loop system for a geographically distributed system, as the 7 km circumference SPS was; this was a no simple feat for the early 1970s. Measurements of the main magnet currents were introduced only later, when the SPS had to run as a storage ring for the SPS p–pbar collider.
Van der Meer’s accelerator knowledge and computer programming meant he developed very sophisticated applications and tools to control the antiproton source accelerators as well as the transfer of antiprotons to the SPS Collider for Nobel-winning discoveries. The AA and AC pbar source complex machines remained from 1987 to 1996 the most highly automated set of machines in CERN’s repertoire of accelerators.
His prolific inventiveness to the whole park of accelerators at CERN that run so well today for physics, whether they might be for neutrinos sent to Gran Sasso, colliding proton beams at the LHC, or antiproton physics at the Antiproton Decelerator (AD), owe him an immense amount of gratitude. Likewise, the Fermilab antiproton programme that has been running since 1983–85 and the successes of the p–pbar Tevatron Collider up to 2011 and its discovery of the top quark, owe him considerable gratitude.
Van der Meer invented the technique of stochastic cooling of particle beams. His technique was used to accumulate intense beams of antiprotons for head-on collision with counter-rotating proton beams at 540 GeV centre-of-mass energy or 270 GeV per beam in the Super Proton Synchrotron at CERN. Such collisions produced W and Z bosons which could be detected for the first time in 1983 by the UA1 experiment, led by Carlo Rubbia. The W and Z bosons had been theoretically predicted some years earlier, and their experimental discovery was considered a significant success for CERN. Van der Meer and Rubbia shared the 1984 Nobel Prize for their decisive contributions to the project.
Without Van der Meer, particle physics would have probably taken a very different course over the 1980s, 1990s and the early 21st century.
Van der Meer and Ernest Lawrence are the only two accelerator physicists who have won the Nobel prize.
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