Simon van der Mer Dutch physicist, winner of the Nobel Prize in Physics in 1984, together with Carlo Rubbia, Date of Birth: 24.11.1925 Country: Netherlands

Biography of Simon van der Meer

Simon van der Meer, a Dutch physicist and Nobel laureate in Physics in 1984, was born in The Hague. He was the third of four children and the only son of Peter van der Meer, a schoolteacher, and Jetske Grenefeld. His parents valued education and sacrificed financially to provide their children with a good education. van der Meer attended a local grammar school and passed his final exams in 1943, when the Netherlands was occupied by the Germans during World War II. As the Dutch universities were closed by the Germans, van der Meer studied humanities at the grammar school for two more years. However, his interest in physics and technology continued to grow. His favorite pastime became tinkering with electronics. The van der Meer household became filled with various devices and contraptions that he constructed. After the war, van der Meer enrolled in a technical college in Delft to study "control and measurement devices" and graduated in 1952 with an engineering degree. In the same year, he joined the Research Laboratory of the company "Philips" in Eindhoven and participated in the development of electronic microscopes and high-voltage equipment. In 1956, he began working at the European Organization for Nuclear Research (CERN), which was formed two years earlier as a consortium of 13 European countries. At CERN, van der Meer initially worked on the technical design of a particle accelerator called the Proton Synchrotron (PS). Showing a special interest in beam control, he spent several years inventing a pulsating focusing device, which he named the "neutrino horn." This device was designed to increase the intensity of neutrino beams, which are elementary particles with no electric charge and almost no mass. Neutrinos are emitted along with other particles in reactions such as beta decay (emission of electrons) of radioactive nuclei. In 1965, van der Meer designed a small storage ring device used in experiments to measure the magnetic properties of muons, which are particles similar to electrons but much heavier and were initially discovered in cosmic rays. His involvement in this experiment allowed van der Meer to become familiar with the principles of accelerator design and the characteristic thinking of physicists working in the field of high energies. From 1967 to 1976, van der Meer was responsible for the power supply of the intersecting storage rings at CERN and the Super Proton Synchrotron (SPS) at 400 billion electron volts. Intersecting storage rings allow particles, such as protons, to circulate in opposite directions in two different rings. At the points where the storage rings intersect, the colliding beams interact. In 1976, van der Meer became a participant in a project proposed by Carlo Rubbia, David Cline, and Peter McIntyre. The essence of the project was to convert the SPS into an experimental setup for the detection of hypothetical W and Z particles (bosons) associated with nuclear (strong) interaction. The search for these particles had been underway for many years and their discovery would have been crucial in confirming quantum field theories. Physicists distinguish four fundamental interactions: gravitational (attraction between masses, holding the universe together), electromagnetic (binding atomic electrons to the nucleus, atoms to other atoms in molecules, and underlying all chemical processes), weak interaction (responsible for certain types of radioactivity, such as beta decay), and strong interaction (holding protons, neutrons, and other subatomic particles together in the nucleus, compensating for opposing forces such as the repulsion of tightly packed protons). According to the quantum field theory, interaction occurs through the exchange of fundamental particles, or quanta of the field. Max Planck, the father of quantum theory, discovered in 1900 that energy is emitted not continuously, but in discrete portions, or quanta. In 1905, Albert Einstein confirmed quantum theory by demonstrating that light, whose wave nature had been widely accepted for centuries, can also act as a stream of individual particles. The quantum of light, like the quantum of any electromagnetic radiation, became known as the photon. Electromagnetic interaction occurs through the exchange of photons. The energy of a photon is proportional to the frequency of radiation. In 1935, Japanese physicist Hideki Yukawa hypothesized that the internal interaction of the nucleus could be carried by quanta with rest mass and calculated its presumed value to be about 200 electron masses. In 1947, English physicist Cecil F. Powell discovered Yukawa's particle in high-altitude collisions between cosmic rays and nuclei. Since a lighter, but similar, particle had been found earlier at lower altitudes, Yukawa's particle became known as the pi-meson, or pion, and the lighter particle became known as the mu-meson, or muon. The pion plays a role in the strong interaction, connecting protons and neutrons, as well as same-charge subnuclear particles (either protons or neutrons). The existence of four fundamental interactions did not satisfy physicists. Several attempts were made to create a theory that unified all four interactions within a single framework. In 1960, American physicist Sheldon L. Glashow proposed the electroweak theory, which unified the electromagnetic and weak interactions. Glashow's theory required the existence of three bosons (named after the Indian physicist Satyendra Nath Bose): a positively charged W+ boson, a negatively charged W- boson, and a neutral Z0 boson. The W bosons were to serve as carriers of the weak interaction, and all three new bosons, along with the photon, were to mediate the electroweak interaction. Seven years later, American physicist Steven Weinberg and Pakistani physicist Abdus Salam independently predicted that the W and Z bosons should be tens of times heavier than any previously known elementary particle and have an extremely short lifetime (less than 10^-18 seconds). Italian physicist Rubbia, who had been working at CERN since 1960 and conducting W and Z particle searches at the Fermi National Accelerator Laboratory near Chicago, succeeded in persuading CERN management in 1979 to rebuild the SPS for such research. The estimated cost of the project was $100 million. Since the masses of the W and Z particles are large, their observation requires the release of a tremendous amount of energy. The equivalence of mass and energy, derived from Einstein's theory of relativity, allows the estimation of the required energy. The estimated amount exceeded the capabilities of existing particle accelerators, primarily because not all the energy is used to create new particles in collisions between high-speed particles. Rubbia and his colleagues proposed using the SPS as a proton-antiproton collider on intersecting beams. Antiprotons are particles of antimatter, identical to protons except for their electric charge, which is negative. The existence of the first antiparticle, the positron, was predicted in 1928 by Paul A.M. Dirac. It was experimentally discovered by Carl D. Anderson in 1932 and named the positron. When particles and antiparticles collide, they annihilate each other, releasing energy in the form of, for example, gamma radiation. In the modified SPS, protons and antiprotons, as particles with opposite electric charges, circulated in opposite directions within the same magnetic field inside the same ring. When the particles collided, the energy released would be sufficient to produce W and Z particles. The realization of the project faced many difficulties: problems with accumulating the necessary number of antiprotons in a sufficiently intense beam (antimatter particles are extremely rare) and with designing a detector capable of identifying particles and determining their characteristics. The lifetime of the particles is too short to observe them directly, but the products of their decay can provide valuable information. One of the products was expected to be the elusive neutrino, which has unusual properties, including the absence of charge and mass, making it nearly impossible to interact with matter and trigger any detector. Physicists infer the existence of neutrinos by summing up the energy and momentum of other decay products in all directions and determining the missing energy and momentum. Rubbia and over a hundred other scientists built a complex 1200-ton detector chamber. Another group built a smaller 200-ton detector to confirm the results obtained. van der Meer managed to solve the problem of delivering antiprotons by designing a dedicated storage ring. To produce antiprotons, a stationary copper target was bombarded with bunches of protons accelerated to high energies on the old PS. The produced antiprotons arrived in rapid succession into the storage ring. Accumulated in the ring for about a day, the antiprotons were injected back into the PS for preliminary acceleration and then into the SPS, where they were joined by a previously accelerated group of protons also extracted from the PS. The protons and antiprotons were finally accelerated to energies of about 300 billion electron volts. The SPS was transformed into a gigantic storage ring with a circumference of over 12.5 miles, where particles and antiparticles, divided into three groups, circulated in opposite directions and collided head-on at six precisely defined points. Detectors were placed at two of these points. The key moment in the successful creation of the antiproton accumulator was the implementation of van der Meer's stochastic cooling. Each injected bunch of antiprotons had to be compressed into a dense narrow pulse and attached to an increasingly numerous swarm of antiprotons flying along the axis of the evacuated chamber. The resulting cloud of antiprotons had to be stored in such a way that it would not interfere with the flow of new bunches. The complex control system included a series of pickup electrodes (sensor electrodes) that monitored the particle orbits and sent properly amplified signals to the electrodes located ahead, which, through corrective "nudges," focused the trajectory into a narrower beam when a bunch of particles reached the correction points. Other nudges adjusted the speeds of the compressed bunches to allow them to merge with the accumulated ones. In this context, cooling refers to reducing the speeds of particles relative to each other. Stochasticity implies the randomness that is inevitable when dealing with a large number of particles. van der Meer later said that "such a complex process could not have been overcome without the efforts and dedication of several hundred people." Collisions between protons and antiprotons, making 50,000 revolutions per second around a ring with a circumference of over 12.5 miles, allowed the achievement of record-breaking energies for that time. The collider was put into operation in 1982, and the discovery of the W+ and W- particles was announced in January 1983. A few months later, the discovery of the more elusive Z particle followed. van der Meer and Rubbia were awarded the Nobel Prize in Physics in 1984 "for the decisive contributions to the large project, which led to the discovery of the field particles W and Z, the carriers of weak interaction." The experimental discovery of weak interaction quanta was enthusiastically received worldwide as one of the most important achievements in physics in the 20th century. The discovery of the W and Z particles explained why the Sun does not overheat and incinerate all life on Earth, made the so-called "big bang theory" in cosmology more plausible, and brought science closer to the possible realization of Einstein's dream, albeit in a modified form, of creating a unified field theory encompassing all four fundamental interactions in nature. van der Meer continues to design and build increasingly sophisticated storage rings at CERN. Since 1966, van der Meer has been married to Catharina M. Koopman, and they have a son and a daughter. He is an avid skier and hiker and enjoys reading fiction in his leisure time. van der Meer has been awarded honorary doctorates from the University of Geneva, the University of Amsterdam, and the University of Genoa. He has also received the Duddell Medal and the London Physical Society Prize (1982). He is a member of the Royal Netherlands Academy of Arts and Sciences and the American Academy of Arts and Sciences.