# Accelerator tradition is thriving at Brookhaven

22 February 2002

When the Brookhaven National Laboratory was established in 1947 at Long Island’s Camp Upton, it inherited barracks, recreational facilities and a stockade for prisoners of war. Today the barracks remain, converted into offices, but the stockade has given way to world-class research facilities that cover topics from particle physics to the environment.

Brookhaven, funded today by the US Department of Energy, was born of the dreams of scientists returning from Los Alamos after the Second World War. They were looking for facilities to continue their research into the mysteries of the atom and they were unable to find them at their home universities. Soon, championed by Columbia physicists Isidor Rabi and Norman Ramsay, the idea of universities coming together to build a common research institute began to take shape. In 1947, nine north-eastern US universities clubbed together to form Associated Universities, Inc. with the goal of establishing a laboratory, and the model for many of today’s major laboratories, including CERN, was set.

### Man-made cosmic rays

Not long after, plans for the Cosmotron – Brookhaven’s first particle accelerator – were laid. Taking its name from the cosmic rays that constantly shower down on Earth, the Cosmotron was the first accelerator to break the giga-electronvolt barrier, reaching energies as high as 3.3 GeV before it was switched off in 1966. The fact that it was also the first accelerator in the world to provide an extracted beam led to the Cosmotron being dubbed the world’s biggest slingshot by Popular Science magazine.

Scientifically, the Cosmotron lived up to its name, allowing all kinds of particle formerly seen only in cosmic rays to be studied in the laboratory. It was also the machine behind Brookhaven’s first Nobel prize. Two guest scientists working at the laboratory in 1956 – T D Lee and C N Yang – interpreted Cosmotron data as arising from parity violation in weak interactions, earning themselves a trip to Stockholm just one year later.

It is perhaps to accelerator physics that the Cosmotron left its greatest legacy, however. From the start, the Cosmotron’s builders recognized the limitations of synchrotrons as they were used at the time. In such machines, increasing particle energy was invariably accompanied by increasing orbit instability in the horizontal plane. To build a more powerful machine would require more powerful – and vastly heavier – magnets, imposing a practical upper limit on the energy achievable. The solution, developed by Ernest Courant, Stanley Livingston and Hartland Snyder in the 1950s, was to alternate the horizontal orientation of the bending magnets so that the field gradients in the horizontal plane also alternated. This principle became known as strong focusing and it opened the door to much higher energies.

By this time, Europe’s new laboratory, CERN, was getting off the ground. It was founded on the Brookhaven collegiate model with member states taking the place of Brookhaven’s universities. Links between the two laboratories were close and news of the strong focusing idea reached the European laboratory in time for it to recast its new proton synchrotron (PS) as a strong focusing machine. The CERN PS duly became the first operational, strong-focusing proton synchrotron in the world with a design energy of 25 GeV instead of the 10 GeV that would otherwise have been possible. Brookhaven’s Alternating Gradient Synchrotron (AGS) came on stream soon after and these two machines remain at the heart of the two laboratories’ accelerator complexes to this day.

The AGS has provided a rich harvest of physics for Brookhaven, earning the Nobel prize three times. Leon Lederman, Melvin Schwartz and Jack Steinberger had to wait until 1988 to receive the prize for their 1962 discovery of the muon neutrino. James Cronin and Val Fitch had a shorter wait, receiving the call to Stockholm in 1980 for their 1963 observation of CP-violation. Sam Ting picked up the prize for his 1974 discovery of the J/psi particle, along with Burton Richter of California’s SLAC laboratory, just two years later.

### Physics in collision

Flush with the success of the AGS, Brookhaven set its sights high and in 1970 accelerator physicist John Blewett revived an earlier idea of building a machine to store and collide proton beams. Named project ISABELLE, Blewett’s plan was to build a pair of intersecting storage rings using the AGS as the injector. R&D for the new machine soon got under way and a ground-breaking ceremony was held in 1978. Soon after, however, a mixture of technical problems and changing political winds led to ISABELLE being dropped in favour of an even more ambitious project elsewhere – the Superconducting Super Collider – the downfall of which was later to send shockwaves around the world’s particle physics community.