The Origins of RHIC
By Robert P. Crease
How RHIC came into being is a remarkable story that illustrates what historians call recombinant science, where new and innovative things result from putting together many existing pieces in a novel way. The story takes place in three “acts,” so to speak. Act I involves an accelerator project called ISABELLE, which was proposed in 1972, approved in 1978, and terminated in 1983. Act II is about what made it possible for the ISABELLE project to be transformed into RHIC. Act III takes place in a single week in July 1983, when this transformation took place.
Act I: Life and Death of ISABELLE
In 1972, Brookhaven submitted to the AEC a proposal to construct a 200 x 200 GeV colliding beam accelerator called ISABELLE (Intersecting Storage Accelerator + BELLE for beauty). The justification, made by a committee headed by Val Fitch, had three components. The first was a new confidence in the viability of colliders, in large measure due to the success of the Intersecting Storage Ring (ISR) facility that had just been constructed at CERN. The second was a specific target, the W, for planners felt that ISABELLE’s parameters made it all but certain that this particle would be discovered. The third was a new confidence in superconducting accelerator magnets, which had been pioneered at BNL. Together these three justifications made ISABELLE the most rational next step for BNL and for the US high energy physics community.
But science was changing rapidly. New discoveries, especially of the J/psi in 1974, boosted the interests of physicists in higher energies and high Pt. And ISABELLE faced competition from accelerator projects at other labs. In 1977 -- under pressure for scientific and political reasons -- the lab raised ISABELLE’S energy to 400 x 400 GeV by slightly increasing the size of the ring, and the magnet power to 5T. The ISABELLE project was then approved at a HEPAP subpanel meeting at Woods Hole in 1977. Groundbreaking was in October 1978. But problems with the magnets, with double-digit inflation, and political factors caused the US physics community to lose enthusiasm for ISABELLE, and to put all its eggs in the SSC basket. Though the magnet problems were solved, the ISABELLE project (briefly renamed CBA) was terminated in 1983.
"Quenched! The ISABELLE Saga, I" Physics in Perspective 7 (2005) 330-376.
"Quenched! The ISABELLE Saga, I" Physics in Perspective 7 (2005) 404-452.
Act II: New Idea
How was it possible for the ISABELLE project to be converted into RHIC? This is the subject of ACT II. In the funny way in which science works, however, the events of ACT II take place at the same time as those of ACT I.
One key factor was rising theoretical interest in heavy ion collisions among both nuclear and high energy physicists. Among nuclear physicists, the nucleus is a marvelous laboratory for collective effects. During the 1970s, however, nuclear collisions also became of interest to high energy physicists. The interest came in two phases. The first phase was due to the idea of “Lee-Wick matter,” promoted in the early 1970s by T. D. Lee and Gian-Carlo Wick. The second phase came in the latter half of the 1970s, following the discovery of the J/psi, the development of QCD, and the appearance of the possibility of a new phase of matter, “quark-gluon plasma.” Thus while at the beginning of the decade there was little theoretical interest in relativistic heavy ion collisions, by the end of the 1970s, nuclear physics and mainstream quantum field theory intersected in this idea of the possibility of a quark-gluon plasma.
A second factor was experimental interest. At the beginning of the 1970s, a small amount of heavy ion experimentation had been conducted at the Princeton-Penn Accelerator, before it was shut down in 1972. But experimental interest grew during the 1970s, mainly at Berkeley’s HILAC, upgraded to the super-HILAC and then to the BEVALAC, which came on line in 1974 at 2 GeV per nucleon. The work there generated so much interest that a panel called NSAC, the nuclear physics equivalent of HEPAP, began planning heavy ion facilities on the long term the way HEPAP planned future high energy accelerators on the long term.
A third factor was a series of hardware assets at BNL, either complete and looking for new missions, or in the planning stages. These included the Tandem Van de Graaff, the Transfer Line, the Booster, the AGS, and of course ISABELLE’s footprint – its completed conventional construction.
A fourth factor was BNL’s existing nuclear physics experimental program. And a fifth factor was leadership, which involved a difficult juggling act. When the ISABELLE project ran into difficulties, BNL lab director Nicholas Samios had to keep pushing the lead project – ISABELLE as a high-energy machine – but with viable alternative if that should not pan out. But it couldn’t be too viable, or that viability would threaten the already troubled main project – and thus alternate project as well. He wanted to keep something on the back burner, but not let it burn too brightly. As T.D. Lee once explained, Samios was like commander of a ship trying to get into a difficult harbor. He had to stay dead on course and not waiver trying to get into the harbor, but always have an alternate harbor in mind in case he failed. But – and this was the hard part – the seas being what they were, he couldn’t head for that alternative harbor too soon or he wouldn’t get into either port. And Samios had to promote the pieces – Transfer Line, Booster, and so forth – carefully, proposing them as independent projects, but with the unstated assumption that they would be parts of the yet to be approved machine.
ACT III: Turnabout
The turnabout between ISABELLE/CBA and RHIC came about more or less (it is not quite that neat) in a remarkable five-day period, July 11-15.
ACT III takes place over the course of 5 days. On Monday, July 11, lab employees found a memo from Samios in their boxes telling them about the decision. The memo said that possible directions for the future include “a device for extremely high energy heavy-ion collisions using the CBA tunnel and superconducting magnets.” He announced an all-hands meeting of lab employees for Wednesday. By a phenomenal coincidence, that very day, NSAC was meeting at Wells College in upstate New York. On the committee was BNL ISABELLE experimenter Tom Ludlam. He used the lab plane to fly back and forth between the NSAC meeting and BNL to coordinate the push for support.
On Tuesday, Jack Sandweiss of the HEPAP arrived for the all-hands meeting, which took place Wednesday in Berkner. Meanwhile, back on Lake Cayuga, NSAC members were wrapping up their meeting. The final report contained words calling for a heavy ion collider. “We identify a relativistic heavy ion collider as the highest priority for the next major facility to be constructed, with the potential of addressing a new scientific frontier of fundamental importance.”
By Thursday, Samios had appointed a “Task Force on Relativistic Heavy Ion Physics” to meet on Friday. That first meeting inaugurated the official effort to build a Heavy Ion Collider, which would lead, within a year, to a formal proposal.
But that is only the beginning of another story.