Description and history
G.I. Budker at the INP in Novosibirsk proposed in 1966 that the phase space of an ion beam orbiting in a storage ring can be reduced with a co-moving electron beam of matched velocity. By the 1980’s this principle of ‘cooling’ was in use for storing anti-protons at CERN and FNAL.
Robert Pollock at IUCF recognized that this new technology could benefit nuclear physics research. The new experimental environment featured an intense stored beam circulating through a thin internal target. A proposal to build such a machine at IUCF to explore this new environment was approved by the NSF for 6.6 M$, starting February 1983.
The necessary building addition was completed in 1985 and in April 1988 the first cooled beam was orbiting in the ring. The construction involved about 50 people.
The Cooler storage ring featured an RF cavity to accelerate a stored proton beam to 500 MeV, i.e., beyond the pion production threshold in nucleon-nucleon collisions. In fact, for a while, the highest-energy electron-cooled beam in the world circulated in the Indiana Cooler.
Beam from the cyclotron was injected into the Cooler on a time-share basis with other experiments. Vertically polarized proton and deuteron beams were available. An arrangement of longitudinal magnetic field solenoids, a so-called Siberian snake, made non-vertical beam polarization possible. The first demonstration of such a scheme was accomplished with the Cooler in 1989.
Internal targets included solid targets (with limitations), gas jet targets and polarized atoms injected into ‘storage cells’ (open tubes around the beam to increase target density).
A new ion source and a Cooler injection synchrotron (CIS) were commissioned in 2000, making the Cooler independent of the cyclotron. With this addition, the Cooler reached its peak performance with about 1.5 mA of polarized proton or deuteron beam stored.
The last beam was orbiting in the ring at the end of July 2002.
The Cooler history is recounted in “The Indiana Cooler”: A Retrospective, Annu. Rev. Nucl. Part. Sci. 57, 1 (2007).