Tantalus Recieves Its Place In History

As the thirty year anniversary of the use of Synchrotron Radiation (SR) at SRC for research approaches, a cornerstone of this technology, the Tantalus electron storage ring, is to become a Smithsonian National Museum of American History exhibit. The 240 MeV ring, which is less than a mile from Aladdin, has been used only sparingly since 1987 when the 1 GeV Aladdin facility was fully opened to research.

Ed Rowe stands in front of the birthplace of SR research, the Tantalus Electron Storage Ring.

The story of the storage ring begins with the Midwestern University Research Association’s (MURA) curiosity with particle accelerators. MURA had planned to build a large (12.5 GeV) proton accelerator in the field across from the current Physical Sciences Laboratory, but in 1964 that project fell through. In early 1965 the research group began another project to continue fundamental studies of particle accelerators. This project would include the construction of a small (240 MeV) electron storage ring.

During that same year, The National Academy of Science formed a subcommittee on the use of synchrotron radiation for condensed matter research chaired by Professor Frederick C. Brown of the University of Illinois. The subcommittee learned of the storage ring project and knew that electron storage rings would emit SR during operation. In March of 1966, the two organizations agreed to cooperate in the construction to achieve their different, but related goals.

During the next two years, the structure of the scientific community that MURA had created drastically changed. Particle accelerator research funds became scarce, and in 1967 the University of Wisconsin- Madison absorbed the research center and created the Physical Sciences Laboratory (PSL). Although many of the scientists from MURA continued working, the mission of the organization changed. The Physical Sciences Laboratory was to be a service organization for UW-Madison, providing scientific and engineering research to programs on campus. The budget for PSL did not include completing the construction of the electron storage ring, so the scientists chose to name their incomplete machine Tantalus, in reference to the Greek King who was punished with thirst and hunger in view of unreachable water and fruit.

To survive, the Tantalus project had to be adapted to the ever growing and changing scientific interests of the time. By late 1967 several SR research scientists had substantial investments in the Tantalus project and funding was found to complete the first ever dedicated synchrotron radiation source. In early 1968 the ring was complete, and in August of that year, the first data was collected by Dr. Ulrich Gerhardt. By 1973, Tantalus had become an operational extension of the University of Wisconsin-Madison providing a SR research facility that produced more than 100 journal articles a year, a substantial feat for those days considering there were only four beamlines in operation until 1974.

As interest for SR research grew, the demand for a “brighter light bulb”, as current Associate Director Ed Rowe says, by far exceeded the supply. In 1977 construction of the much larger Aladdin electron storage ring began and as the new facility prepared for its first users in 1983, the Synchrotron Radiation Center separated from PSL.

Although Tantalus continued to be available for research while Aladdin was brought up to full capacity in 1987, researchers lost interest in Tantalus as both beam energy, current, and reliability in the Aladdin ring grew. Research on the Tantalus ring was discontinued at the beginning of 1987 and in late 1993, it became apparent that Tantalus would be decommissioned and dismantled. This was not a satisfactory end to the project, in the opinion of the first SRC director, Ed Rowe.

Rowe wanted to save the machine where SR research had started, so he contacted the Smithsonian National Museum of American History about their interest in acquiring this piece of history. Dr. Paul Forman, the curator for the Electricity and Modern Physics Collection at the museum responded to Rowe’s inquiry. Dr. Forman thought the project sounded interesting, so the two of them began the task of convincing the museum’s acquisition committee of the historical importance of Tantalus. After gathering evidence, it was clear to both Dr. Forman and the committee that this was truly a piece of history worth saving. “Not only was the machine a true innovation in electron storage ring use, but it was an ideal size for an exhibit,” Dr. Forman summarized. “ Most accelerator research projects of this quality are much too large for display.”

Dr. Forman visited SRC in April and got a chance to see the storage ring operate, maybe for its last time. It has not yet been determined when or how this piece of history is to be displayed, but Dr. Forman hopes to have one half of the 3 meter ring, including the RF cavity, dismantled and shipped to the Smithsonian some time this fall.

When asked when Tantalus would go on display, Dr. Forman said, “this exhibit, like most exhibits, is for posterity’s benefit and will not be displayed for some time”. Although scientists who use SR radiation may consider Tantalus history already, one must consider that the current displays include the telegraph and the first telephone invented by Alexander Graham Bell. These pieces were saved for over one hundred years before attaining “historical” status in the eyes of the Smithsonian. While in storage, Tantalus will share quarters with such distinguished innovations as the Carnegie Van de Graaff Accelerator and Ed McMillan’s Electron Synchrotron, until the proper time comes for public display.