The Synchrotron Radiation Center

The University of Wisconsin-Madison

Tantalus and Ed Rowe

Ednor Rowe stands next to elements of the Tantalus storage ring.

The Synchrotron Radiation Center (SRC) at the University of Wisconsin-Madison was a research facility providing infrared, ultra violet, and soft X-ray light for use in research on a multitude of materials, ranging from high temperature superconductors and computer chips to cancer cells.i It is was the first fully-dedicated multi-user synchrotron light source, and consisted of two electron storage rings: Tantalus, which was used for research through 1987 and decommissioned in the early 1990s and is now housed in the Smithsonian, and Aladdin, which was in use until 2014.

On 13 November 2015, APS President Sam Aronson presented a plaque to UW Vice Chancellor of Research and Graduate Education Marsha Mailick, commemorating almost half a century of SRC contributions and their significance in the history of science. The citation reads: "From 1968 to 2014 the University of Wisconsin-Madison operated the Tantalus and later Aladdin electron storage rings to produce synchrotron radiation for scientific research. Located at the Synchrotron Radiation Center, near Stoughton, WI, Tantalus was the first dedicated synchrotron light source. In 1985 it was replaced by Aladdin, which was used until 2014. Operating for nearly 50 years, the SRC was a birthplace of synchrotron radiation science, hosting thousands of researchers from all over the world and leading to fundamental scientific discoveries."

The history of the SRC dates back to the 1950s when a group of scientists at US universities launched the Midwestern University Research Association (MURA). The 15 institutions that united to form this coalition were dedicated to increasing high-energy physics research in the Midwest region. By 1967, MURA, which was headquartered in Madison, Wisconsin, had accomplished one of its main objectives—it won the bid to build Fermilab in Illinois. MURA officially ended, and many scientists went to Batavia to help design what was to become a leading particle accelerator facility.ii

However, some adventurous physicists remained in Madison and continued their work in other areas of high-energy physics, in particular synchrotron radiation.iii They customized leftover accelerator designs, and in 1968, supported by the Atomic Energy Commission, the group built a small electron particle accelerator.iv “But just as the apparatus neared completion, funding was cut off. Its creators, feeling teased by fate and their government backers, dubbed the machine ‘Tantalus’”v , after the Greek mythological figure who was destined to stand in a pool of water with fruit trees just out of his grasp for all eternity. Despite these challenges, the team succeeded in launching the research facility. This 240 MeV electron storage ring, about the size of a backyard trampoline, became operational in March 1968, and the first synchrotron radiation experiments commenced six months later. Tantalus was the hub of the SRC operated for nearly twenty years, and the user base grew to over 100 scientists worldwide.

Since the machine was optimized to produce synchrotron radiation in the ultraviolet, this spectral region became an early test bed for reflectance, transmission, photoionization and photoemission spectroscopies, as well as the earliest experiments on angle-resolved photoemission spectroscopy. Early studies of insertion devices were also carried out at Tantalus. Although Tantalus operated until 1987, it was superseded by the 1 GeV electron storage ring Aladdin in 1985, which remained in operation until March, 2014. Aladdin extended the SRC spectral range into the soft X-ray region, with an increase in the user base to two hundred and fifty. There was a concomitant explosion in experimental studies at SRC in all areas of synchrotron science. Aladdin incorporated five undulators and twenty-five beamlines, and a vibrant accelerator research and development program that produced a new continuous-wave superconducting radio-frequency gun. SRC also housed a unique IR imaging beamline that accepted radiation from an entire bending magnet, with which IR tomography was demonstrated in 2013.

Both Tantalus and Aladdin were designed and built by teams led by Ed Rowe at the University of Wisconsin Physical Sciences Laboratory. With the formation of SRC when Tantalus became operational, Rowe fostered an environment that became the norm for synchrotron radiation user facilities, since so many users made their first measurements at SRC. “Researchers shared information and the results of their experiments in a collegial environment. There was no ‘King of the Ring’ among these goal-oriented scientists.”vi A focus on the education of the next generation of users had always been at the forefront of the style of research conducted at SRC. And the welcome that Rowe provided to new users, and the helping hands that the SRC staff extended to young scientists, were hallmarks that continued after the laboratory directorship passed into the hands of Dave Huber, Jim Taylor, Franz Himpsel and, most recently, Joe Bisognano.

The history and significance of the SRC and its first ring, Tantalus, live on at the Smithsonian Institute. When research ceased on Tantalus, it became apparent that the ring would be decommissioned and dismantled, but to Rowe this was not a satisfactory end to the project.vii He wanted to save the machine where synchrotron research had started, so he contacted the Smithsonian National Museum of American History about their interest in acquiring this piece of history. Paul Forman, the curator for the Electricity and Modern Physics Collection at the museum 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 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,” Forman summarized. “Most accelerator research projects of this quality are much too large for display.”viii Today, in the Archives Center of the National Museum of American History, Smithsonian Institute, one can find the Tantalus ring and written documentation in the form of operational and data notebooks and logbooks that trace the creation, building, maintenance, and experiments carried out on the machine. There are also black and white photographs, slides, and oral and video documentation.ix

i   About SRC:
ii  History of SRC,
iii History of SRC,
iv  IBID
  Guide to the Tantalus Synchrotron Radiation Source Collection, Smithsonian Institute,
vi  IBID
vii Tantalus Receives its place in history, Aladdin, the quarterly newsletter of the SRC, Summer 1995,
viii IBID
ix  Guide to the Tantalus Synchrotron Radiation Source Collection, Smithsonian Institute,