English: The Michigan Mark I FFAG accelerator (fixed field alternating gradient accelerator), as erected at the University of Michigan before it was moved to the Midwestern Universities Research Association lab in Madison, Wisconsin. This 400KeV electron accelerator was the first operational FFAG accelerator. As shown here, it used betatron acceleration; after the move to Madison, it was reconfigured as a 500KeV electron synchrotron.

The horizontal ring centered in the photo was composed of alternating positive (big) and negative (small) bending magnets. These enclosed the vacuum chamber that accommodated particle orbits between 0.7 and 1.0m diameter. Magnet power was provided by one of the two motor-generator sets partially visible in the upper left. The large rectangular yoke on the right of the photo is the water-cooled betatron core, a transformer core where the secondary winding was the particle beam being accelerated. The primary winding on the betatron core was excited by 500Hz AC provided by the other motor generator set. A bank of large capacitors, not visible, was wired across the betatron primary winding improve the power factor.

The vacuum pump for the accelerator filled most of the under-table space visible in the photo. The large rectangular box in the upper left was an electronics rack, partially obscuring the view of the motor generator sets and an oscilloscope.