Development of A Super-Mini Undulator

This paper describes development and initial results for a small prototype superconducting undulator with a period less than 1 cm, referred to here as a “supermini” undulator. The development of superconducting mini-undulators started in the early 1990s with work at BNL and KIT (Germany). In 1998, KIT demonstrated the first photon production with a super-mini of 3.8 mm period length [1]. This super-mini consisted of two coils wound bi-filarly in analogy to a solenoid. If such coils are arranged alongside each other, separated only by a small gap on the order of a couple of millimeters, a spatially alternating magnetic field is produced that makes a passing electron beam undulate and emit undulator radiation. Owing to the short period length, the photon energy is much higher than with conventional undulators at the same electron energy. Likewise, for a given photon energy, the electron energy can be much smaller entailing considerable cost savings of accelerator, building, and operations. PROTOTYPE SUPER-MINI The prototype Super-Mini undulator supports a 7.0 mm period, K factor of 0.72, gap of 2 mm, 10 periods with 2 end periods, and a field of 1.1 T with an expected current density of 1000 A/mm2. The overall length of the prototype device is 80 mm. This device utilizes a unique winding pattern that facilitates the very short period. This sort of device has been called a “singlecoil super-mini”.