  The first pre-prototype of a single-coil superconducting miniundulator has
been built and studied. Its basic specifications include 10 main periods and
two end compensation periods, a period length of 7 mm, and a gap of 2 mm. The
design is based on a racetrack-like coil configuration that is subsequently
compressed to form the gap region with the spatially alternating currents
flowing perpendicularly to the electron beam above and below the midplane.
Operation up to an excitation current slightly beyond 400 A before quenching
resulted in a peak magnetic flux density on axis of about 1 T and an undulator
parameter of K about 0.65.
