SURF´s up at NBS: A Progress Report

The NBS Synchrotron UV Radiation Facility (SURF-II) is a 250 MeV single-magnet, weak-focusing electron storage ring, with 10 MeV microtron injector. Circulating beams of up to 35 mA at energies up to 250 MeV have been achieved. Beam lifetime, limited by Touschek effect, is extended to several hours by resonant vertical rf excitation. At low energies bunch shape oscillations occur, involving coherent synchrotron oscillations, negative-mass-type blowup and loss of beam. Effective avoidance and suppression techniques are discussed. A new set of high current gradient correction coils and power supplies, plus additional pancakes for the main field coils are being obtained. These are expected to extend SURF operation to 280 MeV and provide useful light output to 0.4 keV photon energies.