• H.-C. Hseuh, L. Doom, M.J. Ferreira, C. Longo, V. Ravindranath, P. Settepani, S. Sharma, K. Wilson
  BNL, Upton, Long Island, New York

Funding: Work performed under the auspices of U.S. Department of Energy, under contract DE-AC02-98CH10886

National Synchrotron Light Source II is a 3-GeV, 792-meter circumference, high-flux and high-brightness synchrotron radiation facility being constructed at Brookhaven National Laboratory. The storage ring vacuum chambers are made of extruded aluminium and the bending magnet photons are intercepted at discrete photon absorbers. The design of the storage ring vacuum system will be presented, with emphasis on vacuum chamber design and fabrication, pumping arrangements, photon beam tracking and absorber positioning, and interface with other accelerator systems. The evaluation of the aluminium chamber prototypes and RF shielded bellows will also be described.

• A. Blednykh, M.J. Ferreira, S. Krinsky
  BNL, Upton, Long Island, New York

Impedance of two vacuum chamber components, Bellows and BPM, is considered in some detail. In order to avoid generation of Higher-Order Modes (HOM’s) in the NSLS-II bellows, we designed a new low-impedance RF shielding consisting of 6 wide and 2 narrow metal plates without opening slots between them. The short-range wakepotential has been optimized taking into account vertical offset of RF fingers from their nominal position. The results were compared with data of bellows designed at other laboratories. Narrow-band impedance of the BPM Button has been studied. TE-modes in the BPM button were suppressed by a factor of 8 by modification of existing housings. Two new types of housings are shown. The total impedance of the NSLS-II storage ring is discussed in terms of the loss factor and the vertical kick factor for a 3mm-Gaussian bunch.