• J.G. Alessi, D.S. Barton, E.N. Beebe, S. Bellavia, O. Gould, A. Kponou, R.F. Lambiase, E.T. Lessard, V. LoDestro, R. Lockey, M. Mapes, D.R. McCafferty, A. McNerney, M. Okamura, A. Pendzick, D. Phillips, A.I. Pikin, D. Raparia, J. Ritter, J. Scaduto, L. Snydstrup, M. Wilinski, A. Zaltsman
  BNL, Upton, Long Island, New York
• T. Kanesue
  Kyushu University, Hakozaki
• U. Ratzinger, A. Schempp, J.S. Schmidt, M. Vossberg
  IAP, Frankfurt am Main

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

A new heavy ion preinjector, consisting of an Electron Beam Ion Source (EBIS), an RFQ, and IH Linac, is under construction at Brookhaven National Laboratory. This preinjector will provide ions of any species at an energy of 2 MeV/u, resulting in increased capabilities for the Relativistic Heavy Ion Collider, and the NASA Space Radiation Laboratory programs. Initial operation of the EBIS and RFQ will be reported on, along with the status of the construction and installation of the remainder of the preinjector.

• H. Hahn, S. Bellavia, I. Ben-Zvi, E. M. Choi
  BNL, Upton, Long Island, New York

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.

A 56 MHz Superconducting RF cavity is developed for the luminosity enhancement of the Relativistic Heavy Ion Collider (RHIC). The 56 MHz SRF cavity enables to adiabatically rebucket the beam from the 28 MHz accelerating cavities, which with shorter bunch lengths will enhance the luminosity significantly. The 56 MHz SRF cavity fundamental mode must be damped during injection and acceleration by a fundamental mode damper (FD), which is physically withdrawn at store for operation. The cavity frequency changes from the withdrawing motion but is kept below the beam frequency at store by a judicious axial placement of the FD. Physics studies by numerical simulations, tests of the FD in the prototype cavity, and the challenging engineering issues are here addressed. In addition, higher-order mode (HOM) dampers are necessary for the stable operation of the 56 MHz SRF cavity. The HOM’s are identified and the external Q factors are obtained from tests of the prototype cavity and are compared to simulations with the CST MWS program. The HOM damper blocks the fundamental mode by a 5 element high pass filter. The HOM stability criteria of the cavity are satisfied with four HOM dampers.

• T. Tsang, S. Bellavia, R. Connolly, D.M. Gassner, Y. Makdisi, M.G. Minty, T. Russo, P. Thieberger, D. Trbojevic, A. Zelenski
  BNL, Upton, Long Island, New York

A gas fluorescence beam profile monitor has been realized at the relativistic heavy ion collider (RHIC) using the polarized atomic hydrogen gas jet. RHIC proton beam profiles in the vertical plane are obtained as well as measurements of the width of the gas jet in the beam direction. For gold ion beams, the fluorescence cross section is sufficiently large so that profiles can be obtained from the residual gas alone, albeit with long light integration times and lower number of Au ions than protons. We estimate the fluorescence cross-section of 100 GeV protons and Au ions on hydrogen gas to be 6.6x10-21 cm² ~1.7x10-16 cm², respectively*. We calculate the beam emittance to provide an independent measurement of the RHIC beam. This optical beam diagnostic technique, utilizing the beam induced fluorescence from injected or residual gas, represents a step towards the realization of a simple and truly noninvasive beam monitor for high-energy particle beams together with a wall-current-monitor system and/or a low light level optical temporal measurement system, a 3-dimensional particle beam profile system can be envisioned providing routine diagnosis of high-energy particle beams.

*T. Tsang, et. al., Rev. Sci. Instrum. 79, 105103 (2008).