BNL, Upton, Long Island, New York, USA
The head-on beam-beam interaction is the dominant luminosity limiting effect in polarized proton operation in RHIC. To mitigate this effect two electron lenses were installed in the two RHIC rings. We summarize the hardware and electron beam commissioning results to date, and report on the first experience with the electron-hadron beam interaction. In 2014 RHIC is operating with gold beams only. In this case the luminosity is not limited by head-on beam-beam interactions and compensation is not necessary. The goals of this year’s commissioning efforts are a test of all instrumentation; the demonstration of electron and gold beam overlap; the demonstration of electron beam parameters that are sufficiently stable to have no negative impact on the gold beam lifetime; and the measurement of the tune footprint compression from the beam overlap. With these demonstrations, and a lattice with a phase advance that has a multiple of 180 degrees between the beam-beam interaction and electron lens locations, head-on beam-beam compensation can be commissioned in the following year with proton beams.
BNL, Upton, Long Island, New York, USA
After running uranium-uranium and copper-gold collisions in 2012, the high energy heavy ion run of the Relativistic Heavy Ion Collider (RHIC) for Fiscal Year 14 (Run14) is back to gold-gold (Au-Au) collisions at 100 GeV/nucleon. Following the level of performance achieved in Run12, RHIC is still looking to push both instantaneous and integrated luminosity goals. To that end, a new 56 MHz superconducting RF cavity was installed and commissioned, designed to keep ions in one RF bucket and improve luminosity by allowing a smaller beta function at the interaction point (IP) due to a reduced hourglass effect. The following presents an overview of these changes and reviews the performance of the collider.
BNL, Upton, Long Island, New York, USA
TIT, Yokohama, Japan
RLNR, Tokyo, Japan
A new laser ion source (LIS) for low charge state ion production was installed on RHIC-EBIS. This is the first LIS to be combined with an Electron Beam Ion Source (EBIS) type heavy ion source. The LIS provides intense low charge state ions from any solid state material, with low emittance and narrow pulse length. These features make it suitable as an external source of 1+ ions that can be injected into the EBIS trap for charge breeding. In addition, a LIS is the only type ion source which can allow rapid switching among many ion species, even on pulse-by-pulse basis, by changing either laser path or target position, to strike the material of choice. The EBIS works as a charge breeder, with the extracted high charge state ions used in the following accelerators. The beams from LIS will be used for RHIC and NASA Space Radiation Laboratory (NSRL) at BNL. The rapid beam switching, which was not possible with existing ion sources, will expand the research field at NSRL as a galactic cosmic ray simulator. The results of commissioning will be shown.