BNL, Upton, Long Island, New York, USA
RHIC operation as the polarized proton collider presents unique challenges since both luminosity and spin polarization are important. With longitudinally polarized beams at the experiments, the figure of merit is LP4. A lot of upgrades and modifications have been made since last polarized proton operation. A 9 MHz rf system has been installed to improve longitudinal match at injection and to increase luminosity. The beam dumps were upgraded to allow for increased bunch intensities. A vertical survey of RHIC was performed before the run to get better magnet alignment. The orbit control has also been improved this year. Additional efforts were put in to improve source polarization and AGS polarization transfer efficiency. To preserve polarization on the ramp, a new working point was chosen such that the vertical tune is near a third order resonance. The overview of the changes and the operation results are presented in this paper.
BNL, Upton, Long Island, New York, USA
MEPhI, Moscow, Russia
IUCF, Bloomington, Indiana, USA
A new polarimeter for absolute proton beam polarization measurements at 200 MeV to accuracy better than ±0.5% has been developed as a part of the RHIC polarized source upgrade. The polarimeter is based on the elastic proton-carbon scattering at 16.2 degree angle, where the analyzing power is close to 100% and was measured with high accuracy. The elastically and in-elastically scattered protons are clearly identified by the difference in the propagation through variable copper absorber and energy deposition of the protons in the detectors. The 16.2 degree elastic scattering polarimeter was used for calibration of a high rate inclusive 12 degree polarimeter for the on-line polarization tuning and monitoring. This technique can be used for accurate polarization measurements in energy range of at least 160-250 MeV.
BNL, Upton, Long Island, New York, USA
After reconfiguration of the low energy (35 keV) and the medium energy (750 keV) transport lines in 2009-10, the Brookhaven linac is now delivering the highest intensity beam since it was built in 1970 (~120 μA average current of H− to the Brookhaven Linac Isotope Producer). It is also now delivering lower emittance polarized H− ion beam for the polarized program at RHIC. To increase the intensity further, we are replacing the buncher in the 750 keV line with one with higher Q value, to allow operation at higher power. Also, to improve polarization, we are replacing the magnetic solenoid before the RFQ in the 35 keV line by a solenoid-einzel lens combination. The paper will report on the results of these changes.
BNL, Upton, Long Island, New York, USA
As the worlds’s first high energy polarized proton col- lider, RHIC has made significant progresses in measuring the proton spin structure in the past decade. In order to have better understanding of the contribution of u quark and d quark to the proton spin structure, collisions of high energy polarized neutron beams are required. In this paper, we discuss the perspectives of accelerating polarized light ions, like deuteron, Helium-3 and tritium. We also repre- sent simulation studies of accelerating polarized Helium-3 in RHIC.
Brookhaven National Lab., Upton, NY 11973
BNL, Upton, Long Island, New York, USA
BINP SB RAS, Novosibirsk, Russia
Basic limitations on the high-intensity H− ion beam production were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na- vapor jet ionizer cell. These studies are the part of the polarized source upgrade (to 10 mA peak current and 85% polarization) project for RHIC. In the source the atomic hydrogen beam of a 3-5 keV energy and total (equivalent) current up to 5 A is produced by neutralization of proton beam in pulsed hydrogen gas target. Formation of the proton beam (from the surface of the plasma emitter with a low transverse ion temperature ~0.2 eV) is produced by four-electrode spherical multi-aperture ion-optical system with geometrical focusing. The hydrogen atomic beam intensity up to 1.0 A /cm2 (equivalent) was obtained in the Na-jet ionizer aperture of a 2.0 cm diameter. At the first stage of the experiment H− beam with 36 mA current, 5 keV energy and ~1.0 cm-mrad normalized emittance was obtained using the flat grids and magnetic focusing. The experimental results of the high-intensity neutral hydrogen beam generation and studies of the charge-exchange polarization processes of this intense beam will be presented.
BNL, Upton, Long Island, New York, USA
FRIB, East Lansing, Michigan, USA
MIT, Middleton, Massachusetts, USA
We present the design of future high-energy high-luminosity electron-hadron collider at RHIC called eRHIC. We plan on adding 20 (potentially 30) GeV energy recovery linacs to accelerate and to collide polarized and unpolarized electrons with hadrons in RHIC. The center-of-mass energy of eRHIC will range from 30 to 200 GeV. The luminosity exceeding 1034 cm-2 s-1 can be achieved in eRHIC using the low-beta interaction region with a 10 mrad crab crossing. We report on the progress of important eRHIC R&D such as the high-current polarized electron source, the coherent electron cooling and the compact magnets for recirculating passes. A natural staging scenario of step-by-step increases of the electron beam energy by builiding-up of eRHIC's SRF linacs and a potential of adding polarized positrons are also presented.
BNL, Upton, Long Island, New York, USA
The RHIC polarized proton physics program requires high luminosity and high polarization which depends directly on the intensity, emittances and polarization delivered to RHIC by the injector chain. In the AGS, two partial snakes create gaps in the realized spin-tune around the integers which allows an accelerating beam with sufficiently small vertical emittance and near-integer vertical tune to avoid the imperfection and vertical intrinsic resonances. The same strategy strengthens the many (82) weak horizontal intrinsic resonances crossed during AGS acceleration. A system speeding up these resonance crossings – the AGS JumpQuad system: 82 tiny (0.04) fast (100usec) betatron tune shifts – has been commissioned and evolved during RHIC Runs 09, 10, and 11. Subtle properties of the AGS geometry and lattice, magnified into relevance by the high vertical tune can result in polarization-damaging emittance growth when combined with the Jump Quad gymnastics. Orbit stability is critical. Some aspects of the JumpQuad system, of this commissioning effort and related developments will be described.