BNL, Upton, Long Island, New York, USA
As the world’s first high energy polarized proton collider, RHIC has made significant progress in measuring the proton spin structure in the past decade. In order to have better understanding of the contribution of up and down quarks to the proton spin structure, collisions of high energy polarized neutron beams are required. In this paper, we present studies of accelerating polarized Helium-3 in RHIC with the current dual snake configuration. The possibilities of adding two more pairs of snakes for accelerating polarized He-3 were explored. Results of a six snake configuration in RHIC are also reported in the paper.
BNL, Upton, Long Island, New York, USA
In this article we calculate and compare the off-momentum dynamic aperture for lattices with different phase advances per FODO cell in the RHIC heavy ion runs. A lattice with an increased phase advance was adopted in 2008-2011 to reduce transverse emittance growth rates from intra-beam scattering. However, during these runs, a large beam loss was observed with longitudinal RF re-bucketing which increased the momentum spread. With operational transverse stochastic cooling in the 2011 RHIC heavy ion run, the transverse intra-beam scattering emittance growth was eliminated, and the beam loss during stores was determined by the off-momentum aperture and burn-off from luminosity. We investigate the possibilities to increase the off-momentum dynamic aperture that would lead to an increase in the integrated luminosity.
BNL, Upton, Long Island, New York, USA
BNL, Upton, Long Island, New York, USA
BNL, Upton, Long Island, New York, USA
In polarized proton operation in RHIC coherent beam-beam modes are routinely observed with beam transfer function measurements in the vertical plane. With the existence of coherent modes a larger space is required in the tune diagram than without them and stable conditions can be compromised for operation with high intensity beams as foreseen for future luminosity upgrades. We report on experiments and simulations carried out to understand the existence of coherent modes in the vertical plane and their absence in the horizontal plane, and investigate possible mitigation strategies.
BNL, Upton, Long Island, New York, USA
In this article we will present the measurement and correction of the off-momentum β*-beat in the RHIC proton run. The beta-beat will be measured with the AC dipole and by shifting RF frequency. We will focus on the correction of the off-momentum beta-beat at the interaction points IP6 and IP8 with the arc chromatic sextupole families. The effects of the off-momentum beta-beat correction on the global chromaticities and dynamic aperture will be estimated through beam experiments and the numerical simulation.
BNL, Upton, Long Island, New York, USA
BNL, Upton, Long Island, New York, USA
CERN, Geneva, Switzerland
The further improvement of RHIC luminosity performance requires more precise understanding of the RHIC modeling. Hence, it is necessary to minimize the beta-beat, deviation of measured beta function from the calculated beta functions based on an model. The correction of beta-beat also opens up the possibility of exploring operating RHIC polarized protons at a working point near integer, a preferred choice for both luminosity as well as beam polarization. The segment-by-segment technique for reducing beta-beat demonstrated in the LHC operation for reducing the beta-beat was first tested in RHIC during its polarized proton operation in 2011. It was then fully implemented during the RHIC polarized proton operation in 2012. This paper reports the commissioning results. Future plan is also presented.
BNL, Upton, Long Island, New York, USA
The five ac dipole design of RHIC spin flipper in the Blue ring was first commissioned during the RHIC 2012 polarized proton operation. The advantage of this design is to eliminate the vertical coherent betatron oscillations outside the spin flipper*. Spin flipping efficiency was measured with both 100 GeV and 250 GeV polarized proton beams. This paper presents the latest commissioning results.
* M. Bai , T. Roser, C. Dawson, Y. Makdisi, W. Meng, F. Meot, P. Oddo, C. Pai, P. Pile, RHIC Spin Flipper New Design and Commissioning Plan, IPAC10 proceedings, IPAC 2010, Kyoto, Japan, 2010
Tech-X, Boulder, Colorado, USA
BNL, Upton, Long Island, New York, USA
We are performing several experiments during the RHIC ramp to better understand the impact of orbit errors on the polarization at our current working point. These will be conducted by exciting specified orbit harmonics during the final two large intrinsic resonance crossing in RHIC during the 250 GeV polarized proton ramp. The resultant polarization response will then be measured.
BNL, Upton, Long Island, New York, USA
The high energy (T=250 GeV) polarized proton beam experiments performed in RHIC, require high polarization of the beam. In order to preserve the polarization of the proton beam, during the acceleration in the AGS, which is the pre-injector to RHIC, two partial helical magnets* have been installed in AGS. In order to minimize the loss of the beam polarization due to the various intrinsic spin resonances occurring during the proton acceleration, we constrain the value of the vertical tune to be higher than 8.97. With the AGS running at near integer tune the perturbations caused by the partial helical magnets is large resulting in large beta and dispersion waves. To mitigate the adverse effect of the partial helices on the optics of the AGS, we have introduced compensation quads** in AGS. In this paper we present the beam optics of the AGS which ameliorates this effect of the partial helices.
* H. Huang, et al., Proc. EPAC06, p. 273, (2006).
** N. Tsoupas et al., Proc. PAC07, p. 3723 (2007).