BNL, Upton, Long Island, New York, USA
In the presence of an effective coherent electron cooling, the rms ion bunch length in eRHIC will be kept at 8.4cm, which is about a factor of 3 shorter than the current RHIC rms bunch length. Together with a factor of 2 increase in bunch intensity, coherent instabilities could be a potential limitation for achieving desired machine performance. In this study, we use the tracking code TRANFT to find thresholds and growth rates for various single bunch and coupled bunch instabilities with linear chromaticity and amplitude dependent tune shift taken into account. Based on the simulation results, requirements of machine parameters such as rf voltage, linear chromaticity, and octupole strength are specified to avoid these instabilities.
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
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 kink instability is one of the major beam dynamics issues of the linac-ring based electron ion collider. This head-tail type instability arises from the oscillation of the electron beam inside the opposing ion beam. It must be suppressed to achieve the desired luminosity. There are various ways to suppress the instability, such as tuning the chromaticity in the ion ring or by a dedicated feedback system of the electron beam position at IP, etc. However, each method has its own limitation. In this paper, we will discuss an alternative opportunity of suppressing the kink instability of the proposed eRHIC at BNL using the existing pickup-kicker system of the stochastic cooling system in RHIC.
BNL, Upton, Long Island, New York, USA
In polarized proton operation, the RHIC performance is limited by the head-on beam-beam effect. To overcome these limitations two electron lenses are under construction. We give an overview of the progress over the last year. Guns, collectors and the warm electron beam transport solenoids with their associated power supplies have been constructed. The superconducting solenoids that guide the electron beam during the interaction with the proton beam are near completion. A test stand has been set up to verify the performance of gun, collector and some of the instrumentation. The RHIC infrastructure is being prepared for installation, and simulations continue to optimize the performance.
BNL, Upton, Long Island, New York, USA
Stochastic cooling is used in the Relativistic Heavy Ion Collider to increase the integrated luminosity of ion collisions by a factor of two. The cooling system has been assembled incrementally over the past several years, starting with longitudinal cooling only, then adding cooling in the vertical planes, and recently completed with cooling systems in all three phase space planes of both rings. The system operates from 6 to 9 GHz in the longitudinal planes and from 4.7 to 7.8 GHz in the transverse planes, yielding a cooling rate that overcomes Intra-Beam Scattering at the beginning of a store and reaches equilibrium with a factor of 2 reduction of emittances. The system’s components and mode of operation will be presented along with measurements of the beam parameters during stores with stochastic cooling in operation.
BNL, Upton, Long Island, New York, USA
Proton bunch intensities in RHIC will be increased from 2*1011 to 3*1011 protons per bunch to increase the luminosity, together with head-on beam-beam compensation using electron lenses. To study the feasibility of the intensity increase, beam experiments are being performed. Recent experimental results will be presented.
BNL, Upton, Long Island, New York, USA
* V. Balbekov, PRSTAB, 14, 094401 (2011).
** M. Blaskiewicz, PRSTAB 1, 044201 (1998).
BNL, Upton, Long Island, New York, USA
Over the last few years, physicists have suspected the presence of noise acting on the RHIC beams observable as occasional emittance growth at high beam energies. While the noise was sporadic in the past, it became more persistent during the run-11 setup period. An investigation diagnosed the source as originating from the RHIC abort kicker system. Once identified the issue was quickly resolved. We report in this paper the investigation result, circuit analysis, measured and simulated waveforms, solutions, and future plans.