BNL, Upton, Long Island, New York
After the last successful RHIC Au-Au run in 2004 (Run-4), RHIC experiments now require significantly enhanced luminosity to study very rare events in heavy ion collisions. RHIC has demonstrated its capability to operate routinely above its design average luminosity per store of 2x1026 cm-2 s-1. In Run-4 we already achieved 2.5 times the design luminosity in RHIC. This luminosity was achieved with only 40% of bunches filled, and with β* = 1 m. However, the goal is to reach 4 times the design luminosity, 8x1026 cm-2 s-1, by reducing the beta* value and increasing the number of bunches to the accelerator maximum of 111. In addition, the average time in store should be increased by a factor of 1.1 to about 60% of calendar time. We present an overview of the changes that increased the instantaneous luminosity and luminosity lifetime, raised the reliability, and improved the operational efficiency of RHIC Au-Au operations during Run-7.
BNL, Upton, Long Island, New York
ITEP, Moscow
The Relativistic Heavy Ion Collider~(RHIC) as the first high energy polarized proton collider was designed to provide polarized proton collisions at a maximum beam energy of 250GeV. It has been providing collisions at a beam energy of 100GeV since 2001. Equipped with two full Siberian snakes in each ring, polarization is preserved during the acceleration from injection to 100GeV with careful control of the betatron tunes and the vertical orbit distortions. However, the intrinsic spin resonances beyond 100GeV are about a factor of two stronger than those below 100GeV making it important to examine the impact of these strong intrinsic spin resonances on polarization survival and the tolerance for vertical orbit distortions. Polarized protons were accelerated to the record energy of 250GeV in RHIC with a polarization of 45\% measured at top energy in 2006. The polarization measurement as a function of beam energy also shows some polarization loss around 136GeV, the first strong intrinsic resonance above 100GeV. This paper presents the results and discusses the sensitivity of the polarization survival to orbit distortions.
BNL, Upton, Long Island, New York
We present conceptual design of the NSLS-II injection system. The injection system consists of low-energy linac, booster and transport lines. We review the requirements on the injection system imposed by the storage ring design and means of meeting these requirements. We discuss main parameters and layout of the injection system components.
Fermilab, Batavia, Illinois
BNL, Upton, Long Island, New York
The technique for H- charge exchange for multi-turn injection utilizing stripping foils in the energy range of a few hundred MeV has been used at many labs for decades and most recently up to 1 GeV at the SNS. Utilization the beam from the proposed Proton Driver* would permit the extension of this technique up to 8 GeV. The injection layout and required accelerator modifications are discussed. Results from transverse and longitudinal simulations are presented.
* W. G. Foster and J. A. MacLachlan, "A Multi-mission 8 GeV Injector Linac as a Fermilab Booster Replacement", Proc. Of LINAC-2002, Gyeongju, Korea, p.86.
BNL, Upton, Long Island, New York
To achieve the RHIC polarized proton enhanced luminosity goal of 150*1030 cm-2 sec-1 on average in stores at 250 GeV, the luminosity needs to be increased by a factor of 3 compared to what was achieved in 2006. Since the number of bunches is already at its maximum of 111, limited by the injection kickers and the experiments' time resolution, the luminosity can only be increased by either increasing the bunch intensity and/or reducing the beam emittance. This leads to a larger beam-beam tuneshift parameter. Operation during 2006 has shown that the beam-beam interaction is already dominating the luminosity lifetime. To overcome this limitation, a near-integer working point is under study. We will present recent results of these studies.
BNL, Upton, Long Island, New York
The beam-beam interaction has a significant impact on the beam emittance growth and the luminosity lifetime in RHIC. A simulation study of the emittance growth was performed using the Lifetrac code. The operational conditions of RHIC 2006 100GeV polarized proton run were used in the study. In this paper, the result of this study is presented and compared to the experimental measurements.
BNL, Upton, Long Island, New York
The existence of multipolar components in the dipole and quadrupole magnets is one of the factors limiting the beam stability in the RHIC operations. So, a realistic non-linear model is crucial for understanding the beam behavior and to achieve the ultimate performance in RHIC. A procedure is developed to build a non-linear model using the available multipolar component data obtained from measurements of RHIC magnets. We first discuss the measurements performed at different stages of manufacturing of the magnets in relation to their current state in RHIC. We then describe the procedure to implement these measurement data into tracking models, including the implementation of the multipole feed down effect due to the beam orbit offset from the magnet center. Finally, the field quality analysis in the RHIC interaction regions is presented.
BNL, Upton, Long Island, New York
To further improve the the polarized proton (pp) luminosity in the Relativistic Heavy Ion Collider, the beta functions at the two interaction points (IPs) will be reduced from 1.0 m to 0.9m in 2007. In addition, it is planned to increase the bunch intensity from 1.5*1011 to 2.0*1011. To accommodate these changes, the nonlinear chromaticities and the third resonance driving term should be corrected. In 2007, the number of the arc sextupole power supplies will be doubled from 12 to 24, which allows nonlinear chromaticity correction. With the updated field errors in the interaction regions (IRs), detailed dynamic aperture studies are carried out to optimize the nonlinear correction schemes, and increase the available tune space in collision.