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
We are presenting the layout and the optics of a beam line to be used as a medical gantry in radiation therapy. The optical properties of the gantry’s beam line are such as to make the beam line achromatic and uncoupled. These two properties make the beam spot size, which is delivered and focused by the gantry, on the tumor of the patient, independent of the angular orientation of the gantry. In this paper we present the layout of the magnetic elements of the gantry, and also present the theoretical basis for the optics design of such a gantry.
* N. Tsoupas et. al. “Uncoupled achromatic tilted S-bend” Presented at the 11th Biennial European Particle Accelerator Conference, Genoa, Italy, June 23-27,2008
BNL, Upton, Long Island, New York, USA
To reduce the effect of trajectory perturbations due to vibrations of the final focusing quadrupoles at RHIC, global orbit feedback was successfully prototyped during run-10. The system was tested using transfer functions between the beam position monitors and correctors obtained from the online optical model and a correction algorithm based on singular value decomposition (SVD). In run-11 we plan to self-calibrate the system using SVD matrices derived from orbit response matrix (ORM) measurements acquired real-time using the new FPGA-based signal processing. Comparisons between measurement and model and of feedback performance with the two methods are presented.
BNL, Upton, Long Island, New York, USA
Vibrations of the cryogenic triplet magnets at the Relativistic Heavy Ion Collider (RHIC) are suspected to be causing the beam perturbations observed at frequencies around 10 Hz. Several solutions to counteract the effect have been considered in the past, including reinforcing the magnet base support assembly, a mechanical servo feedback system, and a local beam feedback system at each of the two experimental areas. However, implementation of the mechanical solutions would be expensive, and the local feedback system was insufficient since perturbation amplitudes outside the experimental areas were still problematic. A global 10 Hz orbit feedback system is currently under development at RHIC consisting of 36 beam position monitors (BPMs) and 12 small dedicated dipole corrector magnets in each of the two counter-rotating rings. A subset of the system consisting of 8 BPMs and 4 corrector magnets in each ring was installed and successfully tested during the RHIC 2010 run; and the complete system is being installed for the 2011 run. A description of the overall system architecture and results with beam will be discussed.
BNL, Upton, Long Island, New York, USA
As part of the search for a phase transition or critical point on the QCD phase diagram, an energy scan including 5 different energy settings was performed during the 2010 RHIC heavy ion run. While the top beam energy for heavy ions is at 100 GeV/n and the lowest achieved energy setpoint was significantly below RHICs injection energy of approximately 10 GeV/n, we also provided beams for data taking in a medium energy range above injection energy and below top beam energy. This paper reviews RHIC experience and challenges for RHIC medium energy operations that produced full experimental data sets at beam energies of 31.2 GeV/n and 19.5 GeV/n.
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.