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| MOPCH100 | Polarized Proton Acceleration in the AGS with Two Helical Partial Snakes | resonance, polarization, injection, extraction | 273 | ||
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Acceleration of polarized protons in the energy range of 5 to 25 GeV is particularly difficult: the depolarizing resonances are strong enough to cause significant depolarization but full Siberian snakes cause intolerably large orbit excursions and it is not feasible in the AGS since straight sections are too short. Recently, two helical partial snakes with double pitch design have been built and installed in the AGS. With careful setup of optics at injection and along the ramp, this combination can eliminate intrinsic and imperfection depolarizing resonances encountered during acceleration. This paper presents the accelerator setup and preliminary results. The effect of horizontal intrinsic resonances in the presence of two partial snakes are also discussed.
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| MOPCH101 | On the Feasibility of a Spin Decoherence Measurement | polarization, RHIC, synchrotron, proton | 276 | ||
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In this paper, we study the feasibility of making a turn-by-turn spin measurement to extract the spin tune of a synchrotron from a polarized beam injected perpendicular to the stable spin direction. For the ideal case of a zero-emittance beam with no spin-tune spread, there would be no spin decoherence and a measurement of the spin tune could easily be made by collecting turn-indexed polarization data of several million turns. However, in a real beam there is a momentum spread which provides a tune spread. With a coasting beam the tune spread will cause decoherence of the spins resulting in a fast depolarization of the beam in a thousand turns. With synchrotron oscillations the decoherence time can be greatly increased, so that a measurement becomes feasible with summation of the turn-by-turn data from a reasonable number of bunches (100 or fewer). Both the cases of a single Siberian snake and a pair of Siberian snakes are considered.
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| MOPLS024 | RHIC Performance as Polarized Proton Collider in Run-6 | polarization, RHIC, luminosity, emittance | 592 | ||
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The Relativistic Heavy Ion Collider in Run-6 was operating in polarized proton mode. With two Siberian Snakes per ring, the polarized protons were brought into collisions at 100 Gev and 31.2 Gev energies. The control of polarization orientation at STAR and PHENIX experiments was done using helical spin rotators. Physics studies were conducted with longitudinal, vertical and radial beam polarization at collision points. This paper presents the performance of RHIC as a polarized proton collider in the Run-6 with emphasis on beam polarization and luminosity issues.
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| TUPLS125 | Spin Transport from AGS to RHIC with Two Partial Snakes in AGS | RHIC, injection, extraction, dipole | 1795 | ||
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The stable spin direction in the RHIC rings is vertical. With one or two strong helical Siberian snakes in the AGS, the stable spin direction at extraction is not vertical. Interleaved vertical and horizontal bends in the transport line between AGS and the RHIC rings also tend to tip the spin away from the vertical. In order to preserve polarization in RHIC, we examine several options to improve the matching of the stable spin direction during beam transfer from the AGS to each of the RHIC rings. While the matching is not perfect, the most economical method appears to be a lowering of the injection energy by one unit of G*gamma to 45.5.
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| TUPLS133 | Material Irradiation Damage Studies for High Power Accelerators | target, proton, BNL, controls | 1816 | ||
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High-performance targets intercepting multi MW proton beams are the key toward intense muon or neutrino beams. To achieve this goal one must push the envelope of the current knowledge on material science and material endurance and survivability to both short and long proton beam exposure. The demand imposed on the targets of high power accelerators and the limitations of most materials in playing such pivotal roles have led to an extensive search and experimentation with new alloys and composites. These new high-performance materials and composites, which at first glance, appear to possess the right combination of properties satisfying target requirements, are explored under accelerator target conditions where both shock and irradiation damage are at play. Results of the on-going, multi-phased experimental effort under way at BNL involving heavy irradiation of candidate materials using 200 MeV protons at the end of the BNL Linac as well as results on post-irradiation analysis assessing irradiation damage are presented.
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| WEPCH063 | Measurements and Modeling of Eddy Current Effects in BNL's AGS Booster | vacuum, booster, dipole, quadrupole | 2068 | ||
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Recent beam experiments at BNL's AGS Booster have enabled us to study in more detail the effects of eddy currents on the lattice structure and our control over the basic lattice parameters of betatron tune and chromaticity. The Booster is capable of operating at ramp rates as high as 8 T/sec. At these ramp rates eddy currents in the vacuum chambers have significant effects on the fields and gradients seen by the beam as it is accelerated. The Booster was designed with these effects in mind and to help control the field uniformity and linearity in the Booster Dipoles special vacuum chambers were designed with current windings to negate the effect of the induced eddy currents. In this report results from measurements of these effects will be presented. Results from modeling and comparisons to the measurements will also be presented.
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| WEPCH152 | Comment on Healy's Symplectification Algorithm | BNL, CERN, dipole | 2281 | ||
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For long-term tracking, it is important to have symplectic maps for the various electromagnetic elements in an accelerator ring. While many standard elements are handled well by modern tracking programs, new magnet configurations (e.g., a helical dipole with a superimposed solenoid) are being used in real accelerators. Transport matrices and higher terms may be calculated by numerical integration through model-generated or measured field maps. The resulting matrices are most likely not quite symplectic due to numerical errors in the integrators as well as the field maps. In his thesis*, Healy presented a simple algorithm to symplectify a matrix. This paper presents a discussion of limitations of this method.
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*L. M. Healy, "Lie Algebraic Methods for Treating Parameter Errors in Particle Accelerators", Doctoral Thesis. University of Maryland, unpublished (1986). |
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| WEPCH153 | Symplectic Interpolation | coupling, resonance, BNL, dipole | 2284 | ||
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It is important to have symplectic maps for the various electromagnetic elements in an accelerator ring. For some tracking problems we must consider elements which evolve during a ramp. Rather than performing a complicated numerical integration for every turn, it should be possible to integrate the trajectory for a few sets of parameters, and then interpolate the transport map as a function of one or more parameters, such as energy. We present two methods for interpolation of symplectic matrices as a function of parameters: one method is based on the logarithm of the matrix, and the other is based on the related but simpler Healy symplectification method.
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| THPCH026 | Parallel 3-D Space Charge Calculations in the Unified Accelerator Library | space-charge, simulation, synchrotron, instrumentation | 2835 | ||
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The paper presents the integration of the SIMBAD space charge module in the UAL framework. SIMBAD is a Particle-in-Cell (PIC) code. Its 3-D parallel approach features an optimized load balancing scheme based on a genetic algorithm. The UAL framework enhances the SIMBAD standalone version with the interactive ROOT-based analysis environment and an open catalog of accelerator algorithms. The composite package addresses complex high intensity beam dynamics studies and has been developed as a part of the FAIR SIS 100 project.
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| THPCH027 | An Experimental Proposal to Study Heavy-ion Cooling in the AGS due to Beam Gas or the Intrabeam Scattering | ion, electron, scattering, RHIC | 2838 | ||
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Low emittance of not-fully-stripped gold(Z=79) Au+77 Helium-like ion beams from the AGS (Alternating Gradient Synchrotron) could be attributed to the cooling phenomenon due to inelastic intrabeam scattering [1]. The low emittance gold beams have always been observed at injection in the Relativistic Heavy Ion Collider (RHIC). There have been previous attempts to attribute the low emittance to a cooling due to the exchange of energy between ions during the inelastic intrabeam scattering. The Fano-Lichten theory[2] of electron promotion might be applied during inelastic collisions between helium like gold ions in the AGS. During collisions if the ion energy is large enough, a quasi-molecule could be formed, and electron excitation could occur. During de-excitation of electrons, photons are emitted and a loss of total bunch energy could occur. This would lead to smaller beam size. We propose to inject gold ions with two missing electrons into RHIC at injection energy and study the beam behavior with bunched and de-bunched beam, varying the RF voltage and the beam intensity. If the "cooling" is observed additional.
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