EPAC08 - List of Authors (Fischer, W.)

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Fischer, W.

Paper	Title	Page
MOPC106	Injection and Acceleration of Au³¹⁺ in the BNL AGS	313
	W. Fischer, L. Ahrens, K. A. Brown, C. J. Gardner, J. W. Glenn, H. Huang, M. Mapes, J. Morris, V. Schoefer, L. Smart, P. Thieberger, N. Tsoupas, K. L. Unger, K. Zeno, S. Y. Zhang BNL, Upton, Long Island, New York C. Omet, P. J. Spiller GSI, Darmstadt
	Injection and acceleration of ions in a lower charge state reduces space charge effects, and, if further electron stripping is needed, may allow elimination of a stripping stage and the associated beam losses. The former is of interest to the accelerators of the GSI FAIR complex, the latter for BNL RHIC collider operation at energies lower than the current injection energy. Lower charge state ions, however, have a higher likelihood of electron stripping which can lead to dynamic pressures rises and subsequent beam losses. We report on experiments in the AGS where Au³¹⁺ ions were injected and accelerated instead of the normally used Au⁷⁷⁺ ions. Beam intensities and the average pressure in the AGS ring are recorded, and compared with calculations for dynamic pressures and beam losses. The experimental results will be used to benchmark the STRAHLSIM dynamic vacuum code and will be incorporated in the GSI FAIR SIS100 design.
TUPP035	Analysis of Intensity Instability Threshold at Transition in RHIC	1616
	W. Fischer, I. Blackler, M. Blaskiewicz, P. Cameron, C. Montag, V. Ptitsyn, T. Roser BNL, Upton, Long Island, New York
	The beam intensity of ion beams in RHIC is limited by a fast transverse instability at transition, driven by the machine impedance and electron clouds. For gold and deuteron beams we analyze the dependence of the instability threshold on beam and machine parameters from recent operational data and dedicated experiments. We fit the machine impedance to the experimental data.
WEPP001	Energy Loss of Coasting Gold Ions and Deutrons in RHIC	2518
	N. P. Abreu, M. Blaskiewicz, K. A. Brown, J. J. Butler, W. Fischer, M. Harvey, S. Tepikian BNL, Upton, Long Island, New York H. Burkhardt CERN, Geneva
	The total energy loss of coasting gold ion beams was measured at RHIC at two energies, corresponding to a gamma of 75.2 and 107.4. We describe the experiment and observations and compare the measured total energy loss with expectations from ionization losses at the residual gas, the energy loss due to impedance and synchrotron radiation. We find that the measured energy losses are below what is expected from free space synchrotron radiation. We believe that this shows evidence for suppression of synchrotron radiation which is cut off at long wavelength by the presence of the conducting beam pipe.
WEPP002	The Effect of Head-on Beam-beam Compensation on the Stochastic Boundaries and Particle Diffusion in RHIC	2521
	N. P. Abreu, W. Fischer, Y. Luo, G. Robert-Demolaize BNL, Upton, Long Island, New York
	To compensate the effects from the head-on beam-beam interactions in the polarized proton operation in the Relativistic Heavy Ion Collider (RHIC), an electron lens (e-lens) is proposed to collide head-on with the proton beam. We used an extended version of SixTrack for multiparticle beam-beam simulation in order to study the effect of the e-lens on the stochastic boundary and also on diffusion. The stochastic boundary was analyzed using Lypunov exponents and the diffusion was characterized as the average rms spread of the action after 10⁴ turns. For both studies the simulations were performed with and without the e-lens and with full and partial compensation.
WEPP018	Operational Experience with a Near-integer Working Point at RHIC	2563
	C. Montag, M. Bai, J. Beebe-Wang, W. Fischer, Y. Luo, N. Malitsky, T. Roser, T. Satogata, S. Tepikian BNL, Upton, Long Island, New York
	During the RHIC polarized proton run in FY 2006 it became evident that the luminosity performance is limited by the beam-beam effect. With a working point between 2/3 and 7/10, and the necessity to mirror the tunes of the two RHIC rings at the diagonal, the beam with a horizontal tune closest to 2/3 showed poor lifetime. To overcome this limitation, a near-integer working point has been proposed. Tracking studies performed at both working points showed a larger dynamic aperture near the integer tune than above 2/3. In Run-8, this new working point was commissioned in one ring of RHIC, while the other ring was operated at the same working point as in Run-6. In this paper we report the commissioning process and operational experience with this new working point.
WEPP011	Setup and Performance of RHIC for the 2008 Run with Deuteron and Gold Collisions	2548
	C. J. Gardner, N. P. Abreu, L. Ahrens, J. G. Alessi, M. Bai, D. S. Barton, J. Beebe-Wang, M. Blaskiewicz, J. M. Brennan, K. A. Brown, D. Bruno, J. J. Butler, P. Cameron, C. Carlson, R. Connolly, T. D'Ottavio, A. J. Della Penna, K. A. Drees, W. Fischer, W. Fu, G. Ganetis, J. W. Glenn, M. Harvey, T. Hayes, H. Huang, P. F. Ingrassia, J. Kewisch, R. C. Lee, V. Litvinenko, Y. Luo, W. W. MacKay, M. Mapes, G. J. Marr, A. Marusic, R. J. Michnoff, C. Montag, J. Morris, B. Oerter, F. C. Pilat, E. Pozdeyev, V. Ptitsyn, G. Robert-Demolaize, T. Roser, T. Russo, P. Sampson, J. Sandberg, T. Satogata, C. Schultheiss, F. Severino, K. Smith, D. Steski, S. Tepikian, R. Than, P. Thieberger, D. Trbojevic, N. Tsoupas, J. E. Tuozzolo, A. Zaltsman, K. Zeno, S. Y. Zhang BNL, Upton, Long Island, New York
	This year deuterons and gold ions were collided in the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) for the first time since 2003. The setup and performance of the collider for this run is reviewed with a focus on improvements that have led to an order of magnitude increase in luminosity since the 2003 run.
WEPP019	RHIC Polarized Proton Performance in Run-8	2566
	C. Montag, N. P. Abreu, L. Ahrens, M. Bai, D. S. Barton, A. Bazilevsky, J. Beebe-Wang, M. Blaskiewicz, J. M. Brennan, K. A. Brown, D. Bruno, G. Bunce, R. Calaga, P. Cameron, R. Connolly, T. D'Ottavio, K. A. Drees, A. V. Fedotov, W. Fischer, G. Ganetis, C. J. Gardner, J. W. Glenn, T. Hayes, H. Huang, P. F. Ingrassia, A. Kayran, J. Kewisch, R. C. Lee, V. Litvinenko, A. U. Luccio, Y. Luo, W. W. MacKay, Y. Makdisi, N. Malitsky, G. J. Marr, A. Marusic, R. J. Michnoff, J. Morris, B. Oerter, H. Okada, F. C. Pilat, P. H. Pile, G. Robert-Demolaize, T. Roser, T. Russo, T. Satogata, C. Schultheiss, M. Sivertz, K. Smith, S. Tepikian, D. Trbojevic, N. Tsoupas, J. E. Tuozzolo, A. Zaltsman, A. Zelenski, K. Zeno, S. Y. Zhang BNL, Upton, Long Island, New York
	During Run-8, the Relativistic Heavy Ion Collider (RHIC) provided collisions of spin-polarized proton beams at two interaction regions. Helical spin rotators at these two interaction regions were used to control the spin orientation of both beams at the collision points. Physics data were taken with different orientations of the beam polarization. We present recent developments and improvements as well as the luminosity and polarization performance achieved during Run-8.
THPC059	Studies of Wire Compensation and Beam-beam Interaction in RHIC	3119
	H. J. Kim, T. Sen Fermilab, Batavia, Illinois N. P. Abreu, W. Fischer BNL, Upton, Long Island, New York
	Beam-beam interaction is one of the dominant source of emittance growth and luminosity lifetime deterioration. A current carrying wire has been proposed to compensate long-range beam-beam effects in the LHC and the principle is now being experimentally investigated at RHIC. In this paper, we use simulations to study the effectiveness of wire compensation based on tune footprints, diffusive apertures, and beam loss rates using a parallel weak-strong beam simulation code (BBSIM). In addition we extensively study the diffusion properties of RHIC beams for different beam and wire parameters. Beam-beam effects on emittance growth are investigated through the solution of the diffusion equation for the transverse action variables.
THPC062	Multi-Particle Weak-Strong Simulations of RHIC Head-on Beam-Beam Compensation	3125
	Y. Luo, N. P. Abreu, W. Fischer, G. Robert-Demolaize BNL, Upton, Long Island, New York
	An electron beam has been proposed in the Relativistic Heavy Ion Collider (RHIC) to compensate beam-beam effects in polarized proton collisions. This electron beam will collide head-on with the proton beam. Using the weak-strong beam-beam interaction model, we have carried out six-dimensional multiparticle simulations to investigate the effects of head-on beam-beam compensation. Beam lifetime, transverse emittances, and luminosity are calculated for cases with and without beam-beam compensation for up to 10 million turns. The migrations of particles between different actions and the beam spectrum are also calculated.
THPC082	Wire Excitation Experiments in the CERN SPS	3176
	U. Dorda, J.-P. Koutchouk, R. Tomas, J. Wenninger, F. Zimmermann CERN, Geneva R. Calaga, W. Fischer BNL, Upton, Long Island, New York
	In order to study the effect of long range interaction and its wire compensation experimentally, current carrying wires are installed in the CERN Super Proton Synchrotron (SPS). In this paper we summarize the main results of the 2007 wire excitation results at 26, 37 and 55 GeV including wire-current-, beam-wire distance and chromaticity scans. A strong dependence on the chromaticity and indications of a threshold effect at 37 and 55 GeV was found. The results are compared to simulation, to a simple analytic scaling law and to experimental results from RHIC. Wire-driven resonances have been observed through the Fourier spectrum of experimental BPM data and compared to simulations.