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| MOCP01 | Beam intensity upgrade at Fermilab | proton, target, antiproton, extraction | 34 | ||
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| TUAX02 | Coherent Instabilities at the Fermilab Booster | impedance, vacuum, dipole, injection | 69 | ||
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Fermilab booster is a fast cycling synchrotron operating on 15 Hz. To exclude problem of eddy currents excited in the vacuum chamber by fast changing magnetic field Booster does not have a conventional vacuum chamber. Instead, the vacuum chamber is formed by poles of the laminated combined function magnets. The exposed magnet laminations result in large transverse and longitudinal impedances affecting both the transverse and longitudinal stability of the beam. Presently, the transverse instability is suppressed by large chromaticity negatively affecting the dynamic aperture and the beam lifetime. Earlier attempts to stabilize the instability by transverse feedback system were unsuccessful. Recently we performed experimental studies to find out the reason. We observed that at reduced chromaticity at injection the most unstable mode is the multibunch high order head-tail mode with growth time of about 12 turns. It develops at synchro-betatron tune with very small fractional part where the transverse impedance is at a maximum. Analytical calculations and numerical simulations verify the observations and allowed us to compute the value of transverse impedance. Another persistent probl
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Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U. S. Dept. of Energy. |
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| TUAY02 | End-to-end beam dynamics for CERN Linac4 | linac, emittance, rfq, quadrupole | 79 | ||
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LINAC 4 is a normal conducting H- linac which aims to intensify the proton flux available for the CERN accelerator complex. This injector is designed to accelerate a 65 mA beam of H- ions up to 160 MeV for injection into the CERN Proton Synchrotron Booster. The acceleration is done in three stages : up to 3 MeV with a Radio Frequency Quadrupole (the IPHI RFQ) operating at at 352 MHz, then continued to 90 MeV with drift-tube structures at 352 MHz (conventional Alvarez and Cell Coupled Drift Tube Linac) and, finally, with a Side Coupled Linac at 700MHz. The accelerator is completed by a chopper line at 3 MeV and a transport and matching line to the PS booster. After the overall layout was determined based on general consideration of beam dynamics and RF, a global optimisation based on end-to-end simulation has refined some design choices. The results and lessons learned from the end-to-end simulations are reported in this paper.
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| WEAX06 | Measurements and Synergia simulations of emittance dilution at the Fermilab Booster. | simulation, resonance, injection, space-charge | 236 | ||
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We present a study of the beam evolution in the Fermilab Booster operating both under nominal conditions and in the vicinity of the sum resonance for different beam currents. We simultaneously recorded the horizontal and vertical beam profiles using the Ion Profile Monitor and beam current. Our analysis extracted 2-D emittances and beam shape information from the IPM data. We compare the results with Synergia simulations including 3-D space charge and higher-order optics to analyze and interpret the experimental results.
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| WEBX04 | Measurement strategy for the CERN Linac4 Chopper-line | linac, rfq, quadrupole, simulation | 262 | ||
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Linac4 is a new accelerator under study at CERN. It is designed to accelerate H- ions to 160 MeV of energy, for injection into the existing Proton Synchrotron Booster. The low energy section, comprising an H- ion source, a 352 MHz Radio Frequency Quadrupole and a 3 MeV chopper line will be assembled at CERN in the next years. Linac 4 is also designed as an injector for the SPL, a high power proton driver delivering 5MW at 3.5 GeV. In this case the beam losses must be limited to 1 W/m and therefore the formation of transverse and longitudinal halo at low energy becomes a critical issue which has to be measured and controlled. The chopper-line is composed of 11 quadrupoles, 3 bunchers and the chopper itself. Its beam dynamics will be characterized with specific detectors and diagnostic lines. In particular the transverse and longitudinal halo will be measured by a Beam Shape and Halo Monitor (BSHM) with a sensitivity of 10.000 particles per bunch and a time resolution of 2ns. In this paper we present the simulation work in preparation for the measurement campaign scheduled in 2008.
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| THAY02 | Progress in slip stacking and barrier-RF | injection, target, antiproton, simulation | 293 | ||
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Slip stacking for pbar production has been operational since December 2004 and increased the beam intensity on pbar target more than 60%. We plan to use slip stacking for NuMI neutrino experiment for effectively increasing intensity to NuMI target by about a factor two in a 2.2 sec MI cycle. In parallel with slip stacking, we plan to study fast momentum stacking using barrier buckets. One barrier rf system has been installed and tested, and second system is being installed during the current shutdown.
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