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| MOCP02 | High-power accelerators in China: status and outlook | linac, target, proton, injection | 39 | ||
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High intensity accelerator research is a relatively new subject in China. Recent program includes the accelerator-driven sub-critical power generation and the Beijing Spallation Neutron Source (BSNS) project. The Beijing Spallation Neutron Source (BSNS) is a newly approved project based on a H- linear accelerator and a rapid cycling synchrotron. During the past year, several major revisions were made on the design including the type of the front end, the linac frequency, the transport layout, the ring lattice, and the type of ring components. Possible upgrade paths were also laid out: based on an extension of the warm linac, the ring injection energy and the beam current could be raised doubling the beam power on target to reach 200 kW; an extension with a superconducting RF linac of similar length could raise the beam power near 0.5 MW. Based on these considerations, research and development activities are started. In this paper, we discuss the rationale of design revisions and summarize the recent works.
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| MOCP04 | LHC Upgrade Options and CARE-HHH Activities | luminosity, electron, simulation, quadrupole | 49 | ||
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The European Accelerator Network on High Energy High Intensity Hadron Beams (CARE HHH) is developing scenarios for luminosity and energy upgrades of the Large Hadron Collider (LHC). The LHC upgrade options under consideration differ in terms of beam parameters, electron-cloud effects, beam-beam compensation, use of crab cavities, and interaction-region layout. Complementary investigations concern injector upgrades, novel magnet technologies, advanced collimation schemes, and ultimate intensity limitations. Flanking these upgrade studies, an accelerator-physics code web repository has been set up, and an extensive simulation-code benchmarking campaign is being prepared.
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| TUAX02 | Coherent Instabilities at the Fermilab Booster | impedance, vacuum, booster, 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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| TUAX05 | Studies of e-cloud build up for the FNAL main injector and for the LHC | electron, simulation, cryogenics, injection | 102 | ||
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We present a summary of recent simulation studies of the electron-cloud (EC) build-up for the FNAL Main Injector and for the LHC. In the first case we pay particular attention to the dependence on bunch intensity (Nb) at injection energy, and we focus on the dipole magnets and field-free regions. The saturated value of the average EC density shows a clear threshold in Nb beyond which the beam will be approximately neutralized on average. For the case of the LHC we limit our discussion to arc dipoles at collision energy, and bunch spacings tb=25 ns or tb=75 ns. The main variables exercised in this study are Nb and the peak value of the secondary emission yield (dmax). For tb=25 ns we conclude that the EC power deposition is comfortably below the available cooling capacity of the cryogenic system if dmax is below ~1.2 at nominal Nb. For tb=75 ns, the EC power deposition is insignificant. As a byproduct of this exercise, we reach a detailed understanding of the significant role played by the backscattered secondary electrons.
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| TUBX06 | Betatron Tune Shift due to Nonlinear Resistive-Wall Wake Field | emittance, damping, impedance, betatron | 159 | ||
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I present formulae for the coherent and incoherent tune shifts of a single bunch traveling between two parallel resistive plates. It is shown that for the parameters of an LHC prototype collimator in the SPS, both the nonlinear wake-field components, calculated by Piwinski, and the correct time dependence, e.g., as derived by Burov and Lebedev, must be taken into account.
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| TUBY04 | Operational flexibility of the SPL as proton driver for neutrino and other applications | linac, proton, target, factory | 150 | ||
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The pulse structure of proton linacs is determined by the linac energy, the RF system, and the maximum duty cycle of the source. Short bursts of protons in the microsecond range can be achieved by adding an accumulator ring and a reduction of the bunch length to the order of nanoseconds can be accomplished with an additional bunch compressor ring. The size of the rings along with their RF frequency determines the time structure of the proton driver output burst to hit the target. This pulse structure can be further modified using multiple fillings of the accumulator and compressor rings within one linac pulse. This paper illustrates the possible modes of operation of the SPL at CERN along with its limitations at various energies in combination with accumulator and compressor rings.
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| WEAX05 | Space-Charge Beam Physics Research at the University of Maryland Electron Ring (UMER)* | space-charge, quadrupole, injection, lattice | 218 | ||
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The University of Maryland electron ring (UMER) is a low-energy, high current recirculator for beam physics research with relevance to any applications that rely on intense beams of high quality. We review the space-charge physics issues, experimental and computational investigations, which are currently being conducted at the UMER facility. The physics issues cover a broad range, but we focus on transverse beam dynamics: halo formation, strongly asymmetric beams, Montague resonances, equipartitioning, etc. Furthermore, we report on recent developments in experiments, simulations, and improved diagnostics for space-charge dominated beams.
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| WEAZ04 | Beam-Induced Damage to the Tevatron Components and What Has Been Done About It | controls, vacuum, kicker, proton | 205 | ||
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The Tevatron collimators and magnets were damaged and two thirds of the superconducting ring were quenched on December 5, 2003, induced by a failure in the CDF Roman Pot detector positioning at the end of a 2-TeV proton-antiproton colliding beam store. Analysis of a failure in the abort kicker AC distribution, and detailed modeling of a misbehaved beam dynamics, induced energy deposition and ablation process in the collimator material, have provided a good understanding of the event. The improvements to the detectors, Tevatron quench protection and beam loss monitor systems to avoid such an accident in the future are described.
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| THAY06 | Fast-Pulsed Superconducting Magnets | ion, synchrotron, antiproton, quadrupole | 324 | ||
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Up to now only one synchrotron (Nuclotron at JINR, Dubna) has been equipped with fast-pulsed superconducting magnets. The demand for high beam intensities leads to the requirement of fast-pulsed, periodically cycling magnets for synchrotrons and fast-pulsed magnets for storage rings. An example is FAIR (Facility for Antiproton and Ion Research) at GSI, which will consist of two synchrotrons in one tunnel and several storage rings. The fast field ramp rate and repetition frequency introduce many magnet design problems and constraints in the operation of the accelerator. Persistent currents in the superconductor and eddy currents in wire, cable, iron and vacuum chamber reduce the field quality and generate cryogenic losses. A magnet lifetime of 20 years is anticipated, resulting in up to 108 magnet cycles. Therefore special attention has to be paid to magnet material fatigue problems. R&D work is being done in collaboration with many institutions, to reach the requirements mentioned above. Model dipoles were built and tested. The results of the R&D are reported. The advantages of the use of low field, fast pulsed superconducting, compared to resistive, magnets will be discussed.
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