摘要:

©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301870

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Features of beam stability for the 50 Hz, 800 MeV, ISIS proton synchrotron are described. The issues discussed include the following: longitudinal coasting beam, longitudinal bunched beam, transverse coasting beam, transverse head-tail bunched beam, and the absence of the electron-proton instability. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301871

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

For the last few years the Brookhaven AGS has operated at record proton intensities. This high beam intensity allowed for the simultaneous operation of several high precision rare kaon decay experiments. The record beam intensities were achieved after the AGS Booster was commissioned and a transition jump system, a powerful transverse damper, and an rf upgrade in the AGS were completed. The intensity is presently limited by space charge effects at both Booster and AGS injection and transverse instabilities in the AGS. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301872

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Fermilab has started the design work of a high intensity proton source called the proton driver. It would provide a 4 MW proton beam to the target for muon production. This paper discusses the basic features of this machine and the associated accelerator physics and design issues. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301873

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We shortly review electron cloud effects in the CERN Large Hadron Collider. In particular, we discuss recent simulations showing a significant reduction of the beam induced heat load on the cold beam screen with weak satellite bunches at 5 ns from the main proton bunches. This can be an effective solution to shorten the conditioning period required to lower the secondary electron yield of the screen surface. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301874

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Some stability issues of low-energy intense beams are discussed. These include inductor tuners for the cancellation of the longitudinal space-charge induced potential-well distortion and their consequences, transient beamloading and possible feed-forward alleviation, coherent and incoherent transverse tune shifts, as well as the impact of transverse space charge on transverse mode-coupling instability. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301875

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The future use of the CERN SPS accelerator as injector for the Large Hadron Collider, LHC, and the possible use of the SPS as a neutrino source for the Gran Sasso experiment are pushing the maximum intensity requirements of the accelerator much higher than achieved up to now. At the same time the requirements on beam quality are becoming far more stringent. The SPS machine, built in the 70’s, is not a “smooth” machine. It contains many discontinuities in vacuum chamber cross-section and many cavity-like objects, as well as the 5 separate RF systems at present installed. All these lead to a high impedance, seen by the beam, spread over a wide frequency range. As a result there is a constant fight against instabilities, both single and multi bunch, as the intensity increases. A program of studies is under way in the SPS to identify, reduce, and remove where possible the sources of these impedances. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301876

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301877

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We present results from experiments at the GSI machines as well as computer simulation for space charge dominated coasting beams (below transition). It is found that for the high-current machines presently under discussion the actual challenge lies in the nonlinear regime. Experiments are in good agreement with theory and simulation in the linear regime; for the nonlinear regime and long-time evolution rsp. saturation our experimental results show good agreement in some aspects, like wave steepening. To analyze the final momentum distribution we still depend on simulation, which shows that the behavior differs substantially, depending on whether the working point in the impedance plane lies close to the real (resistive dominated) or imaginary (space charge dominated) axis, or in between. For the space-charge-dominated regime(Re&hthinsp;Z≪Im&hthinsp;Z)it is found by computer simulation that for currents far above the Keil-Schnell threshold self-stabilization occurs by formation of a momentum tail, hence linear instability criteria can be practically ignored. It is shown here that the global impedance distribution is of crucial importance. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301878

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The vacuum chamber and other elements surrounding particle beams in high-energy particle accelerators or storage rings constituteimpedances. They often lead to limitations of beam current by coherent instabilities or to energy loss which may overheat some of the elements. To control these limitations it is necessary to understand and minimize the impedances of the various structures surrounding the beam. For simple geometries analytic expressions can be derived which permit their estimation and scaling. For more complicated elements, powerful computer codes are nowadays available to obtain impedances or wake potentials. However, the results depend critically on the exact shape and dimensions of the structures and thus cannot be predicted in general. Therefore this presentation concentrates on three specific topics which were discussed recently: the resistive wall effect in non-circular chambers, the impedance of thin metal layers on ceramic beam pipes and that of wire cages used for rf shielding. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1301879

出版商:AIP    

年代:1999

数据来源: AIP