摘要:

During stores, the beam‐beam interaction has a significant impact on the beam and luminosity lifetimes in RHIC. This was observed in heavy ion, and even more pronounced in proton collisions. Observations include measurements of beam‐beam induced tune shifts, lifetime and emittance growth measurements with and without beam‐beam interaction, and background rates as a function of tunes. In addition, RHIC is currently the only hadron collider in which strong‐strong beam‐beam effects can be seen. Coherent beam‐beam modes were observed, and suppressed by tune changes. In this article we summarize the most important beam‐beam observations made during stores so far. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638361

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The beam‐beam performance of PEP‐II has been monitored by parasitic measurements recorded during routine physics running, and by a few dedicated accelerator physics experiments. These measurements indicate that in some cases, the beam‐beam interaction and the electron‐cloud‐induced blowup of the low‐energy positron beam are somehow coupled and enhance each other. Tailoring the bunch pattern to carefully balance these effects has proven very effective in maximizing the integrated luminosity. The comparison of recent simulation results with experimental data is encouraging. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638362

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

KEK B factory (KEKB) achieved the luminosity of 1034cm−2s−1with a finite crossing angle scheme. The crossing angle made easy the design of the interaction region for a narrow bunch spacing, with the result that it gave a gain of high collision repetition. The crossing angle did not degrade the beam‐beam performance up to the beam‐beam parameter of &xgr; ≈ 0.05. We review the beam‐beam effect of KEKB as a successive case of collision with finite crossing angle. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638363

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

By colliding bunches of greater length under a larger angle, the tune spread caused by the beam‐beam interaction can be reduced. Assuming a constant limit for the beam‐beam tune shift, the bunch intensity can then be raised. In this way, a luminosity increase is possible. We review this strategy for proton beams in RHIC, with two collisions and consider six long bunches. Barrier cavities are used to fill every accelerating bucket of the machine, except for an abort gap, and to create the superbunches bunches at store. Resonances driven by the beam‐beam interaction and coherent effects are neglected in this article. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638364

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Long‐range beam‐beam interactions in Run II at the Tevatron are the dominant sources of beam loss and lifetime limitations of anti‐protons, especially at injection energy. I discuss observations and theoretical understanding of these beam‐beam effects. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638365

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The two RHIC rings have independent rf systems to accommodate different species. Thus, the radio frequencies can differ when the phase and radial loops are closed, and the rf frequencies of the two rings are not synchronized. A radio frequency difference leads to longitudinally moving beam crossing points. When the crossing points are between the beam splitting dipoles, the beams experience the beam‐beam interaction. Outside the interaction region the beam‐beam interaction is switched off. In this way the tune is modulated. A computation of the tune modulation depth, pulse shape and frequency is presented. Tune modulation measurements are shown. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638366

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We discuss the original idea of beam‐beam compensation (BBC) in Section I, sequence of events in 2001–2002 and use of the Tevatron Electron Beam (TEL) for DC beam removal in Section II, (anti)proton lifetime improvement in Section III, experimental data on the BBC attempts in Section IV and, conclusively, Section V is devoted to discussion on important phenomena, needed improvements and future plans. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638367

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Long range beam‐beam effects play an important role in the Tevatron. Active compensation is envisaged by current wires, as proposed recently for the LHC. Here, we present the first steps in this program, namely the principle of the compensation, the derivation of the transfer map of the wire, potentially increasing robustness by utilizing wire cages, and some very preliminary results of application to the Tevatron at injection energy. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638368

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

In cases of multi‐bunches operation in storage‐ring colliders, serious long‐range beam‐beam effects could be due to many parasitic collisions that are localized inside interaction regions or/and distributed around the ring. To reduce the long‐range beam‐beam effects, the compensation of long‐range beam‐beam interaction with magnetic multipole correctors based on minimizations of nonlinearities in one‐turn or sectional maps of a collider has been proposed. With LHC as a test model, the effectiveness of the multipole compensation of long‐range beam‐beam interactions was studied in terms of improvement of dynamic aperture and reduction of emittance growth. The study showed that both the local and global compensation of long‐range beam‐beam interactions with magnetic multipole correctors is very effective in increasing the dynamic aperture and improving the linearity of the phase‐space region relevant to the beams. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638369

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Beam‐beam interaction with four‐beam scheme and beam‐beam compensation is studied with computer simulations. The modes, phase space structures, and feasibility of bunch‐by‐bunch feedback system for coherent dipole motions with beam‐beam interactions are discussed with four‐beam scheme and beam‐beam compensation. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1638370

出版商:AIP    

年代:1903

数据来源: AIP