Reduction of beam-beam synchrobetatron resonances using compensating interaction regions
The next generation of high luminosity circular electron-positron colliders requires many intense bunches in each beam, of order 200 to 1100. The interbunch spacing dictates that two separated rings are necessary. The ensuing problem is how to design the interaction regions so that the two beams can be made to collide and separate using physically realizable magnets, providing low detector background, having a practical vacuum system design, and obeying the constrains of the beam-beam interaction. One of the solutions involves the use of a finite crossing angle between the trajectories of the two beams at the interaction point (IP). The problem with a crossing angle is the well-known problem of synchro-betatron resonances driven by the beam-beam force. A solution to the synchro-betatron problem is to make the beams effectively collide head-on by adding a tilt to each bunch at the IP, a so-called crab crossing. There are several methods to produce these tilted bunches. However, all of these solutions involve placing rf cavities near the interaction region where either the betatron or dispersion functions are large. These crab cavities in turn generate additional design problems. Some of the problems are: a significantly larger impendance of the ring vacuum system, the large cavity voltages, the rotation of both beams, and the control and stability of these cavities. An alternative solution discussed here has two interaction regions physically adjacent to each other where the beams collide at a finite crossing angle without tilted bunches. To ameliorate the synchro-betatron resonances, there is a specially chosen betatron phase advance between the two IRs so that the coupling effects from the beam-beam forces cancel. The consequence of this arrangement is that the interaction region design is now straightforward. 5 refs.
- Research Organization:
- Stanford Linear Accelerator Center, Menlo Park, CA (USA)
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 7050725
- Report Number(s):
- SLAC-PUB-5289; CONF-9002128-1; ON: DE90013586; TRN: 90-023095
- Resource Relation:
- Conference: Workshop on beam dynamics issues of high luminosity asymmetric collider rings, Berkeley, CA (USA), 12-16 Feb 1990
- Country of Publication:
- United States
- Language:
- English
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