On a quasi-isochronous B Factory in the PEP tunnel

Isochronous, or quasi-isochronous storage rings with very small momentum compaction factor α for various applications are discussed. This approach looks very promising for the B-Factory design. A small momentum compaction factor reduces the bunch length at the given RF voltage. A small bunch length allows, in principle, reduction of the beta function at the interaction point (IP) with a corresponding increase of the luminosity. However, achieving this is not easy due to difficulties with local chromatic effects at the IP, more severe background problems in the detector, and enhanced adverse effects of the beam-beam interaction. Although these problems can be addressed, they require substantial changes in the present design. It is worth noting that shorter bunches would also have larger energy losses and larger energy spread, due to wake field excitation and the smaller disruption parameter reducing the enhancement factor. But energy losses scale with the bunch length σz as σz-1/2, remaining small compared with the losses due to synchrotron radiation. The disruption parameter is small in the present design anyway; hence, these effects do not cause additional problems