Current bearing wire compensators were successfully used in the 2005-2006 run of the DA{Phi}NE collider to mitigate the detrimental effects of parasitic beam-beam interactions. A marked improvement of the positron beam lifetime was observed in machin
e operation with the KLOE detector. In view of the possible application of wire beam-beam compensators for the High Luminosity LHC upgrade, we revisit the DA{Phi}NE experiments. We use an improved model of the accelerator with the goal to validate the modern simulation tools and provide valuable input for the LHC upgrade project.
Recently the peak luminosity achieved on the DA{Phi}NE collider has been improved by almost a factor three by implementing a novel collision scheme based on large Piwinski angle and Crab-Waist. This encouraging result opened new perspectives for phys
ics research and a new run with the KLOE-2 detector has been scheduled to start by spring 2010. The KLOE-2 installation is a complex operation requiring a careful design effort and a several months long shutdown. The high luminosity interaction region has been deeply revised in order to take into account the effect on the beam caused by the solenoidal field of the experimental detector and to ensure background rejection. The shutdown has been also used to implement several other modifications aimed at improving beam dynamics: the wiggler poles have been displaced from the magnet axis in order to cancel high order terms in the field, the feedback systems have been equipped with stronger power supplies and more efficient kickers and electrodes have been inserted inside the wiggler and the dipole vacuum chambers, in the positron ring, to avoid the e-cloud formation. A low level RF feedback has been added to the cavity control in both rings.
An innovatory interaction region has been recently conceived and realized on the Frascati DA{Phi}NE lepton collider. The concept of tight focusing and small crossing angle adopted until now to achieve high luminosity in multibunch collisions has evol
ved towards enhanced beam focusing at the interaction point with large horizontal crossing angle, thanks to a new compensation mechanism for the beam-beam resonances. The novel configuration has been tested with a small detector without solenoidal field yielding a remarkable improvement in terms of peak as well as integrated luminosity. The high luminosity interaction region has now been modified to host a large detector with a strong solenoidal field which significantly perturbs the beam optics introducing new design challenges in terms of interaction region optics design, beam transverse coupling control and beam stay clear requirements
Long-range beam-beam interactions (parasitic crossings) were one of the main luminosity performance limitations for the lepton F-factory DAFNE in its original configuration. In particular, the parasitic crossings led to a substantial lifetime reducti
on of both beams in collision. This puts a limit on the maximum storable current and, as a consequence, on the achievable peak and integrated luminosity. In order to mitigate the problem, numerical and experimental studies of the parasitic crossings compensation by current-carrying wires have been done. During the operation for the KLOE experiment two such wires have been installed at both ends of the interaction region. They produced a relevant improvement in the lifetime of the weak beam (positrons) at the maximum current of the strong one (electrons) without luminosity loss, in agreement with the numerical predictions. The same compensating mechanism has been adopted during the run for the FINUDA experiment as well, with less evident benefits than in the previous case. The interplay between nonlinearities originating from the beam-beam interaction and the ring lattice has been studied by theoretical simulation and experimental measurements. Compensation procedures have been set up relying on the electromagnetic octupoles installed on both rings and used in addition to wire compensation. In this paper the parasitic crossings effects in the DAFNE interaction regions and their compensation by wires and octupoles are described. A detailed theoretical analysis of the interplay about different non-linearities is presented; eventually experimental measurements and observations are discussed.
DAFNE, the Frascati F-factory, has recently completed experimental runs for the three main detectors, KLOE, FINUDA and DEAR achieving 1.6x10E+32 cm-2s-1 peak and 10 pb-1 daily integrated luminosities. Improving these results by a significant factor r
equires changing the collision scheme. For this reason, in view of the SIDDHARTA detector installation, relevant modifications of the machine have been realized, aimed at implementing a new collision scheme based on a large Piwinski angle and crab-waist, together with several other hardware modifications involving injection kickers, bellows and beam pipe sections.
