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The DAΦNE Phi-factory upgrade, foreseen for the SIDDHARTA detector run in 2007, requires a new magnetic and mechanical layout to exploit the "large Piwinski angle" and "crab waist" concepts [1]. New permanent quadrupole magnets and aluminium vacuum chamber with thin window have been designed for the new interaction region, with the aim to reuse as...
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Citations
The achievements of the three main e+e- Factories have been impressive. The KEK B-Factory has achieved a peak luminosity of 1.7x1034 cm-2 sec-1 and the PEP-II B- Factory has reached 1.2x1034 cm-2 sec-1 while the DAFNE Phi-Factory has obtained 1.5x1032 cm-2 sec-1. Early in the B-Factory running, CP violation in the B meson system was found to be consistent with the prediction of the Standard Model. Now all three factories are integrating as much luminosity as they can in order to look for rare decay channels that may have a rate that differs from the value predicted by the Standard Model and therefore hint at New Physics. There are two newer factories that have started or are about to start. The Tau-charm factory at CESR has been delivering luminosity to the CLEO detector and BEPCII, the newest Tau-charm e+e- factory located at IHEP in Beijing, has just started commissioning. I will give a status report on the recent accomplishments of all five factories and will show what these facilities have for plans to further improve performance.
DAΦNE, the Frascati Φ-factory, has recently completed experimental runs for the three main detectors, KLOE, FINUDA and DEAR achieving 1.6x10 32 cm -2 s -1 peak and 10 pb -1 daily integrated luminosities. Improving these results by a significant factor requires 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.
The DAΦNE Φ-factory at INFN LNF has been upgraded in the second half of 2007 with a scope to test a recently proposed scheme of crab waist collisions. The vacuum chamber of the collider has been substantially
modified: two new low impedance interaction regions have been designed and installed, the new stripline
injection kickers have been implemented, the old bellows have been substituted by the new ones and almost all ion clearing electrodes removed. In the paper we discuss the low impedance design of these new vacuum chamber components and compare bunch lengthening measurements in the modified DAΦNE with simulation results.
A new Radio Frequency (RF) shielded bellows, using the technology of omega shaped strip of beryllium copper material, has been developed and tested on DAΦNE UPGRADE [1] [6] [7]. The RF omega shield is composed of many Be-Cu strips held by an external floating ring. Thermal power loss on strips can be easily extracted and dissipated allowing high beam current operation. Leakage of beam induced electromagnetic fields through the RF shield is almost suppressed. Twenty omega bellows were manufactured and installed in the DAФNE storage rings and showed good performances up to 1.9A stored current.
An upgrade of the DAΦNE Φ-Factory [1] at LNF is planned in view of the installation of the Siddharta detector [2] in fall 2007. A new Interaction Region suitable to test the large Piwinski angle and crab waist (CW) collision schemes will be installed. Other machine improvements, such as new injection kickers, bellows and
beam pipe layouts will be realized, with the goal of reaching luminosity of the order of 1033/cm2/s. The
principle of operation of the new scheme, together with hardware designs and simulation studies, are presented.
A new interaction region (IR) vacuum chamber has been designed for the DAFNE upgrade aimed at testing of the crabbed waist collision scheme. Compared to the existing IR vacuum chamber, the new one has a simplified design and consists essentially of the confluence of straight tubes, having a double Y shape. Sharp discontinuities have been avoided to limit the beam impedance of the structure. However, the study of the electromagnetic interaction with the beam is necessary in order to avoid excessive power loss due to possible higher order modes (HOM) trapped in the Y-shape chamber. The first design of the chamber has been analyzed with HFSS and HOMs have been found and characterized. On the basis of these results some modifications in the geometry of the IR chamber have been introduced to eliminate or attenuate these trapped resonances. The results of these simulations are presented. New electromagnetic shielding for the bellows inserted in the IR chambers, have been developed as well. The design criteria and the simulation results for these shielded bellows are also reported.
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 reduction 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.
The Frascati Phi-factory DAFNE has successfully completed experimental runs for the three main detectors, KLOE, FINUDA and DEAR. The best peak luminosity achieved so far is 1.6x10^32 cm-2s-1, while the best daily integrated luminosity is 10 pb-1. At present the DAFNE team is preparing an upgrade of the collider based on the novel crab waist collision scheme. The upgrade is aimed at pushing the luminosity towards 10^33 cm-2s-1. In this paper we describe present collider performance and discuss ongoing preparatory work for the upgrade.
