INFN/LNF, Frascati (Roma)
Metallic clearing electrodes have been designed to absorb the photo-electrons in the DAΦNE positron ring. They have been inserted in the wigglers and dipoles vacuum chambers and have been connected to external high voltage generators. In the paper we present the design of the devices and the results of the electromagnetic simulations related to both the transfer and longitudinal beam coupling impedances. We also present the results of the RF measurements and the first results with the DAΦNE circulating positron beam.
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
The Super-B asymmetric e+e- collider is designed for 1036 cm-2sec-1 luminosity and beam energies of 6.7 and 4.18 GeV for e+ and e-, respectively. The machine will have the High and Low Energy Rings (HER and LER), and one Interaction Point (IP) with 60 mrad crossing angle. The INFN-LNF at Frascati is one of the proposed sites, and a lattice for short 1.3 km rings fitting to this site has been designed. The two rings are radially separated by 2 m except near the IP and in the dogleg on the opposite side of the rings. The injection sections and RF cavities are included. The lattice is optimized for a low emittance required for the desired high luminosity. Final Focus chromaticity correction is optimized for large transverse and energy acceptance. The "crab waist" sextupoles are included for suppression of betatron resonances induced at the IP collisions with large Piwinski angle. The LER spin rotator sections provide longitudinal polarization for the electron beam at IP. The lattice is flexible for tuning the design parameters and compatible with reusing the PEP-II magnets, RF cavities and other components. Design criteria and details on the lattice implementation are presented.
INFN/LNF, Frascati (Roma)
An innovatory interaction region has been recently conceived and realized on the Frascati DAΦNE lepton collider. The concept of tight focusing and small crossing angle adopted until now to achieve high luminosity in multibunch collisions has evolved 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 term 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 integral 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.
University of Pisa and INFN, Pisa
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
SuperB is an international project for an asymmetric 2 rings collider at the B mesons cm energy to be built in the Rome area in Italy. The two rings will have very small beam sizes at the Interaction Point and very small emittances, similar to the Linear Collider Damping Rings ones. In particular, the ultra low vertical emittances, 7 pm in the LER and 4 pm in the HER, need a careful study of the misalignment errors effects on the machine performances. Studies on the closed orbit, vertical dispersion and coupling corrections have been carried out in order to specify the maximum allowed errors and to provide a procedure for emittance tuning. A new tool which combines MADX and Matlab routines has been developed, allowing for both corrections and tuning. Results of these studies are presented.
SLAC, Menlo Park, California
CERN, Geneva
University of Pisa and INFN, Pisa
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
A final focus magnet design that uses super-ferric magnets is introduced for the Super-B interaction region. The baseline design has air-core super-conducting quadrupoles. This idea instead uses super-conducting wire in an iron yoke. The iron is in the shape of a Panofsky quadrupole and this allows for two quadrupoles to be side-by-side with no intervening iron as long as the gradients of the two quads are equal. This feature allows us to move in as close as possible to the collision point and minimize the beta functions in the interaction region. The super-ferric design has advantages as well as drawbacks and we will discuss these in the paper.
SLAC, Menlo Park, California
Cockcroft Institute, Warrington, Cheshire
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
The availability of longitudinally polarized electrons is an important aspect of the design of the proposed SuperB project at LNF Frascati. Spin rotators are an integral part of the design of the Interaction Region (IR). We have chosen a solenoid-dipole design; at the 4.18 GeV nominal energy this is more compact that a design purely based on dipole magnets. Integration with the local chromaticity correction of the ultra-low beta* IR has been achieved. The spin rotators are symmetric about the Interaction Point, this design saves a significant amount of length as the dipoles become a part of the overall 360 deg. bend. The layout leaves limited opportunity to setup the optics for minimum depolarization; this is acceptable since beam life time in SuperB at high luminosity is only about 5 min and up-to 90% polarized electrons will be injected continuously. In this way an average beam polarization of about 70% is maintained. Simulations and analytic estimates with the DESY code SLICKTRACK and other codes indicate such operation is feasible from a spin-dynamics point of view. The paper will discuss the overall spin-rotator design as well as the spin dynamics in the ring.
LAL, Orsay
INFN/LNF, Frascati (Roma)
IN2P3 IPNL, Villeurbanne
Providing a high quality and sufficient high current positron beam for the ultra high luminosity B-factory SuperB is a major goal. In this paper a proposition for positrons production and capture scheme based on low energy electrons up to1 GeV is presented. For this technique, several types of flux concentrator used to capture the positrons are being studied. The following accelerating section bringing the positrons up to 280 MeV and the total yield for L-band and S-band type accelerators are given. Also the result of the benchmark between ASTRA and a LAL code based on Geant4 toolkit simulation is discussed.
INFN/LNF, Frascati (Roma)
LPSC, Grenoble
SLAC, Menlo Park, California
CERN, Geneva
IN2P3-LAPP, Annecy-le-Vieux
LAL, Orsay
INFN-Pisa, Pisa
CEA, Gif-sur-Yvette
IN2P3 IPNL, Villeurbanne
BINP SB RAS, Novosibirsk
University of Pisa and INFN, Pisa
The SuperB project is an international effort aiming at building in Italy a very high luminosity e+e- (1036 cm-2 sec-1) asymmetric collider at the B mesons cm energy. The accelerator design has been extensively studied and changed during the past year. The present design, - based on the new collision scheme, with large Piwinski angle and the use of 'crab' sextupoles, which has been successfully tested at the DAPHNE Phi-Factory at LNF Frascati, - provides larger flexibility, better dynamic aperture and in the Low Energy Ring spin manipulation sections, needed for having longitudinal polarization of the electron beam at the Interaction Point. The Interaction Region has been further optimized in terms of apertures and reduced backgrounds in the detector. The injector complex design has been also updated. A summary of the design status, including details on lattice and spin manipulation will be presented in this paper.
INFN/LNF, Frascati (Roma)
CERN, Geneva
BINP SB RAS, Novosibirsk
Recently the peak luminosity achieved on the DAΦNE collider has been improved by almost a factor 3 by implementing a novel collision scheme based on large Piwinski angle and Crab-Waist. This encouraging result opened new perspectives for physics 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.
INFN/LNF, Frascati (Roma)
BINP SB RAS, Novosibirsk
In DAΦNE, the Frascati e+/e- collider, the crab waist collision scheme has been successfully implemented in 2008 and 2009. During the collision operations for Siddharta experiment, an unusual synchrotron damping effect has been observed. Indeed, with the longitudinal feedback switched off, the positron beam becomes unstable with beam currents in the order of 200-300 mA. The longitudinal instability is damped by bringing the positron beam in collision with a high current electron beam (~2A). Besides, we have observed a shift of ≈600Hz in the residual synchrotron sidebands. Precise measurements have been performed by using a commercial spectrum analyzer and by using the diagnostics capabilities of the DAΦNE longitudinal bunch-by-bunch feedback. This damping effect has been observed in DAΦNE for the first time during collisions with the crab waist scheme. Our explanation is that beam collisions with a large crossing angle produce a longitudinal tune shift and a longitudinal tune spread, providing Landau damping of synchrotron oscillations.
INFN/LNF, Frascati (Roma)
CEA, Gif-sur-Yvette
LAL, Orsay
SLAC, Menlo Park, California
The ultra high luminosity B-factory (SuperB) project of INFN requires a high performance and reliable injection system, providing electrons at 4 GeV and positrons at 7 GeV, to fulfill the very tight requirements of the collider. Due to the short beam lifetime, continuous injection of electrons and positrons in both HER and LER rings is necessary to keep the average luminosity at a high level. Polarized electrons are required for experiments and must be delivered by the injection system, due to the beam lifetime shorter than the polarization build-up: they will be produced by means of a SLAC-SLC polarized gun. One or two 1 GeV damping rings are used to reduce e+ and e- emittances. Two schemes for positron production are under study, one with electron-positron conversion at low energy (<1 Gev), the second at 6 GeV with a recirculation line to bring the positrons back to the damping ring. Acceleration through the Linac is provided by a S-band RF system made of traveling wave, room temperature accelerating structures. An option to use the C-band technology is also presented.
CERN, Geneva
INFN/LNF, Frascati (Roma)
The wigglers of the DAΦNE main rings have been one of the main sources of the non-linearities in the collider. A method to minimize the odd integrated multipoles around the beam trajectory (the even ones tend to vanish due to the periodicity of the device) is described. It consists in displacing the magnetic axis of each pole towards the position of the beam in such a way that the integrated odd multipoles are minimized in each half period of the wiggler. After a study, including multipolar and tracking analysis, has performed to determine the best position of the axes, the wigglers in the DAΦNE main rings have been modified accordingly. To validate this approach magnetic measurements and tests with beam by means of closed orbit bumps have been performed.