INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
CERN, Geneva
BINP SB RAS, Novosibirsk
KEK, Ibaraki
University of Pisa and INFN, Pisa
The SuperB project aims at the construction of an asymmetric (4x7 GeV), very high luminosity, B-Factory on the Roma II (Italy) University campus. The luminosity goal of 1036 cm-2 s-1 can be reached with a new collision scheme with large Piwinski angle and the use of “crab” sextupoles. A crab-waist IR has been successfully tested at the DAPHNE Phi-Factory at LNF-Frascati (Italy) in 2008. The crab waist together with very low beta* will allow for operation with relatively low beam currents and reasonable bunch length, comparable to those of PEP-II and KEKB. In the High Energy Ring, two spin rotators permit bringing longitudinally polarized beams into collision at the IP. The lattice has been designed with a very low intrinsic emittance and is quite compact, less than 2 km long. The tight focusing requires a sophisticated Interaction Region with quadrupoles very close to the IP. A Conceptual Design Report was published in March 2007, and beam dynamics and collective effects R&D studies are in progress in order to publish a Technical Design Report by the end of 2010. A status of the design and simulations is presented in this paper.
INFN/LNF, Frascati (Roma)
LAL, Orsay
CERN, Geneva
roma3, Rome
Rome University La Sapienza, Roma
BINP SB RAS, Novosibirsk
KEK, Ibaraki
BINP, Novosibirsk
SLAC, Menlo Park, California
INFN-Roma, Roma
In 2007 DAΦNE was upgraded to operate in a regime of large Piwinski angle, with a novel IR optics, reduced vertical beta at the interaction point, and additional sextupoles providing for crab waist collisions. The specific luminosity was boosted by more than a factor of four, and the peak luminosity was more than doubled with respect to the maximum value obtained with the original collider configuration. The DAΦNE commissioning as well as the first experience with large Piwinski angle and crab waist collisions scheme will be reported.
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
Funding: Work supported by the U.S. Department of Energy under contract number DE-AC03-76SF00515.
The use of normal conducting cavities and an ion-clearing gap will cause a significant RF accelerating voltage gap transient and longitudinal phase shift of the individual bunches along the bunch train in both rings of the SuperB accelerator. Small relative centroid position shifts between bunches of the colliding beams will have a large adverse impact on the luminosity due to the small beta y* at the interaction point (IP). We investigate the possibility of minimizing the relative longitudinal position shift between bunches by reducing the gap transient in each ring and matching the longitudinal bunch positions of the two rings at the IP using feedback/feedforward techniques in the LLRF. The analysis is conducted assuming maximum use of the klystron power installed in the system.
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
Funding: Work supported by the Department of Energy under contract number DE-AC03-76SF00515.
We present a possible design for a fast luminosity feedback for the Super-B Interaction Point (IP). The design is an extension of the fast luminosity feedback installed on the PEP-II accelerator. During the last two runs of PEP-II and BaBar (2007-2008), we had an improved luminosity feedback system that was able to maintain peak luminosity with faster correction speed than the previous system. The new system utilized fast dither coils on the High-Energy Beam (HEB) to independently dither the x position, the y position and the y angle at the IP, at roughly 100 Hz. The luminosity signal was then read out with three independent lock-in amplifiers. An overall correction was computed based on the lock-in signal strengths and beam corrections for position in x and y and in the y angle at the IP were simultaneously applied to the HEB. With the 100 times increase in luminosity for the SuperB design, we propose using a similar fast luminosity feedback that can operate at frequencies between DC and 1 kHz, high enough to be able to follow and nullify any vibrational beam motion from the final focusing magnets.
INFN/LNF, Frascati (Roma)
USTC/NSRL, Hefei, Anhui
VIGO System S.A., Ozarow Maz.
Real time diagnostics is a fundamental tool for accelerator physics, particularly important to improve performances of existing synchrotron radiation sources, colliders and a key issue for 4th generation sources and FELs. We report the first measurements in the time and frequency domain performed at Hefei Light Source (HLS), the SR facility of the National Synchrotron Radiation Laboratory (NSRL), of the longitudinal bunch lengths. A fast uncooled HgCdTe photodiode optimized in the mid-IR range has been used to record at the IR port the length of the e- bunches. IR devices are compact and low cost detectors suitable for a bunch-by-bunch longitudinal diagnostics. The data are useful to investigate longitudinal oscillations and characterize the bunch length. The IR signal has been used to measure the synchrotron oscillation frequency, its harmonics in the multi-bunch mode and the bunch lengths in multi-bunch mode at different beam currents. For the first time, simultaneously, data have been collected at visible wavelengths using a fast photodiode at the diagnostics beamline of HLS. A comparison between IR data and diagnostics realized in the visible will be presented and discussed.
INFN/LNF, Frascati (Roma)
In the more than decennial history of DAΦNE, the Frascati e+/e- collider, the positron beam has always shown more difficulty to store high current than the e- beam. Given that the two rings are identical, many types of measurement have been tried to figure out the problem and to solve it, but eventually only one technique has presented a crucial utility: the modal grow rate measurement. In principle this method could be implemented using a commercial spectrum analyzer with the right software procedure inside. Nevertheless it is much easier and faster to record data by the bunch by bunch feedback diagnostics and to use for analyzing the offline feedback programs. A large campaign of data taking has been done in DAΦNE main rings during last fall. A comparison with grow rate records from previous years has point out clearly the difference with 2008 DAΦNE performance showing the way to solve the beam current limit. In particular, measurements have been done versus different machine conditions. Very fast horizontal instability present only in the e+ ring has been characterized showing linear behavior versus beam current. These data have been used to figure out the current limit problem.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
At the LNF (Laboratori Nazionali di Frascati) of the INFN a novel diagnostics experiment has been set-up to monitor the real time bunch behavior in the positron ring of the DAΦNE collider. The experiment has been installed on a bending magnet exit port of the e+ ring. The front-end consists of a UHV chamber where a gold-coated plane mirror deflects the radiation through a ZnSe window. After the window, a compact optical layout in air focuses the radiation on an IR detector. Compact mid-IR fast uncooled HgCdTe photodiodes are used to measure the bunch by bunch emission. A preliminary alignment of the mirrors and a first characterization of the radiation emitted have been performed. Longitudinal measurements of the bunch behavior, both in time and in frequency domain, obtained with fast IR detectors are presented. This novel diagnostics now available is ready to allow monitoring in real time of the bunch-by-bunch positron emission. It has been designed to improve the DAΦNE diagnostics with the main aim to identify and characterize positron bunch instabilities in the longitudinal plane. Developments for extending detection capability in the transverse planes are in progress.
INFN/LNF, Frascati (Roma)
The SuperB project consists of an asymmetric (4x7 GeV), very high luminosity, B-Factory to be built at Roma-II University campus in Italy, with the ambitious luminosity goal of 1036 cm-2 s-1. To achieve the very challenging performances, robust and powerful bunch-by-bunch feedback systems are necessary to cope with fast coupled bunch instabilities in rings with high beam currents and very low emittances. The SuperB bunch by bunch feedback should consider the rich legacy of previous systems, the longitudinal (DSP-based) feedback built in 1993-97 and the recent “iGp” feedback system designed in 2002-06. Both were designed by large collaborations between Research Institute (SLAC, DAΦNE@LNF/INFN, ALS@LBNL, KEK). The core of the new system will be the digital processing module, based on powerful FPGA components, to be used in longitudinal and transverse planes. Off-line analysis programs, as well real-time diagnostic tools, will be included. The feedback impact on very low emittance beams have to be carefully considered. A MATLAB simulator based on a beam/feedback model is also foreseen for performance checks and fast downloads of firmware/gateware code and parameters.
INFN/LNF, Frascati (Roma)
In this paper the horizontal feedback upgrade for the positron DAΦNE ring is presented. After having completed the analysis of the e+ current limit behavior, a feedback upgrade has been turned out necessary. For the success of the crab waist experiment in the 2008 year, a fast solution to implement the upgrade has been necessary. It has been considered if a simple power increase would be the best solution. The lack of power combiners and of space for other two power amplifiers has brought to a different approach, doubling the entire feedback system. The advantages of this implementation respect to a more traditional power amplifier doubling are evident: two feedback kicks every revolution turns, better use of the power amplifiers, greater reliability, and less coherent noise in the system. Measurements of the two feedbacks have shown a perfect equivalence of the new and the old system: in fact the resulting damping rate is exactly the double of each system taken individually. A description of the implementation is presented together with the performance of the system.
INFN/LNF, Frascati (Roma)
KEK, Ibaraki
Funding: Work supported in part by the “Ministero degli Affari Esteri, Direzione Generale per la Promozione e la Cooperazione Culturale”
A strong horizontal instability has been observed in the DAΦNE positron ring since 2003. Experimental observations suggest an electron cloud induced coupled bunch instability as a possible explanation. In this communication we present a simulation study of the electron cloud coupled bunch instability for the DAΦNE positron ring, performed with the code PEI-M, and compare the numerical results with experimental observations.
INFN/LNF, Frascati (Roma)
U. Sannio, Benevento
INFN-Salerno, Baronissi, Salerno
The electron cloud driven effects can limit the ability of recently build or planned accelerators to reach their design parameters. The secondary emission yield reduction (called "scrubbing") due to the fact that the electrons of the cloud hit the vacuum chamber wall, modifying its surface properties, may minimize any disturbing effects of the cloud to the beam. The dependence of "scrubbing" efficiency on beam and chamber parameters can be deduced from e-cloud simulation codes modeling the involved physics in full detail. In this communication we present a generalization of the map formalism, introduced in*,**, for the analysis of electron flux at the chamber wall with particular reference to the exploration of LHC conditioning scenarios. Simulations based on this formalism are orders of magnitude faster compared to those based on standard particle tracking codes.
*U.Iriso and S.Peggs, ”Maps for Electron Clouds”, Phys. Rev. ST-AB 8, 024403, 2005.
**T.Demma et al., ”Maps for Electron Clouds: Application To LHC”, Phys. Rev. ST-AB 10, 114401 (2007).
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
CEA, Gif-sur-Yvette
INFN-Roma II, Roma
ENEA C.R. Frascati, Frascati (Roma)
SOLEIL, Gif-sur-Yvette
INFN-Roma, Roma
University of Tehran, Tehran
UCLA, Los Angeles, California
The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in SASE, Seeding and Single Spike configurations. The SPARC photoinjector is also the test facility for the recently approved VUV FEL project named SPARX. The second stage of the commissioning, that is currently underway, foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching , the demonstration of the “velocity bunching” technique in the linac and the characterisation of the spontaneous and stimulated radiation in the SPARC undulators. In this paper we report the experimental results obtained so far. The possible future energy upgrade of the SPARC facility to produce UV radiation and its possible applications will also be discussed.