SLAC, Menlo Park, California
Funding: Work supported by US DOE contract DE-AC03-76SF00515.
Second-generation B-Factory proposals are being considered both by KEK in Japan (Super KEKB) and by an INFN Frascati/SLAC/CalTech collaboration in Italy (Super-B). Novel collision schemes like crab waist with crab-sextupoles and also crab cavities are being proposed to mitigate the beam-beam effects of a large crossing angle. The talk will present concepts from both proposals in the context of the experience with the present PEP-II and KEKB B-Factories, which have been successful far beyond the initial performance goals.
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)
SLAC, Menlo Park, California
The SuperB collider project aims at the construction of an asymmetric high luminosity B-Factory in the Tor Vergata University campus in Rome (Italy). The engineering aspects of the SuperB design and construction with the aim to reuse at maximum the PEP II components will be presented. Sinergies with the Italian FEL project SPARX, which will start civil construction this year, will be discussed. The two projects can share the Linac tunnel and other facilities. A study of ground motion will also be presented.
SLAC, Menlo Park, California
CERN, Geneva
INFN/LNF, Frascati (Roma)
University of Pisa and INFN, Pisa
Funding: Work supported by the Department of Energy under contract number DE-AC03-76SF00515.
We present an improved design for a Super-B interaction region. The new design minimizes local bending of the two colliding beams by separating all beam magnetic elements near the Interaction Point (IP). The total crossing angle at the IP is increased from 50 mrad to 60 mrad. The first magnetic element is a six slice Permanent Magnet (PM) quadrupole with an elliptical aperture allowing us to increase the vertical space for the beam. This magnet starts 36 cm from the Interaction Point (IP). This magnet is only seen by the Low-Energy Beam (LEB), the High-Energy Beam (HEB) has a drift space at this location. This allows the preliminary focusing of the LEB which has a smaller beta y* at the IP than the HEB. The rest of the final focusing for both beams is achieved by two super-conducting side-by-side quadrupoles (QD0 and QF1). These sets of magnets are enclosed in a warm bore cryostat located behind the PM quadrupole for the LEB. We describe this new design for the interaction region.
SLAC, Menlo Park, California
Funding: Work supported by the Department of Energy under contract number DE-AC03-76SF00515.
The PEP-II B-Factory was designed and optimized to run at the Upsilon 4S resonance (10.580 GeV with a 9 GeV e- beam and a 3.1 GeV e+ beam). The interaction region (IR) used permanent magnet dipoles to bring the beams into a head-on collision. The first focusing element for both beams was also a permanent magnet. The IR geometry, masking, beam orbits and beam pipe apertures were designed for 4S running. Even though PEP-II was optimized for the 4S, we successfully changed the center-of-mass energy (Ecm) down to the Upsilon 2S resonance and completed an Ecm scan from the 4S resonance up to 11.2 GeV. The luminosity throughout these changes remained near 1x1034 cm-2s-1 . The Ecm was changed by moving the energy of the high-energy beam (HEB). The beam energy differed by more than 20% which produced significantly different running conditions for the RF system. The energy loss per turn changed 2.5 times over this range. We describe how the beam energy was changed and discuss some of the consequences for the beam orbit in the interaction region. We also describe some of the RF issues that arose and how we solved them as the high-current HEB energy changed.
SLAC, Menlo Park, California
Funding: This work is supported by the Department of Energy contract DE-AC02-76SF00515.
FACET is a proposed facility at SLAC National Accelerator Laboratory for beam driven plasma wakefield acceleration research. It is proposed to be built in the SLAC linac sector 20, where it will be separated from the LCLS located downstream and will gain the maximum beam energy from the upstream two kilometers of linac. FACET will also include an upgrade to linac sector 10, where a new e+ compressor chicane will be installed. The sector 20 will require a new optics consisting of two chicanes for e+ and e- bunch length compression, a final focus system and an extraction line. The two chicanes will allow the transport of e- and e+ bunches together, their simultaneous compression and proper positioning of e+ bunch behind e- at the plasma Interaction Point (IP). For a minimal cost, the new optics will mostly use the existing SLAC magnets. The desired beam parameters at the IP are: up to 23 GeV beam energy, 2·1010 charge per bunch, 10 micron round beam spot without dispersion and 25 micron bunch length. Details of the FACET optics design and results of particle tracking simulations are presented.
SLAC, Menlo Park, California
Stanford University, Stanford, California
UCLA, Los Angeles, California
Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515.
SSRL and SLAC groups are developing a long-range plan to transfer its evolving scientific programs from the SPEAR3 light source to a much higher performing photon source that would be housed in the 2.2-km PEP-II tunnel. While various concepts for the PEP-X light source are under consideration, including ultimate storage ring and ERL configurations, the present baseline design is a very low-emittance storage ring. A hybrid lattice has DBA or QBA cells in two of the six arcs that provide a total ~30 straight sections for ID beam lines extending into two new experimental halls. The remaining arcs contain TME cells. Using ~100 m of damping wigglers the horizontal emittance at 4.5 GeV would be ~0.1 nm-rad with >1 A stored beam. PEP-X will produce photon beams having brightnesses near 1022 at 10 keV. Studies indicate that a ~100-m undulator could have FEL gain and brightness enhancement at soft x-ray wavelengths with the stored beam. Crab cavities or other beam manipulation systems could be used to reduce bunch length or otherwise enhance photon emission properties. The present status of the PEP-X lattice and beam line designs are presented and other implementation options are discussed.
SLAC, Menlo Park, California
Funding: work supported by the Department of Energy under contract number DE-AC03-76SF00515
We present the history and analysis of different wake field effects throughout the operational life of the PEP-II SLAC B-factory. Although the impedance of the high and low energy rings is small, the high current intense beams generated a lot of power. These wake field effects are: heating and damage of vacuum beam chamber elements like RF seals, vacuum valves , shielded bellows, BPM buttons and ceramic tiles; vacuum spikes, vacuum instabilities and high detector background; beam longitudinal and transverse instabilities. We also discuss the methods used to eliminate these effects. Results of this analysis and the PEP-II experience may be very useful in the design of new storage rings and light sources.