SLAC, Menlo Park, California
SLAC, Menlo Park, California
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
Royal Holloway, University of London, Surrey
LAL, Orsay
BNL, Upton, Long Island, New York
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
UMAN, Manchester
CERN, Geneva
Fermilab, Batavia, Illinois
DESY, Hamburg
OXFORDphysics, Oxford, Oxon
Cockcroft Institute, Warrington, Cheshire
ANL, Argonne, Illinois
JAI, Oxford
CEA, Gif-sur-Yvette
STFC/RAL, Chilton, Didcot, Oxon
KEK, Ibaraki
UU/ISV, Uppsala
LLNL, Livermore, California
Kyoto ICR, Uji, Kyoto
DESY Zeuthen, Zeuthen
STFC/DL, Daresbury, Warrington, Cheshire
UBC, Vancouver, B. C.
University of Tokyo, Tokyo
BINP SB RAS, Novosibirsk
University of Oregon, Eugene, Oregon
Colorado University at Boulder, Boulder, Colorado
Birmingham University, Birmingham
Tohoku University, Sendai
SLAC, Menlo Park, California
ANL, Argonne, Illinois
Undulator-based positron source is adopted as the International Linear Collider baseline design. Complete optics to transport the positron beam having large angular divergence and large energy spread from a thin Ti target to the entrance of the 5 GeV damping ring injection line is developed. Start-to-end multi-particle tracking through the beamline is performed including the optical matching device, capture accelerator system, transport system, superconducting booster linac, spin rotators, and energy compressor. Positron capture efficiency of different schemes (immersed vs shielded target, and flux concentrator vs quarter wave transformation for the optics matching system) is compared. For the scheme of a shielded target and quarter wave transformation, the simulation shows that 15.1% of the positrons from the target are captured within the damping ring 6-D acceptance at the entrance of the damping ring injection line.
BNL, Upton, Long Island, New York
SLAC, Menlo Park, California
A wide variety of superconducting magnets are needed in the ILC Beam Delivery System (BDS) to maximize luminosity and minimize experimental backgrounds. Compact final focus quadrupoles and multifunction correction coils are used with 14 mr total crossing angle to focus incoming beams to few nanometer spot sizes while focusing outgoing disrupted beams into a separate extraction beam line. Large aperture anti-solenoids correct deleterious nonlinear effects that arise due to the overlap of focusing fields with the main detector solenoid. Far from the interaction point (IP) sets of strong small aperture octupoles help minimize backgrounds at the IP due to beam halo particles while weak large aperture dipoles integrated with the experimental detector reduce backgrounds due to beamstrahlung pairs generated at the IP. The physics requirements and magnetic design solutions for these magnets are reviewed in this paper.
SLAC, Menlo Park, California
Orbit bumps in sextupoles are routinely used for tuning the luminosity in the PEP-II B-Factory. Anti-symmetric bumps in a sextupole pair generate dispersion, while symmetric bumps induce a tune shift and beta beat. By coming two of these symmetric bumps with opposite signs where the second pair is 90 degree away, the tune shift cancels and the beta beat doubles. In the low energy ring (LER) we have four sextupole pairs per arc, where pair 1 and 3 are at the same betatron phase and pair 2 and 4are 90 degree away. By making two symmetric bumps with opposite sign in pair 1 and 3 the tune shift and the beta beat outside this region cancel, BUT the LER lifetime improved by a factor of three, losses by a factor of five, and the beam-beam background in the drift chamber of the BaBar detector by 20%. Simulations showed that the phase change at the second sextupole pair introduced by the beta beat can completely cancel the third order chromaticity.
SLAC, Menlo Park, California
The low energy ring (LER) in PEP-II has a design emittance of 0.5 nm-rad in the vertical, compared to nearly 0.1 nm-rad for the HER ring. This was thought to come from the "vertical step" of about 1 m in the interaction straight, where the LER beam after horizontal separation gets bend vertical so it sits on top of the HER in the rest of the ring. Since the program MAD does not easily reveal the location of the major emittance contribution, a program was written to calculate the coupled "curly H" parameter of mode 2 (mainly vertical) along z. Weighting it with the magnet bending revealed that the weak long bends inside the "vertical step" did less than 20% of the emittance growth. More than 80% comes from the ends of the adjacent arcs with strong bends. This is caused by the coupling cancellation of the solenoid starting already there with the skew quadrupoles SK5 and 6. By introducing additional skews in the straight instead of SK5 and 6 the emittance could be reduced by a factor of ten in simulations, but with very strong skews. Reasonable strong magnets might generate a workable compromise, since a factor of two in emittance promises 50% more luminosity in beam-beam simulations.