Wiggler insertion of the PEP-II B-Factory LER

Heim, J.R.; Bertolini, L.; Dressler, John L.; Fackler, O.; Hobson, B. F.; Kendall, Michael R.; O’Connor, Thomas G.; Stoeffl, W.; Swan, T.

doi:10.1109/pac.1995.504708

Cited by 6 publications

(4 citation statements)

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“…In the wiggler chicane, IR-6, we utilize an extended copper photon dump [4]. This chamber must maintain a good vacuum while absorbing up to 250 kW of synchrotron radiation power along both sides of its 25-m length.…”

Section: Vacuum Systemmentioning

confidence: 99%

The PEP-II Project: Low-Energy Ring Design and Project Status

Zisman¹

2006

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We describe the present status of the PEP-II project. The project comprises four major systems: Injector, High-Energy Ring (HER), Low-Energy Ring (LER), and Interaction Region (IR). We focus in detail on the design of the LER, as its parameters and requirements are most closely related to those required for the Beijing Tau-Charm Factory rings. The PEP-II LER is a high-current, 3.1-GeV positron ring mounted above the 9-GeV HER. The LER uses a wiggler located in one of its six straight sections to provide emittance control and additional damping. We describe the rather complicated IR, which must transport the LER beam into the plane of the HER, focus it to a common beam size, and separate the beams after the head-on collisions. Both permanent magnet and conventional electromagnets are used in this area. The LER lattice has now adopted a simplified non-interleaved sextupole correction scheme that has reduced the required number of sextupoles substantially. We describe the LER vacuum system, one of the most challenging subsystems in PEP-II. It employs several technologies. In the arcs, aluminum extrusions and titanium sublimation pumps are employed; the straight sections use stainless steel chambers with lumped ion pumps. In the wiggler area, an extended copper photon dump with nonevaporable getter (NEG) pumps is employed to handle the very large synchrotron radiation power. The design of the room-temperature RF system, the bunch-by-bunch longitudinal and transverse feedback systems, and some of the special diagnostics will be described briefly. The PEP-II project remains on schedule to begin commissioning of the HER in April 1997, followed by the LER a year later.

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Section: Vacuum Systemmentioning

confidence: 99%

The PEP-II Project: Low-Energy Ring Design and Project Status

Zisman¹

2006

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“…First we used a damping time of 5400 turns as it is in [l]; second we took a damping time of 7200 turns, as proposed in [8]. In Figure 2, we show tlie dependence of the lifetime versus beam-beam parameters for our two cases.…”

Section: Damping Timementioning

confidence: 99%

Lifetime and tail simulations for beam-beam effects in PEP-II B Factory

Shatilov

Zholents

Proceedings Particle Accelerator Conference

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A fast tracking technique for doing beam tail simulations has been applied to a study of beam-beam effects in the SLAC/LBL/LLNL PEP-I1 B Factory. In particular, the dependence of beam lifetime and particle density distribution due to vacuum pressure, damping times, machine nonlinearity and parasitic crossings has been analyzed. Effects of accidental orbit separation and dispersion function at the interaction point (IP) have also been considered. I. BEAM PARAMETERS AND MODELBeam and machine parameters for PEP-I1 B factory are described elsewhere [l]. For the sake of completeness, we reproduce in the Table I all parameters we need for a discussion of beam-beam effects. Our notation for most of the parameters has a standard and obvious meaning. Only a few definitions need explanation. In the PEP-I1 B factory, electron and positron bunches collide head-on at the IP. After the IP, beam orbits are inagiletically separated in the horizontal plane. However, before entering its own vacuum pipe, each electron bunch and each positron buiich experiences four more interactions with other bunches of the opposite beam. We refer to these interactions as parasitic crossings (PC's). A parameter dsep defines orbit separation at the first PC. Orbit separation at the remaining PCs is much larger and, consequently, the effect of beam-beam interactions at these P C is negligible. We will ignore them in our model and will consider only the first parasitic crossing on either side of the IP. Parameters Av, and Av, define horizontal and vertical betatron phase advance, in units of the betatron tune, from the main IP to the first PC.A goal of our study was understanding the mechanisms leading to a beam lifetime limitation in electron-positron colliders. According to experimental observations [2], these mechanisms are fairly insensitive to particle density distribution in the beam core. Thus, a weal-strong model of beam-beam effects seems adequate to our task.All our simulations were carried out with the beam-beam program LIFETRAC [3]. This program allows the following physics to be included in the simulation:1. Beam-beam kick. 2. One turn, six-dimensional linear map. 3. Chromaticity up to the third order:

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“…The large currents in each bunch require that the transverse emittance of the beams be moderately large to maintain a reasonably small beam-beam tune shift parameter. The magnitude of the horizontal emittance is controlled, in the LER by wiggler magnets [3] and in the HER by tailoring the dispersion function in four of the six arcs.…”

Section: Hermentioning

confidence: 99%

Lattice design for the High Energy Ring of the SLAC B-Factory (PEP-II)

Donald

Cai

Irwin

et al.

Proceedings Particle Accelerator Conference

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The design of the lattice for the High Energy Ring (HER) of the SLAC &Factory has several special features, notably provision for octupole compensation of amplitude dependent tune shift effects and a beta-beat scheme for semi-local chromaticity correction. In the arcs adjacent to the interaction point (IP) the beta functions are enhanced to allow the use of non-interlaced sextupoles to compensate the chromaticity of the interaction region. A closed bump of beta "mismatch" is generated by two vertically focusing quadrupoles spaced 2 betatron wavelengths apart. The beta-beat has two advantages: it enhances the ratio between the horizontal and vertical beta functions at the &tupoles and, because of the locally higher beta function, allows weaker sextupoles to be used. The standard design uses a 60 degree/cell lattice but a 90 degree/cell lattice may also be used if lower emittances and momentum compaction factor are desired.

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Wiggler insertion of the PEP-II B-Factory LER

Cited by 6 publications

References 1 publication

The PEP-II Project: Low-Energy Ring Design and Project Status

The PEP-II Project: Low-Energy Ring Design and Project Status

Lifetime and tail simulations for beam-beam effects in PEP-II B Factory

Lattice design for the High Energy Ring of the SLAC B-Factory (PEP-II)

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