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To achieve maximum luminosity at the SLC, both the electron and positron beams must reach their minimum transverse size within 1 mm of the longitudinal location where the two bunches collide. This paper describes an automated procedure for positioning the focal point of each beam at this collision point. The technique is based on measurements of the beam size utilizing either secondary emission or bremsstrahlung signals from carbon fibers a few microns in diameter. We have achieved simultaneous and reproducible measurements of the angular spread (~ 200 [mu] rad) and of the optimum beam spot size ~ [omega]m), which when combined yield measurements of the beam emittance consistent with those obtained using conventional profile monitor techniques.
We present studies of accelerator-induced backgrounds in the BaBar detector at the SLAC B-Factory, carried out using LPTURTLE, a modified version of the DECAY TURTLE simulation package. Lost-particle backgrounds in PEP-II are dominated by a combination of beam-gas bremstrahlung, beam-gas Coulomb scattering, radiative- Bhabha events and beam-beam blow-up. The radiation damage and detector occupancy caused by the associated electromagnetic shower debris can limit the usable luminosity. In order to understand and mitigate such backgrounds, we have performed a full programme of beamgas and luminosity-background simulations, that include the effects of the detector solenoidal field, detailed modelling of limiting apertures in both collider rings, and optimization of the betatron collimation scheme in the presence of large transverse tails.
Comment: Poster presented to European Particle Accelerator Conference (EPAC'06), Edinburgh, Scotland, 26-30 June 2006
To achieve maximum integrated luminosity at the SLAC Linear Collider, a method of noninvasive beam tuning is required. Traditional luminosity monitors based on Bhabha scattering are inadequate because of low instantaneous counting rates. Coherent deflections of one beam by the electromagnetic field of the other are sensitive not only to the relative steering of the two bunches but also to their spot sizes. A brief description of beam-beam deflection theory forms the basis for a discussion of this phenomenon as a tool for single-beam tuning and for luminosity optimization at the interaction point of the SLC.
Fine conductive fibers have been used to measure transverse beam dimensions of a few microns at the Stanford Linear Collider (SLC). The beam profile is obtained by scanning a fiber across the beam in steps as small as 1 [mu]m, and recording the secondary emission signal at each step, using a charge sensitive amplifier. We first outline the mechanical construction and the analogue electronics of the wire scanner. We then describe its performance in test beams and in actual operation. The article closes with a brief discussion of performance limitations of such a beam profile monitor.
Comment: 4 pages, 4 figures, presented at the 7th European Particle Accelerator Conference (EPAC 2000), Vienna, Austria, June 26-30, 2000
The physics accessible at the high-luminosity phase of the LHC extends well beyond that of the earlier LHC program. This white paper, submitted as input to the Snowmass Community Planning Study 2013, contains preliminary studies of selected topics, spanning from Higgs boson studies to new particle searches and rare top quark decays. They illustrate the substantially enhanced physics reach with an increased integrated luminosity of 3000 fb-1, and motivate the planned upgrades of the LHC machine and ATLAS detector.
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