4,960 research outputs found

    An automated focal point positioning and emittance measurement procedure for the interaction point of the SLC

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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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28674/1/0000491.pd

    Microstructures Manufactured in Diamond by Use of Laser Micromachining.

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    Different microstructures were created on the surface of a polycrystalline diamond plate (obtained by microwave plasma-enhanced chemical vapor deposition-MW PECVD process) by use of a nanosecond pulsed DPSS (diode pumped solid state) laser with a 355 nm wavelength and a galvanometer scanning system. Different average powers (5 to 11 W), scanning speeds (50 to 400 mm/s) and scan line spacings ("hatch spacing") (5 to 20 µm) were applied. The microstructures were then examined using scanning electron microscopy, confocal microscopy and Raman spectroscopy techniques. Microstructures exhibiting excellent geometry were obtained. The precise geometries of the microstructures, exhibiting good perpendicularity, deep channels and smooth surfaces show that the laser microprocessing can be applied in manufacturing diamond microfluidic devices. Raman spectra show small differences depending on the process parameters used. In some cases, the diamond band (at 1332 cm-1) after laser modification of material is only slightly wider and shifted, but with no additional peaks, indicating that the diamond is almost not changed after laser interaction. Some parameters did show that the modification of material had occurred and additional peaks in Raman spectra (typical for low-quality chemical vapor deposition CVD diamond) appeared, indicating the growing disorder of material or manufacturing of the new carbon phase

    Machine-Related Backgrounds in the SiD Detector at ILC

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    With a multi-stage collimation system and magnetic iron spoilers in the tunnel, the background particle fluxes on the ILC detector can be substantially reduced. At the same time, beam-halo interactions with collimators and protective masks in the beam delivery system create fluxes of muons and other secondary particles which can still exceed the tolerable levels for some of the ILC sub-detectors. Results of modeling of such backgrounds in comparison to those from the e+ e- interactions are presented in this paper for the SiD detector.Comment: 29 pages, 34 figures, 7 table

    Beam-beam deflection as a beam tuning tool at the SLAC linear collider

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    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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28771/1/0000603.pd

    Comparison of the TESLA, NLC and CLIC Beam Collimation Systems Performance

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    This note describes studies performed in the framework of the Collimation task Force organized to support work of the International Linear Collider Technical Review Committee aiming in comparison of performance of the post-linac beam collimation systems in TESLA, JLC/NLC and CLIC linear collider designs. Collimation of the beam halo and synchrotron radiation collimation have been compared for all projects using the same computer code and same assumptions. It is shown that though the performance of the presently designed systems differ, and not always correspond to expected performance, achieving required performance in the future collider is feasible. Furthe, post-TRC plans of the Collimation task Force are discussed as well


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    Operation with colliding beams at PEP-II has progressed remarkably well with over half the design specific luminosity and 5:2 10 32 cm,2s,1 in multiple bunches demonstrated during the last commissioning period before installation of the BABAR detector. Further luminosity increases are anticipated as the vertical beam size is reduced and beam currents are raised towards design values. At high currents interesting multibunch dynamics, which depend strongly on current distribution, have been observed during single-beam commissioning studies. Transverse beam instabilities nominally controlled using bunch-by-bunch feedback were observed to be significantly suppressed, in the absence of feedback, with beams in collision.

    A high resolution wire scanner for micron-size profile measurements at the SLC

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    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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28112/1/0000561.pd

    Measurement of the Branching Fraction for B- --> D0 K*-

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    We present a measurement of the branching fraction for the decay B- --> D0 K*- using a sample of approximately 86 million BBbar pairs collected by the BaBar detector from e+e- collisions near the Y(4S) resonance. The D0 is detected through its decays to K- pi+, K- pi+ pi0 and K- pi+ pi- pi+, and the K*- through its decay to K0S pi-. We measure the branching fraction to be B.F.(B- --> D0 K*-)= (6.3 +/- 0.7(stat.) +/- 0.5(syst.)) x 10^{-4}.Comment: 7 pages, 1 postscript figure, submitted to Phys. Rev. D (Rapid Communications
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