Measurement of the Vertical Emittance and beta-Function at the PEP-II Interaction Point Using the BaBar Detector

We present measurements of the effective vertical emittance and IP {beta}-function in the PEP-II asymmetric B Factory at SLAC. These beam parameters are extracted from fits to the longitudinal dependence of the luminosity and the vertical luminous size, measured using e{sup +}e{sup -} {yields} {mu}{sup +}{mu}{sup -} events recorded in the BABAR detector. The results are compared, for different sets of machine conditions, to accelerator-based measurements of the optical functions of the two beams

Microstructures Manufactured in Diamond by Use of Laser Micromachining.

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

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

Closed Orbit Distortion and the Beam-Beam Interaction

We study the applicability of beam-beam deflection techniques as a tuning tool for the SLAC/LBL/LLNL B factory, PEP-II. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, we calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the IP, provide distinct coordinate- or frequency-space signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed

MULTIPLE HIGH CURRENT BUNCHES IN PEP-II

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

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*-

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