800 research outputs found
Detection of coherent beam-beam modes with digitized beam position monitor signals
A system for bunch-by-bunch detection of transverse proton and antiproton
coherent oscillations in the Fermilab Tevatron collider is described. It is
based on the signal from a single beam-position monitor located in a region of
the ring with large amplitude functions. The signal is digitized over a large
number of turns and Fourier-analyzed offline with a dedicated algorithm. To
enhance the signal, band-limited noise is applied to the beam for about 1 s.
This excitation does not adversely affect the circulating beams even at high
luminosities. The device has a response time of a few seconds, a frequency
resolution of in fractional tune, and it is sensitive to
oscillation amplitudes of 60 nm. It complements Schottky detectors as a
diagnostic tool for tunes, tune spreads, and beam-beam effects. Measurements of
coherent mode spectra are presented and compared with models of beam-beam
oscillations.Comment: 7 pages, 4 figures. Submitted to the Proceedings of the ICFA
Mini-Workshop on Beam-beam Effects in Hadron Colliders (BB2013), Geneva,
Switzerland, 18-22 March 201
Collimation with hollow electron beams
A novel concept of controlled halo removal for intense high-energy beams in
storage rings and colliders is presented. It is based on the interaction of the
circulating beam with a 5-keV, magnetically confined, pulsed hollow electron
beam in a 2-m-long section of the ring. The electrons enclose the circulating
beam, kicking halo particles transversely and leaving the beam core
unperturbed. By acting as a tunable diffusion enhancer and not as a hard
aperture limitation, the hollow electron beam collimator extends conventional
collimation systems beyond the intensity limits imposed by tolerable losses.
The concept was tested experimentally at the Fermilab Tevatron
proton-antiproton collider. The first results on the collimation of 980-GeV
antiprotons are presented.Comment: 4 pages, 5 figure
Tevatron Beam Halo Collimation System: Design, Operational Experience and New Methods
Collimation of proton and antiproton beams in the Tevatron collider is
required to protect CDF and D0 detectors and minimize their background rates,
to keep irradiation of superconducting magnets under control, to maintain
long-term operational reliability, and to reduce the impact of beam-induced
radiation on the environment. In this article we briefly describe the design,
practical implementation and performance of the collider collimation system,
methods to control transverse and longitudinal beam halo and two novel
collimation techniques tested in the Tevatron.Comment: 25 p
E835 at FNAL: Charmonium Spectroscopy in Annihilations
I present preliminary results on the search for in its
and decay modes. We observe an excess of \eta_c\gamma{\cal P} \sim 0.001M=3525.8 \pm 0.2 \pm 0.2
\Gamma\leq10.6\pm 3.7\pm3.4(br) <
\Gamma_{\bar{p}p}B_{\eta_c\gamma} < 12.8\pm 4.8\pm4.5(br) J/\psi\pi^0$ mode.Comment: Presented at the 6th International Conference on Hyperons, Charm and
Beauty Hadrons (BEACH 2004), Chicago(Il), June 27-July 3,200
Interference Study of the chi_c0 (1^3P_0) in the Reaction Proton-Antiproton -> pi^0 pi^0
Fermilab experiment E835 has observed proton-antiproton annihilation
production of the charmonium state chi_c0 and its subsequent decay into pi^0
pi^0. Although the resonant amplitude is an order of magnitude smaller than
that of the non-resonant continuum production of pi^0 pi^0, an enhanced
interference signal is evident. A partial wave expansion is used to extract
physics parameters. The amplitudes J=0 and 2, of comparable strength, dominate
the expansion. Both are accessed by L=1 in the entrance proton-antiproton
channel. The product of the input and output branching fractions is determined
to be B(pbar p -> chi_c0) x B(chi_c0 -> pi^0 pi^0)= (5.09 +- 0.81 +- 0.25) x
10^-7.Comment: 4 pages, 4 figures, Accepted by PRL (July 2003
- …