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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The performance of the Fermilab Tevatron Collider at the commencement of run Ib was far below expectations. After a frustrating period of several months, a low-[beta] quad downstream of the interaction point at B0 was found to be rolled. This rolled quadrupole coupled the horizontal and vertical motion of the Tevatron beams. It also made matching the beam from the Main Ring to the Tevatron impossible, resulting in emittance blow up on injection. The net result of the roll was a significant reduction in the Tevatron luminosity. When the roll in the quadrupole was corrected the performance of the Tevatron improved dramatically. This note will discuss the experimental data indicating the presence of coupling and subsequent calculations which show how coupling an affect the luminosity. It is not intended to exhaust a discussion of coupling, which hopefully will be understood well enough to be discussed in a subsequent note.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The performance of the Fermilab Tevatron Collider at the commencement of run Ib was far below expectations. After a frustrating period of several months, a low-[beta] quad downstream of the interaction point at B0 was found to be rolled. This rolled quadrupole coupled the horizontal and vertical motion of the Tevatron beams. It also made matching the beam from the Main Ring to the Tevatron impossible, resulting in emittance blow up on injection. The net result of the roll was a significant reduction in the Tevatron luminosity. When the roll in the quadrupole was corrected the performance of the Tevatron improved dramatically. This note will discuss the experimental data indicating the presence of coupling and subsequent calculations which show how coupling an affect the luminosity. It is not intended to exhaust a discussion of coupling, which hopefully will be understood well enough to be discussed in a subsequent note.
Author: D. A. Edwards Publisher: ISBN: Category : Languages : en Pages : 3
Book Description
During the beginning of Run II of the Tevatron Collider it became apparent that a large skew quadrupole source, or sources, had developed in the superconducting synchrotron. Efforts to locate the current source of coupling were undertaken, with the eventual discovery that the main magnets had developed a systematic skew quadrupole moment over their lifetime. Over the past year, the magnets have been altered in place in an attempt to restore the systematic skew quadrupole moment to zero. Beam observations and their interpretations are presented, and remedial measures are discussed.
Author: J. Carson Publisher: ISBN: Category : Languages : en Pages : 9
Book Description
The Tevatron was designed with an extensive set of correction and adjustment magnets built into the spool pieces in recognition of the circumstance that a superconducting synchrotron was not as easy to modify as its conventional forebearers. Recently, concern has mounted at the high excitation of the skew quadrupole correctors. The purpose of this note is to account for this situation. When slow extraction was attempted from the Main Ring in the summer of 1970 horizontal-vertical coupling prevented adequate transverse oscillation growth for efficient slow spill. This situation was corrected by an 8 mrad roll of each of twelve equi-spaced quadrupoles [1]. In order to avoid a repetition of this problem in the Tevatron, an extremely strong skew quadrupole circuit was built in at the outset. When the Tevatron was commissioned only 4$ of the capability of this circuit was required. Now, 20 years later, the excitation of this skew quadrupole circuit is approximately 60%. Other skew quadrupole correctors were installed in the neighborhood of the long straight sections, and for a variety of reasons the number of elements in the strong circuit was reduced from 48 to 42. These are relatively minor changes in the present context. Recall that in the normal Tevatron tuning process the skew quad circuits are adjusted to minimize the difference between the horizontal and vertical tunes to the level of {Delta}{nu}{sub min} {approx} 0.003. Normally the horizontal-vertical coupling is not observed directly by orbit measurements during this procedure. it was recognized that the strength of the skew quadrupole settings would imply an uncorrected minimum tune difference of 0.2 units. Clearly, with the skew quad circuit turned off the coupling of the orbital motion should be easily observable. In the following sections, the authors describe the recent Tevatron studies that exhibit the transverse coupling and the analyses that link these observations to the long term development of a skew quadrupole coefficient in the Tevatron dipoles. In brief, their conclusion is that a{sub 1} at the level of one of the traditional units will account for the coupling and is consistent with physical examination of a selection of dipoles in the tunnel.
Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
The processes p{bar p} → l{bar {nu}}{sub?} + X and p{bar p} → ll−{sub?} + X (l = e,?) have been observed using the DO detector at the Fermilab Tevatron Collider at √s = 1.8 TeV. The observed signals in the electron and muon decay channels are used as a probe of the WW?, ZZ?, and Z?? vertex couplings. By comparing the event rates and shapes of the photon ET distributions with theoretical predictions, 95% confidence limits are obtained on the WW?, ZZ?, and Z{gamma}{gamma} vertex coupling parameters.
Author: Publisher: ISBN: Category : Languages : en Pages : 10
Book Description
Increased demand for higher luminosities from Fermilab proton-antiproton collider requires higher intensities and increased number of bunches. The performance of existing 6 x 6 and the proposed 36 x 36 collider is often limited by the non-linear effects arising from beam-beam interactions, in particular for high intensity beams. The tune shifts and spread from increased long range interactions combined with higher order multipoles complicates the frequency spectrum of the particle motions. TEAPOT simulation program is used to generate turn by turn data that could be used in the nonlinear mode spectrums analysis. Bispectral mode analysis is discussed.
Author: Y. Alexahin Publisher: ISBN: Category : Languages : en Pages : 3
Book Description
The Fourier analysis of Turn by Turn (TBT) data provides valuable information about the machine linear and non-linear optics. A program for the measurement and correction of the linear coupling based on the TBT data analysis has been integrated in the TEVATRON control system. The new method is fast, allows the measurement of the coupling during acceleration and offers information about the sum coupling coefficient and the location of the sources of coupling.
Author: Vladimir Shiltsev Publisher: ISBN: Category : Languages : en Pages : 3
Book Description
Chromaticity drift is a well-known and more or less well-understood phenomenon in superconducting colliders such as the Tevatron. Less known is the effect of tune and coupling drift, also observed in the Tevatron during injection. These effects are caused by field drifts in the superconducting magnets. Controlling the behavior of the tune, coupling, and chromaticity is an important part of reducing beam loss at injection and at the start of the Tevatron ramp. In this context we conducted several beam-studies during the period of April to August 2004 in which we measured the drift in the Tevatron chromaticity, tunes, and coupling during the injection porch. In some cases we also measured the snapback at the start of the ramp. We will present the results of these studies data and put them into context of the results of off-line magnetic measurements conducted in spare Tevatron dipoles.
Author: V. Sajaev Publisher: ISBN: Category : Languages : en Pages : 6
Book Description
The optics measurements have played important role in improving the performance of Tevatron collider. Until recently, most of them were based on the differential orbit measurements with data analysis, which neglects measurement inaccuracies such as differences in differential responses of beam position monitors, their rolls, etc. To address these complications we have used a method based on the analysis of many differential orbits. That creates the redundancy in the data allowing to get more detailed understanding of the machine. In this article we discuss the progress with Tevatron optics correction, its present status and future improvements.
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Author: D. A. Edwards
Author: J. Carson
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Author: Y. Alexahin
Author: Christina Mesropian
Author: Vladimir Shiltsev
Author: V. Sajaev