| Paper | Title | Page |
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| THPAN115 | Direct Measurements of Beta-star in the Tevatron | 3495 |
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Funding: Work supported by the U. S. Department of Energy under contract No. DE-AC02-76CH03000. Until recently, values of the amplitude functions through the Interaction Regions of the Tevatron collider detectors have been inferred either by reconstructing event locations through the detector and mapping out the luminous region to deduce the beam emittance and amplitude function or by performing differential closed orbit measurements while varying steering magnets and producing detailed models of the synchrotron's optical properties which reproduce the observed orbital deviations. Both of these methods rely on often lengthy off-line analyses and sometimes many hours of experimental data to obtain a meaningful result. The new Tevatron Beam Position Monitor system, commissioned in 2005, has allowed unprecedented detail of turn-by-turn motion to be measured at the 20-micron level and for thousands of beam revolutions. Such measurements performed with a freely oscillating proton beam, excited by a kicker magnet, allow for the direct measurement of the amplitude function which is model independent. A simple measurement procedure, data analysis method, and typical results for the Tevatron experimental regions are presented. |
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| THPAN102 | Tevatron Optics Measurements using an AC Dipole | 3465 |
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| The AC dipole is a device that can be used to study beam optics of hadron synchrotrons. It can produce sustained large amplitude oscillations with virtually no emittance growth. A vertical AC dipole for the Tevatron was recently implemented and a maximum oscillation amplitude of 2 (4) σ beam size at 980 (150) GeV was achieved. If such large oscillations are combined with the Tevatron's BPM system (20 micron resolution), not only linear but even nonlinear optics can be measured not depending on machine models. This paper discusses how to make model independent measurements of ring-wide beta functions using the AC dipole and shows test results and comparisons to other methods. The emittance preserving nature of the AC dipole allows multiple measurements on the same beam. By repeating measurements with a small change to the optics every time, the accuracy of measurements using the AC dipole can be determined. Results of such tests are also presented. | ||
| FRPMS004 | Geometrical Interpretation of Nonlinearities from a Cylindrical Pick-up | 3862 |
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| In many accelerators, cylindrical pick-ups are used to measure transverse beam position. Although theoretically signals from these pick-ups are related to infinite power series of the beam position, in practice only finite number of terms are considered. Hence, the position measurements degrade when the beam position is far from the center of the pick-up. This paper shows that the power series of the beam position signal actually converges into a compact form with simple geometrical interpretation. It is then proven that with help of these geometrical relations the beam position can be expressed as a compact function of pick-up signals which includes infinite order of nonlinearities. The paper is concluded with a simple test of nonlinearities in signals using pick-ups of the Tevatron and numerical simulations to suggest a possible practical usage of this infinite order expression. | ||
| FRPMS005 | The Tevatron AC Dipole System | 3868 |
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| The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without causing emittance growth. This makes it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high-power audio amplifier since its operating frequency is approximately 20 kHz. The low impedance magnet is incorporated into a parallel resonant system to form an 8 Ω equivalent circuit to maximize the power output of the amplifier. The magnet used is a vertical pinger previously installed in the Tevatron making the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-σ beam size were achieved at 980 GeV. The paper discusses details of the resonant circuit. It also shows test results of the system both on the bench and with the beam. |