Wolfgang Schnell

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Considerable transverse focusing power can be obtained from the high-gradient RF accelerating structure of a linear collider by making either the aperture or the main cell geometry asymmetric. Such structures, acting as microwave quadrupoles, can be used to stabilize transverse wakefields by creating a spread in the transverse oscillation frequencies of the(More)
The RF cavities employed for stacking in the ISR are equipped with a powerful feedback system, which compensates for most of the beam-induced voltage. This system is, however, limited - mainly by the current in the final amplifier tube - to injected beam intensities of about 5 × 1012 protons at most. Higher intensities are now available from the PS.(More)
Early in 1976 a study group at CERN began to examine design concepts for a Large Electron-Positron storage ring, LEP. At that time, 50 km circumference and 100 GeV per beam - to be obtained with a conventional radio frequency system - were chosen. This first study was terminated with several problems still unsolved, including extreme sensitivity of orbit(More)
The effect of phase noise on a tightly bunched proton beam is investigated taking into account the frequency spread in the beam, the wall impedance and the phase feedback loop. Under normal conditions the measured dilution rates in the ISR correspond typically to a doubling of the bunch length in one to a few hours, and are consistent with the measured(More)
A conceptual design of a 100 GeV e+-e- storage ring (LEP) being studied at CERN and some of the problems encountered are presented. The 20 GeV fastcycling injector synchrotron is studied at the Rutherford Laboratory.1 To obtain a luminosity L = 1 × 1032 cm-2 s-1 at 100 GeV, the product of bending radius ¿ and the RF power PB delivered to both beams must be(More)
During 1974, the period covered by this report, the ISR were in operation for 3500 h, of which 80% were for physics runs and their preparation. 20 physics experiments took data at six of the beam intersections. Ten of these experiments were completed. Several new ones will start this year, after the annual shut-down ending March 1st. Again six intersections(More)
Introduction Functional magnetic resonance imaging (fMRI) is able to detect active areas in brain. This imaging method is demanding on the MR scanner’s radio frequency (RF) and gradient stability and a signal-to-noise ratio (SNR) of the acquired images since the detected signal changes are quite small [1]. Therefore, the noise and stability contribution of(More)
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