F’rank Zimmermann

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The electron cloud causes an increase in the vacuum pressure. It also induces slow multi-bunch and fast singlebunch instabilities, and, for the LHC, it significantly increases the heat load on the cryogenics system. This report describes our computer model of the electron cloud build up, presents simulation results for SPS and LHC, and investigates how the(More)
A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy(More)
Recent simulation results and some analytical estimates are presented on beam-induced multipacting in SPS, PS, and LHC. In particular, we discuss modifications to the secondary emission model, electron cloud build up simulated for various filling patterns, central cloud density, electron ‘pinch’ during the bunch passage, expected tune shifts and tune(More)
fin the beam pipe of the Large Hadron Collider (LHC), photoemission and secondary emission give rise to a quasistationary electron cloud, which is established after a few bunch passages. The response of this electron cloud to a transversely displaced bunch resembles a short-range wakefield and can cause a fast instability [l]. In addition, beam-induced(More)
For high luminosity in electron-positron linear colliders, it is essential to generate low vertical emittance beams. We report on the smallest vertical emittance achieved in single-bunch-mode operation of the Accelerator Test Facility, which satisfies the requirement of the x-band linear collider. The emittances were measured with a laser-wire beam-profile(More)
The term ‘electron cloud’ refers to an accumulation of electrons inside an accelerator beam pipe which is sufficiently strong to affect the accelerator operation, e.g., by causing beam loss, emittance growth, increase in the vacuum pressure, or degradation of the beam diagnostics. Primary electrons are generated by a number of processes. Their number can be(More)
This report reviews procedures and techniques for measuring, correcting and controlling various optics parameters of an accelerator, including the betatron tune, beta function, betatron coupling, dispersion, chromaticity, momentum compaction factor, and beam orbit. The techniques described are not only indispensable for the basic set-up of an accelerator,(More)
We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662 keV gamma photon energy and achieves a spatial image resolution of 0.2 line pairs/ mm at 10% modulation transfer function for noncollimated detectors. It is primarily intended for the scientific study of flow regimes and phase(More)
Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the(More)