Florian Zimmermann

Learn More
014801-1 Present and future accelerators’ performances may be limited by the electron cloud (EC) effect. The EC formation and evolution are determined by the wall-surface properties of the accelerator vacuum chamber. We present measurements of the total secondary electron yield (SEY) and the related energy distribution curves of the secondary electrons as a(More)
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)
The computer program LIAR (”LInear Accelerator Research code”) is a numerical simulation and tracking program for linear colliders. The LIAR project was started at SLAC in August 1995 in order to provide a computing and simulation tool that specifically adresses the needs of high energy linear colliders. LIAR is designed to be used for a variety of(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)
This note describes the program HEADTAIL for the simulation of transverse and longitudinal single bunch phenomena, with special emphasis on the instability and emittance growth induced by an electron cloud. All input parameters as well as the standard output files are described here. The note is intended to provide potential users with the guidelines for(More)
Correlation Neglect in Belief Formation Many information structures generate correlated rather than mutually independent signals, the news media being a prime example. This paper shows experimentally that in such contexts many people neglect these correlations in the updating process and treat correlated information as independent. In consequence, people’s(More)
In positron and proton storage rings, electrons produced by photoemission, ionization, and secondary emission accumulate in the vacuum chamber during multibunch operation with close spacing. A positron or proton bunch passing through this "electron cloud" experiences a force similar to a short-range wake field. This effective wake field can cause a(More)
At the Stanford Linear Collider (SLC), the interactionpoint spot size is minimized by repeatedly correcting, for both beams, various low-order optical aberrations, such as dispersion, waist position or coupling. These corrections are performed about every 8 hours, by minimizing the IP spot size while exciting different orthogonal combinations of final-focus(More)
This note describes the use of the program ECloud for the simulation of the electron cloud build up, which occurs due to photoemission, ionization, and secondary emission inside an accelerator beam pipe during the passage of a narrowly spaced proton or positron bunch train. All input parameters as well as the standard output files are explained. The goal of(More)