Phys. Rev. Lett. Phys. Rev. Lett. 0031-9007 Can low energy electrons affect high energy physics accelerators? Cimino R LNF-INFN, Frascati CERN Collins I R CERN Furman M A LBNL, Berkeley Pivi M SLAC Stanford Ruggiero F CERN Rumolo Giovanni GSI, Darmstadt Zimmermann Frank CERN 2004 93 014801/1 4 The properties of the electrons participating in the build up of an electron cloud (EC) inside the beam-pipe have become an increasingly important issue for present and future accelerators whose performance may be limited by this effect. The EC formation and evolution are determined by the wall-surface properties of the accelerator vacuum chamber. Thus, the accurate modeling of these surface properties is an indispensible input to simulation codes aimed at the correct prediction of build-up thresholds, electron-induced instability or EC heat load. In this letter, we present the results of surface measurements performed on a prototype of the beam screen adopted for the Large Hadron Collider (LHC), which presently is under construction at CERN. We have measured the total secondary electron yield (SEY) as well as the related energy distribution curves (EDC) of the secondary electrons as a function of incident electron energy. Attention has been paid, for the first time in this context, to the probability at which low-energy electrons (< 20 eV) impacting on the wall create secondaries or are elastically reflected. It is shown that the ratio of reflected to true-secondary electrons increases for decreasing energy and that the SEY approaches unity in the limit of zero primary electron energy. research-article

Closed orbit response to quadruple strength variation Wolski A Zimmermann Frank 2004 We derive two formulae relating the variation in closed orbit in a storage ring to variations in quadrupole strength, neglecting nonlinear and dispersive effects. These formulae correct results previously reported [1,2,3]. We compare the results of the formulae applied to the ATF with simulations using MAD, and consider their application to beam-based alignment. PREPRINT

Contributions to the 30th Advanced ICFA Beam Dynamics Workshop on High Luminosity e+e- Collisions "FACTORIES'03" SLAC, Stanford, 13-16 October 2003 Zimmermann Frank Koutchouk Jean-Pierre Wenninger J 2004 Contributions to the 30th Advanced ICFA Beam Dynamics Workshop on High Luminosity e+e- Collisions " FACTORIES 03", SLAC, Stanford, 13-16 October 2003. Contents: 1.Summary of the Working Group on IR Design, Beam-Beam Interaction and Optics (F. Zimmermann) 2. Brief Review of Super-Bunches for Hadron Colliders (F. Zimmermann) 3. Raimond-Seryi Final Focus for e+e- Factories? (F. Zimmermann) 4. Weak-Strong Model for the Combined Effect of Beam-Beam Interaction and Electron Cloud (F. Zimmermann) 5. Compensating Parasitic Collisions Using Electromagnetic Lenses (J.-P. Koutchouk, J. Wenninger, F. Zimmermann) PREPRINT

Potential of non-standard emittance damping schemes for linear colliders Braun Hans Heinrich CERN Korostelev M S CERN Zimmermann Frank CERN 2004 We estimate the potential of various non-standard schemes for producing low-emittance electron/positron beams in a linear collider and compare their projected performance with that achieved by the present design of the CLIC damping ring. The options considered include the use of rf-wigglers and the integration of radiation damping into the linac CLINOT

Phys. Rev. Spec. Top. Accel. Beams Phys. Rev. Spec. Top. Accel. Beams Resistive-wall wake and impedance for non-ultrarelativistic beams Zimmermann Frank CERN Oide K 2004 7 The usual formulae for the resistive-wall wake field are derived considering ultra-relativistic beams, travelling at the speed of light. This simplifies the calculation, and it leads to a cancellation between electric and magnetic fields. However, for proton beams below 10 GeV and for many heavy ion beams, the velocities may significantly differ from the speed of light. In this paper, we compute the longitudinal and transverse wake fields for velocities smaller than c, and examine under which conditions non-relativistic effects become important. We illustrate our results by a few examples. research-article

Study of Long-range Collisions and Wire Compensation for Tevatron Run-II Zimmermann Frank CERN Sen T Erdelyi B Boocha V 2004 This report summarizes studies of long-range collisions and their compensation by current carrying wires for the Tevatron Run-II, which were performed during a two-week stay at Fermilab, February 22 to March 8, 2004. The weak-strong code WSDIFF was significantly extended to simulate the actual long-range encounters at the Tevatron for different antiproton bunches in the train at injection and in collision. Tune footprints and diffusive apertures simulated by this code are presented for various cases, differing in the bunch position, the energy, the number of long-range and head-on collisions, the presence of additional compensating wires and the momentum deviation. It is confirmed that the solution of 4 wires for injection, previously found by B. Erdelyi, raises the dynamic aperture, by about 1.0-1.5sigma. For both injection and collision an ideal compensation of the 6 or 3 closest long-range encounters was modeled, by removing these collisions altogether. At collision, an improvement in the dynamic aperture of the order of 0.5-1.0sigma is found. The much more copious residual long-range collisions are shown to also strongly affect the diffusive aperture, however, which highlights a lack of correlation between dynamic aperture and tune footprints. The dynamic aperture widely varies with the bunch number, ranging from 5 to 8sigma; along the train, in collision for on-momentum particles. Analytical calculations of tune shift, coupling, chromaticity and chromatic coupling similarly reveal a large variation from bunch to bunch, amounting to 16 units in chromaticity and 4 or 5 units in chromatic coupling. Achieving compensation for all bunches in the train appears a nontrivial challenge for dc wires, in particular if off-energy is also to be corrected. In a machine study on March 1, the Tevatron electron lens was used to simulate a wire and the dependences of beam lifetime, tune, emittances and bunch length on the beam-TEL distance were explored. The results of this experiment are reported elsewhere [1]. PREPRINT