1. ECLOUD04, Panel Discussion, April 2004F. Zimmermann Panel Discussion future machines: higher intensity shorter bunch spacings and/or higher charge per bunch electron cloud! CERN activities focus on LHC & CLIC simulation need & proposed experiments international collaborations

2. ECLOUD04, Panel Discussion, April 2004F. Zimmermann Observed Electron Cloud Threshold vs. Bunch Spacing Future & Proposed Machines SPS, PS, Tevatron, APS thresholds are all similar DAFNE and KEKB look better, RHIC worse extrapolation to shorter spacings?

3. ECLOUD04, Panel Discussion, April 2004F. Zimmermann Hot topics for LHC (and others): long-time survival of electrons elastic reflection at low energy, trapping in magnetic fields,… electron cloud in cold environment efficiency of scrubbing minimum secondary emission yield that can be reached & sustained, scrubbing time required, effect of temperature and magnetic field, vacuum pressure beam stability & long-term emittance growth could set >10 times tighter limit on acceptable e-cloud than heat load stabilizing measures, optimized beam parameters benchmarking simulations with experiments in the SPS (RHIC? B factories?) SPS experiments and simulations improved simulations, SPS experiments planned activities

4. ECLOUD04, Panel Discussion, April 2004F. Zimmermann Hot topics for CLIC (and others): electron cloud for short spacing with significant synchrotron radiation impact on equilibrium emittance trapping in wiggler field efficiency & side-effects of countermeasures e.g., coating, clearing electrodes or clearing fields, antechambers, octupoles, chromaticity, feedback, operation below threshold or in Sam Heifet’s high current regime simulation discrepancies for B factories halo generation effect on IP spot size

5. ECLOUD04, Panel Discussion, April 2004F. Zimmermann one important simulation need reliable prediction of long-term emittance growth for the LHC: include lattice variation around the ring consider discontinuous e-cloud regions better interface or combination of build-up and instability simulations (realistic electron distribution, response of electron cloud to instability, etc.) adequate & correct boundary conditions (magnetic boundaries? actual apertures) inclusion of space charge, impedances, beam-beam, feedback, chromaticity, etc. benchmarking in experiments

6. ECLOUD04, Panel Discussion, April 2004F. Zimmermann proposed experiments at other labs explore electron cloud occurrence in the cold sections of RHIC and/or the Tevatron in view of LHC commissioning study the dependence of e - density & emittance blow up on (shorter) bunch spacing at KEKB and PEP-II LER in view of demonstrating LC feasibility investigate the effect of wiggler on e - build up in PEP-II (KEKB study already done) study predicted solenoid resonance at PEP-II analyze pieces of PEP-II/KEKB chamber to understand (in)efficiency of coating or scrubbing apply coating & test clearing electrodes at the ATF

7. ECLOUD04, Panel Discussion, April 2004F. Zimmermann strong multipacting in a clean TiN coated Al chamber, without solenoid, after 7 years of PEP-II operation!? w/o solenoid with solenoid 2 A beam current e - signal (A. Kulikov)

8. ECLOUD04, Panel Discussion, April 2004F. Zimmermann European Steering Group on Accelerator R&D (ESGARD) [CEA, CERN, CNRS-Orsay, DESY, INFN-LNF, etc.] http://esgard.lal.in2p3.fr/http://esgard.lal.in2p3.fr/ Within the SIXTH FRAMEWORK PROGRAMME of the EUROPEAN UNION Coordinated Accelerator Research in Europe (CARE) 3 Networking & 4 Joint Research Activities Addressing Electron Cloud: N2: Electron Linear Accelerator Network (ELAN); TESLA and CLIC (Deputy Coordinator D. Schulte) N4: High Energy High Intensity Hadron Beams (HEHIHB); SuperLHC, VLHC (Coordinator: F. Ruggiero; Deputy Coordinator for HEHIHB WP3: F. Zimmermann) “...electron cloud… codes need comparisons and benchmarking by beam measurements and are of common interest for high-luminosity hadron colliders and high-intensity synchrotrons… …establish a working infrastructure in Europe parallel to the proposed US-LARP programme, which has as objective to streamline R&D work in the 3 big national labs in the US with the additional benefit of contributing to LHC upgrade studies. A parallel US-LARP and CARE approach would facilitate further the important information flow and worldwide collaboration efforts.” [excerpt from N4 WP3 proposal]

9. ECLOUD04, Panel Discussion, April 2004F. Zimmermann Country Number of institutes Number of persons France29 Germany526 Italy720 Japan16 Netherlands15 Poland12 Spain13 Sweden13 Switzerland24 United Kingdom13 U.S.A.325 Russia24 CERN133 Participants to the CARE N4 Activities: (other collaborations that could address e-cloud exist, e.g.,Int’l ATF Collaboration)

10. ECLOUD04, Panel Discussion, April 2004F. Zimmermann Review and Comparison of Simulation Codes Modeling Electron-Cloud Build Up and Instabilities E. Benedetto, F. Ruggiero, D. Schulte, F. Zimmermann, CERN; G. Rumolo, GSI, J. Bellodi, RAL; K. Ohmi, S.S. Win, KEK; A. Ghalam, T. Katsouleas, USC; V. Decyk, W. Mori, UCLA; M. Furman, LBNL; Y. Cai, M. Pivi, SLAC; M. Blaskiewicz, L. Wang, BNL; … “Several computer codes written at various laboratories are employed for modeling the generation and the consequences of an electron cloud. We review the most popular of these programs, which simulate either the build of an electron cloud or the instabilities it produces, and we compare simulation results for identical, or similar, input parameters obtained from the various codes.” Joint abstract on code comparisons submitted to EPAC’2004 other contributors welcome!!