ILC WP3 Task Force 6
contributors: K. Ohmi (KEK), M. Pivi (SLAC), C. Vaccarezza (INFN), L. Wang (SLAC), R. Wanzenberg (DESY), D. Xaowei (KEK), Guoxing Xia (DESY), F. Zimmermann (CERN) + anybody else interested
coordinators: K. Ohmi (KEK), M. Pivi (SLAC), F. Zimmermann (CERN)
Draft: 22 June 2005
Aims
A baseline configuration for the ILC will be selected by the end of 2005. The electron-cloud effects are among the criteria to be considered when choosing the circumference, bunch charge and bunch spacing, chamber apertures, wiggler design, antechambers, photon stops, clearing electrodes etc.
Methodology
1) Pertinent parameters for three different rings (17 km, 6 km and 3 km circumference) will be compiled, including beam size in arcs, wiggler, and straights, bunch spacing, tunes, average beta functions, tunes, chamber dimensions, magnetic fields;
2) Electron cloud build is simulated for the different regions (arcs, wigglers, straights) in the three rings, considering various sets of beam parameters and secondary emission yields.
3) For the wiggler simulations the field can be modeled at various levels of sophistication, and the importance of refined models has to be explored.
4) Single-bunch wake fields and the thresholds of the fast single-bunch TMCI-like instability are estimated either in simulations or analytically by averaging over the different regions of the ring;
5) Multi-bunch wake fields and growth rates are inferred from e-cloud build up simulations or from dedicated multi-bunch simulation codes;
6) Electron induced tune shifts will be calculated and compared;
7) Predictions of electron build up from different simulation codes are compared;
8) Implemented in the simulations will be countermeasures which may be proposed as the ILC DR design evolves.
Expressions of interest and available tools
Build-up simulation codes are PEI (KEK), POSINST (LBNL/SLAC), ECLOUD (CERN), and CLOUDLAND (BNL/SLAC). Instability simulation codes are PEHTS (KEK) and HEADTAIL (CERN) for single-bunch instabilities, and PEI-M for multi-bunch instabilities (KEK). Multi-bunch wake fields can be extracted from POSINST and ECLOUD. There also exists a single-bunch instability code ECI written by Y. Cai at SLAC. DESY, INFN, and CERN are collaborating in the EUROTeV WP3 ECLOUD subtask, the goals of which overlap with the ILC WG3 ‘electron-cloud’ task. Rainer Wanzenberg (DESY) has started a compilation of ring and beam parameters. Further contributions are highly welcome!
Comparisons with existing machines
A benchmarking program is ongoing at the CERN SPS and at DAFNE, in addition to PSR, PEP-II and KEKB, and can support the predictions.
Phone Conferences & Other Meetings
Phone conference 19.07.2005, Mauro Pivi, Frank Zimmerman, Xiaowei Dong, Mauro Pivi (II), minutes
Phone conference 10.08.2005, K. Ohmi, R. Macek, M. Pivi
Meeting at DESY, 12.09.2005, E. Elsen, Guoxing Xia, R. Wanzenberg, F. Zimmermann
LC DR Phone Meeting, 05.10.2005, M. Pivi
Literature & Material
Draft paper on DR vacuum system , A. Wolski & T. Kennedy
DR Megatables by A. Wolski
Beam Sizes OCS, Beam Sizes OTW, Beam Sizes TESLA by A. Wolski
DR Parameters used in Mauro Pivi's PAC paper
Talk at BDIR EUROTeV ELAN Meeting London, June 2005, by F. Zimmermann
EUROTeV WP3 Draft Plan for 2005/2006