Agenda Today: Electron cloud build-up in Wigglers – Theo Demma Electron cloud build-up in Quad and Sext – Lanfa Wang Mitigations recommendation discussion – all

Recommendation for electron cloud mitigations in the DR Mauro Pivi for the LC DR Working Group August 25, 2010 ILC DR Webex Meeting

WG Main Deliverables Characterization of electron cloud at different bunch spacing: 6ns and 3ns by end 2010 Recommendation for the baseline and alternate solutions for the electron cloud mitigation in various regions of the ILC Positron Damping Ring. by end 2010

Recommendation for Mitigations Evaluate mitigations for all the DR regions. Started discussion on criteria for the selection and on mitigation alternatives Mitigations evaluation process: With respect to the method shown at previous Webex meeting, some modifications: Simplified the method and reduced alternatives Ranking scales simplified (still linear though) Similarities with DRs recommendation process made in 2006 Hopefully clearer

Recommendation for Mitigations Going through one case GOAL: Select electron cloud mitigation in DRIFT sections for the DR Straights Criteria for mitigation evaluation: Efficacy of mitigation Impact on Vacuum Impact on Impedance/Optics Costs Criteria includes a number of sub-criteria. For example “Costs” includes: Design, Manufacturing, Durability & Maintenance costs, see below

Scale for Pairwise Comparison Intensity of Importance Ranking the Criteria To rank the criteria systematically, we compare them pairwise using a scale summarized as Scale for Pairwise Comparison Intensity of Importance Definition Explanation 1 Equal importance Two elements contribute equally to the objective 2 Moderate importance Experience and judgment slightly favor one element over another 3 Strong importance Experience and judgment strongly favor one element over another 4 Very Strong to Extreme Importance One element is favored very strong over another or the evidence favoring one element is of the highest possible order of affirmation

Evaluation of mitigation alternatives GOAL: Select electron cloud mitigation in DRIFT sections for the DR Straights Electron cloud mitigation Alternatives for DRIFTs in STRAIGHT sections: TiN or amorphous-Carbon NEG coating Grooves with coating Clearing Electrodes have not been considered here since they are costly and practically difficult to implement in DRIFTs and over long distances

Evaluation of mitigation alternatives TiN, C and NEG imply also the installation of solenoids To rank the alternatives, we compare them against each of the criteria using a scale from -4 to +4 summarized as: Negative values=detrimental 0 = no impact Positive values = helpful

Hierarchical table for Mitigations Selection Process

WebEx meeting Proposed date/Time for next Webex meeting: Wednesday 22 or 29 September 2010

Our presentations posted on web site ILC Damping Ring Wiki: https://wiki.lepp.cornell.edu/ilc/bin/view/Public/DampingRings/ ILC Damping Ring Teleconference page: https://wiki.lepp.cornell.edu/ilc/bin/view/Public/DampingRings/TeleConference

Messages board Blackboard Messages here