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

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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. Hierarchical table for Mitigations Selection Process

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

11. Our presentations posted on web site
ILC Damping Ring Wiki:
ILC Damping Ring Teleconference page:

12. Messages board
Blackboard
Messages here