1. Agenda Today: CesrTA and SuperKEKB simulations - Ohmi
Updates on photoe- estimates by Synrad3D - Laura
CesrTA last run and updates on mitigations - Mark
Mitigations recommendation and WG plans - Mauro

2. Recommendation for electron cloud mitigations in the DR
LC DR Electron Cloud Working Group
July 22, 2010
ILC DR Webex Meeting

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

4. Build up simulations Ongoing: In 3km ring, run with 3ns bunch spacing
Miguel, Theo and Lanfa are running simulations to compare with
previous 6ns spacing results
Then: including refined estimate of photoelectron production rate by SYNRAD3D with reflectivity and next with antechambers.
Laura, Kathy and Gerry are working on estimates for the ILC Damping Ring.

5. Recommendation for Mitigations
Need to evaluate mitigations for all the DR regions.
Need to start the discussion on criteria for the selection and on alternatives for the mitigation.
Propose to use the “Analytic Hierarchical Process” to focus on the multi-element analysis and for decision making:
Decompose the problem into a hierarchy of sub-problems, criteria and alternatives
Systematically evaluate its various elements by comparing them to one another two at a time (core of the analysis)
The decision makers can use concrete data about the elements, or their judgments about the elements' relative meaning and importance.

6. Recommendation for Mitigations
Essence of the AHP is that expert’s judgments, and not just the underlying information, can be used in performing the evaluations.
A numerical weight is derived for each element of the hierarchy, allowing diverse elements to be compared to one another in a rational and consistent way.
In the final step of the process, numerical priorities are calculated for each of the decision alternatives.
The hope is that this method is a good way to trigger discussions, focus on each aspect of the problem and take a decision based on the judgment of the Working Group as a whole.

7. Mitigations Table for ILC Damping Ring
DR element
% ring
Antechamber need
Coating
Mitigation
Additional Mitigation
DRIFT in STRAIGHT 54 No
Solenoid
DRIFT in ARC 33
Downstream of BEND only
BEND 7
Yes
WIGG 3
QUAD &
SEXT
Downstream BEND / WIGG
Color code: Green = defined, Red = not yet defined.
Goal is to define mitigations by 2010 or early 2011 as input for ILC TD Phase 2. 7

8. Select Mitigations for DRIFTs in long STRAIGHTs

9. Scale for Pairwise Comparison

10. Select Mitigations for DRIFTs in long STRAIGHTs

11. Groove chambers in DRIFT section
Installation of groove chambers in PEP-II
Grooves chamber in PEP-II DRIFT section

12. Rectangular groove Low impedance with round tips
There is a small impedance enhancement factor for a larger t/p (K.Bane and Stupakov slac-pub-11677)
p=1.25mm (period)
d=2.5mm (depth)
t=0.125mm (thickness)
p=1.25mm
d=2.5mm
t=0.25mm
p=1.25mm
d=3.5mm
t=0.125mm
Round tips

13. Mitigations Table for ILC Damping Ring
DR element
% ring
Antechamber need
Coating
Mitigation
Additional Mitigation
DRIFT in STRAIGHT 54 No
NEG
Solenoid
Grooves
DRIFT in ARC 33
Downstream of BEND only
BEND 7
Yes
TiN
WIGG 3
Clearing Electrodes
QUAD &
SEXT
Downstream BEND / WIGG
Color code: Green = defined, Red = not yet defined.
Goal is to define mitigations by 2010 or early 2011 as input for ILC TD Phase 2. 13

14. Report Document on Mitigations and Recommendation for ILC DR
A document produced by the Working Group by late 2010 early 2011, including: the research work, the recommendation on mitigations, the recommendation process and a clear set of criteriae that lead to the recommendation.

15. Report Document on Mitigations and Recommendation for ILC DR

16. WebEx meeting Proposed time Next Webex meeting:
Wednesday 25 August 2010
Propose to have separate Webex meetings with interested colleagues to go over the Analytic Hierarchycal Process and cover all the DR sections

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

18. Messages board
Blackboard
Messages here