WebEx meeting November 17, 2009 ILC Damping Ring Working Group on Electron Cloud LC e- cloud Working Group November 17, 2009

LC e- cloud Working Group AAP Request Request from Accelerator Advisory Panel (AAP) Review at TILC09: “The AAP would like to see a plan laid out showing how the damping ring group plans to arrive at a decision for the viability of the ILC damping ring choice with respect to electron- cloud immunity. A clear set of criteria for the vacuum system should be developed that will lead to the choice of a baseline solution..”

November 17, 2009 LC e- cloud Working Group AAP Recommendation “The AAP notes that … the impact of the e- cloud must be reevaluated for the 12 ns and 6 ns bunch spacings … with half the number of bunches in the 6-km configuration, i.e. 12 ns bunch spacing would operate in a safer regime with regard to electron cloud. Reducing the positron ring circumference to 3-km may risk losing this back-up solution.”

November 17, 2009 LC e- cloud Working Group Electron cloud working group Following the recommendation from the AAP Review this Working Group is set up: to define the work/resources needed for a reliable evaluation and assigns the tasks to the available resources. At the conclusion of the work the results will be discussed at a DR meeting and a selection procedure will be setup in order to arrive to a widely accepted decision.

November 17, 2009 LC e- cloud Working Group We have been asked: 1.To evaluate the proposal and options to reduce the DR circumference to 3.2 km comparing with the 6.4 km ring and give our recommendation on reducing the ring circumference to 3.2 km with respect to the electron cloud formation and instability. Timeline: early Working Group Charges

November 17, 2009 LC e- cloud Working Group Working Group Charges Then, 2.To evaluate electron cloud mitigation techniques, simulations and code benchmarking for the AD&I option. In particular, evaluate the differences between mitigations as grooves clearing electrodes, coating (TiN, TiZrV NEG and amorphous Carbon) regarding their feasibility, effectiveness, impact on the vacuum system, on the beam impedance and on costs, for different regions of the ILC DR as drifts, arc magnets and wigglers. Timeline late 2010.

November 17, 2009 LC e- cloud Working Group Goal of the R&D simulation effort is to quantify the Secondary Electron Yield (SEY) threshold for the onset of the electron cloud instability in the various DR configurations. As mitigations will be evaluated on their potential to offer a secondary electron yield lower than the SEY threshold Simulation Working group charges Timeline late 2010

November 17, 2009 LC e- cloud Working Group Deliverables Recommendation for the reduction of the ILC Positron Damping Ring Circumference Recommendation for the baseline and alternate solutions for the electron cloud mitigation in various regions of the ILC Positron Damping Ring. By March 2010 By Late 2010

November 17, 2009 LC e- cloud Working Group Report Document A clear document produced by the working group by (late) FY10 including the research work, a clear set of criteria for the recommendation and the recommendation itself.

November 17, 2009 LC e- cloud Working Group Report Document

November 17, 2009 LC e- cloud Working Group A large amount of work has been already produced and information available on mitigations such as on coatings, clearing electrodes and grooves from SLAC, KEK, CERN, CesrTA. In any case, it would be important to wait for the complete CesrTA input. The time scale for the working group to produce a recommendation should then be middle/end of 2010, or possibly coinciding with the completion of the R&D work on mitigations at CesrTA. Timeline and Time scale for the Recommendation

November 17, 2009 LC e- cloud Working Group CesrTA The working group will closely work with the CesrTA group to optimize the running schedule and define possible directions of both the experimental and simulation efforts. Important part of the working group effort will be the integration and scaling of the CesrTA results to the ILC DR.

November 17, 2009 LC e- cloud Working Group Presentation of the Work at ILC Damping Ring Meeting The working group will present a recommendation for mitigations to a Damping Ring meeting and a decision will be then made for the baseline as well as for alternate solutions. The mechanism for the decision remains yet to be defined. Within the damping ring group, a decision could be taken by means of a voting system based on scaling factors (example: mitigation costs, effectiveness, durability, maintenance etc.) to be defined.

November 17, 2009 LC e- cloud Working Group Reviewed at Albuquerque LCWA09 DR element% ringAntechamber need CoatingAdditional Mitigation Remarks DRIFT in STRAIGHT 33NoNEGSolenoidGrooves DRIFT in ARC 56Downstream of BEND only NEGSolenoidGrooves BEND7YesTiNGrooves WIGG3YesTiNElectrodes QUAD1Downstream BEND / WIGG TiNGrooves Preliminary table to be completed as input for Technical Design Phase. Goal is to turn all Red colors to Green as input for the recommendation. Other mitigations under development (carbon coating CERN/CesrTA)

November 17, 2009 LC e- cloud Working Group WebEx meetings Proposed frequency: –Bi-monthly Proposed day: –Tuesday Proposed time: –08:00 San Francisco time, 17:00 Rome time, 24:00 KEK time