1 Impedance-related and others collective effects Impedance-driven collective effects/Instabilities –Single-Bunch (very high priority) –Multiple-bunch (high priority) Other Collective effects –CSR (moderate priority) –Space charge (moderate priority) –IBS (moderate priority) –Tousheck lifetime (moderate priority) [Ion effects (very high priority)] In these telemeetings we’ll keep focus on very high or high priority items (without forgetting the others)

2 Impedance Issues: milestones outlined at ILCDR06: 1.Produce initial technical designs for: (a) vacuum system (~ 2 years for ~ 2 FTEs), and (b) RF cavities (> 2 years). 2.Produce preliminary impedance model based on general specifications and scaling from existing machines/designs. (~ 1 year time frame for 1 FTE). 3.Make preliminary estimates of thresholds, growth rates, HOM heating etc. based on preliminary impedance model. (~ 1 year time frame) 4.Construct detailed impedance model based on initial technical designs for vacuum system and RF cavities (as information from milestone 1 becomes available; ~ 1 year) 4½. Specify feedback system model. 5.Characterize the impedance-related collective effects. (follows 4; ~ months) 6.Specify revised design parameters, and produce optimized technical designs (low risk and cost) for vacuum system and RF cavities. (following TDR) 7.Produce revised impedance model and updated characterization of impedance-related collective effects. (following TDR) 8.Prototyping and testing (in parallel with 6 and 7). Slide by A. Wolski (ILCDR06 Summary Talk) Slide by A. Wolski (ILCDR06 Summary Talk)

3 Matching R&D objectives and proposed activities Task Force S3 will soon start to work on –Identifying possible gaps and overlaps of efforts –Harmonizing activity proposals –Prepare detailed DR Global R&D Plan Harmonization will involve direct communications with various groups that have proposed activities These telemeetings should provide ground for discussion of Task Force S3 proposals, and provide feedback We should give some thought to how we will structure the coordination of people from different institutions working on the same or related topics. One of the challenges is to keep the flow of communication going. This is critical because of the natural inter-dependency between many activities (e.g. machine components design and optimization, impedance modeling, estimates of instabilities …)

4 The Baseline Configuration Study Report (Feb. 06) identified the microwave instability as the potentially most critical impedance-driven instability (hence the very high priority mark) Assessment based on –very rough estimate of the total impedance –very rough determination of current threshold for instability (based on some variant of the Boussard criterion) What we need (and eventually want to do) is clear: –Come up with a reasonably accurate model of the impedance (or wake potentials) based on E&M Mafia-style calculations of critical machine components (for some components an analytical-formula based description may be adequate) –Simulate the dynamics using the above accurate impedance model Some ideas on how to go about modeling longitudinal single-bunch instabilities

5 Setting a path toward goal 1.Identify all sources of potentially harmful impedance. Identify people responsible for design, modeling of machine components 2.Construct impedance (wake potential) models for specific components based on analytical formulas and impedance calculations carried out for existing machines. 3.Progressively replace models of specific components with more accurate numerical models as they become available. –Numerical models initially based on designs scaled from other machines will eventually reflect the technical design for the ILC DR’s components 4.Keep updating the estimates of the instability threshold, learn about sensitivity to impedance model, feedback information to machine component-designers Creating a space on the ILC-DR wiki site to keep all available info up to date would be very useful

6 1. Identify impedance sources … Maintain a database with updated info for relevant components including: currently best available impedance model; names of contact people for conceptual, technical design, and impedance calculation Filling this table should be one of first tasks. Filling this table should be one of first tasks. “Rank” specifies a tentative assessment of impact on dynamics (to be used as a guideline to set priorities in our studies) “Rank” specifies a tentative assessment of impact on dynamics (to be used as a guideline to set priorities in our studies)