Ion Issues Goal: define R&D plan producing a viable specification of machine settings within the next 2 (3?) years. Modeling / Simulations Experiments / Modeling-validation Remedies / Machine, beam parameters specifications

Talking points Modeling/Simulations Is the model/physics of FII well understood, adequate? e.g. photo-ions could be important, in particular in the wigglers where significant portion of radiation is emitted along the beam? …and the action item goes to … Oleg? Do the available codes capture all the relevant physics? Clarify issue on single-bunch vs. multi-bunch instabilities Strong-strong vs. weak-strong Feedback-modeling integrated in simulations? Survey of available simulations codes and simulators: Ohmi, KEK, (?) E-S Kim, (KNU), (?) Tor R, SLAC, (strong-strong) Lanfa Wang, SLAC, (weak-strong, strong-strong) Gouxing Xia, DESY (weak strong) Werner Bruns, CERN, (?) We should make an effort (short term action item) to document codes to ease communication test codes against each other (as well against measurements). E.g. investigate further convergence against numerics (how robust are results against choice of no. of kick stations?, etc)

Experiments / Validation of models The main value for experiments/measurements for us in validation of modeling/simulations Experimental demonstration that a ILC DR like beam can be made immune to FII, desirable but less likely An experiment with a non ILC-DR beam is useful only if it is accompanied by a robust simulation effort We should try to match measurement plans with simulators (e.g. proposal of simulations for ATF). There may be specific aspects that can be studied at certain facilities and not others (experiment proposals Facilities with programs to do FI experiments ATF  2007 only, 22 shifts * 8hrs available Proposal for experiments/simulations in place. Need to produce a detailed version Simulators involved: Lanfa, Guoxing (both at 50% FTE level) + in-house simulation capabilities Ohmi PLS No simulation program in place – not clear their commitment for further studies ALS Hopefully some measurements in 2007; plans to develop some in-house simulation capabilities; collaboration with L. Wang CESR(TA) >2008; can pick-up the torch from ATF; would make it possible to look at conditions closer to DR beam specifications.

Remedies/Machine settings Ion problem is coupled with, has implication for: vacuum, Depending on the choice of vacuum technology, vacuum composition may be different with possibly different implications for ions. Eg. In NEG coated chamber CO will be negligible, methane likely to be dominant feedback specifications Perhaps we can live with a feedback system that doesn’t have to kill the instability completely (Lanfa talk) design of bunch filling patterns, timing .... More invasive remedies: Clearing electrodes for “conventional” ions?