Goals of the Workshop Miguel Furman LBNL 31st ICFA Advanced Beam Dynamics Worksop ECLOUD04

1. Lawrence Berkeley National Laboratory Goals of the Workshop Miguel Furman LBNL 31st ICFA Advanced Beam Dynamics Worksop ECLOUD04 Napa, California, April 19-23, 2004

2. Lawrence Berkeley National Laboratory ECLOUD04 Goals • Long-bunches • spallation neutron sources: PSR, SNS, ISIS, ... • intense proton sources for HEP (JPARC, … • heavy-ion fusion drivers • LHC superbunches • Understand qualitative differences with short-bunch machines • How to suppress the effect • would solenoids work as well as they do for PEP-II and KEKB? • are clearing electrodes practical?

3. Lawrence Berkeley National Laboratory ECLOUD04 Goals • Lepton rings (PEP-II, KEKB, BEPC,…) • have learned how to suppress electrons via solenoids • machines working far beyond nominal specs, but only after electrons were suppressed. • PEP-II had arc chamber coated with TiN, but wasn’t enough; why? • understand single-bunch instability differences in PEP-II vs. KEKB (V or H?)

4. Lawrence Berkeley National Laboratory ECLOUD04 Goals • Simulations • progress towards 3D simulations • progress towards self-consistent (bunch-cloud both dynamical) simulations • in what cases is the 3rd dimension important? (basics physics, not so much simulation issue) • not for short-bunches, somewhat for spallation sources, important for HIF drivers; why? • List of code features, contact persons, availability, etc • Code benchmarks

5. Lawrence Berkeley National Laboratory ECLOUD04 Goals • Surface material properties and gas sources • SEY • gas desorption • electron generation from stray beam particles • ionization of residual gas • How well do we know them (eg., SEY below ~10 eV) • do we have reliable, standardized, reproducible measurements? • are new, more precise, measurement apparatuses called for? • How fast and how does the surface improve due to conditioning? • When does the primary electron source dominate over secondary electron source?

6. Lawrence Berkeley National Laboratory ECLOUD04 Goals • Suppression techniques • TiN and TiZrV coatings are “good”; • how good? • how bad a drawback is the required activation of TiZrV. eg., in the LHC straights? • TiN coating samples at PSR show mixed results (though generally favorable) • SNS chamber has been coated • what to do if SNS shows a higher-than-expected ECE? • what to do if LHC shows a higher-than-expected ECE? • PEP-II arcs were initally TiN coated (Al chamber) • why were solenoids required in the PEP-II arcs in addition to the straight sections? • how big an improvement can be attributed to the arc solenoids? • what would the performance have been without TiN coatings? • What to do when solenoids are not practical?

7. Lawrence Berkeley National Laboratory ECLOUD04 Goals • Do we know enough from experience and simulations to construct a “parameter phase space” for the ECE? • we are doing more and more detailed simulations, but we also should be distilling what we learn from them a global knowledge • step back from detailed accuracy in favor of an approximate picture • identify a few important parameters • e.g, temperature, applied magnetic field, magnetization in a ferromagnet • ECE: for example: electron line density vs. bunch spacing, bunch intensity, and effective SEY • Is this possible in general? • probably not, but should be possible within a given context

8. Lawrence Berkeley National Laboratory ECLOUD04 Goals • Foster collaborations • simulations, theory, experiments • Understand differences in calculations, measurements • iron them out, or decide which are more reliable than others

9. Lawrence Berkeley National Laboratory ECLOUD04 Goals • I am sure there are other important questions • I do not expect clear answers to all of them • but at least keep them in mind in our future work