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Electron Cloud in ilcDR: Update

Explore Electron Cloud Buildup in ILC-DR and parameters for simulation. Understand effects of photon reflectivity and antechamber protection. Determine photon absorption fraction in antechambers.

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Electron Cloud in ilcDR: Update

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  1. Electron Cloud in ilcDR: Update T. Demma, INFN-LNF

  2. Electron cloud buildup simulation • Cloud buildup was calculated by code “ECLOUD” developed at CERN. • Assumptions: - Round Chambers - A fraction R of the primary electrons are uniformly produced on chamber wall. - A reduced number of primary electrons is artificially used in order to take into account the reduction of electron yield by the ante-chamber: where: dn/ds is the average number of emitted photons per meter per e+, Y is the quantum efficiency, and  is the percentage of photons absorbed by the antechambers.

  3. Build Up Input Parameters for ECLOUD ilc-DR 6.4 Km, 6 ns bunch spacing*. *https://wiki.lepp.cornell.edu/ilc/pub/Public/DampingRings/WebHome/DampingRingsFillPatterns.xls

  4. Buildup in ilc-DR arcs: Dipoles Snapshot of the electron (x,y) distribution “just before” the passage of the last bunch By=0.27 T; R=20% =90%=97% Average e-cloud density Center density “just before” bunch passage

  5. Buildup in ilc-DR arcs: Dipoles Snapshot of the electron (x,y) distribution “just before” the passage of the last bunch By=0.27 T; R=50% =90%=97% Average e-cloud density Center density “just before” bunch passage

  6. Summary • Preliminary simulations indicate that for a peak secondary electron yield of 1.2 there is a strong dependence of the electron cloud build-up by photo-emission parameters such as photon reflectivity and antechamber protection. • Are there “reliable” values for these parameters? • Or should we scan a range of values? • An estimate of the fraction of photon absorbed by the antechambers can be obtained following: M.A.Furman and G.R.Lambertson, LBNL-41123. I have already used this technique for DAFNE, but I need time…..

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