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.

Estimation of antechamber protection in ILC-DR In order to calculate the number of photons that remain inside the chamber, we must integrate the fundamental spectrum of synchrotron radiation The calculation is done by numerical integration taking into account the geometry of the chamber and the curvature of the orbit (extrapolated by mad lattice files: Very preliminary estimate for ILC-DR DCO4 lattice indicate that only ~2% of the radiated photons remain inside the chamber (to be double checked)

4 Build Up Input Parameters for ECLOUD Bunch population NbNb 2.1x10 10 Number of bunches NbNb 45 x 4 trains Bunch gap Ngap 15 Bunch spacing L sep [m] 1.8 Bunch length σ z [mm] 6 Bunch horizontal size σ x [mm] 0.26 Bunch vertical size σ y [mm] Photoelectron Yield Y 0.1 Photon rate (e - /e + /m) dn  /ds Antechamber protection  90%; 97% Photon Reflectivity R 20%; 50% Max. Secondary Emission Yeld δ max 1.2 Energy at Max. SEY Ε m [eV] 300 SEY model Cimino-Collins (  (0)=0.5) ilc-DR 6.4 Km, 6 ns bunch spacing*. *