1. Nov 17, 2009 Webex Assessing the 3.2 km Ring feasibility: Simulation parameters for electron cloud Build-up and Instability estimation LC DR Electron Cloud Working Group Nov 17, 2009

2. November 17, 2009 LC e- cloud Working Group Simulation campaign We have been asked to give a recommendation of the feasibility of a 3.2 km DR with respect to electron cloud. Our recommendation has been requested for the re-baselining report SB2009 (March 2010) The work on the recommendation for mitigations and the related written report should follow the CesrTA program and be completed later in 2010

3. November 17, 2009 LC e- cloud Working Group Simulation campaign Next slides, will go through the parameter list needed for the electron cloud build-up and instability simulations. If a parameter is missing here or we feel we need a better value, please let’s have a discussion (now or offline) and a closer examination to the parameter

4. November 17, 2009 LC e- cloud Working Group Web link to 6.4 km DR files ILC Damping Rings Wiki at Cornell website: https://wiki.lepp.cornell.edu/ilc/bin/view/Public/Dampi ngRings/WebHomehttps://wiki.lepp.cornell.edu/ilc/bin/view/Public/Dampi ngRings/WebHome Consider Version: DCO4, 30 September 2009

5. November 17, 2009 LC e- cloud Working Group Web link to 3.2 km DR files For the MAD files need to ask Susanna and Marica. Post it on web?

6. November 17, 2009 LC e- cloud Working Group DR parameters Table 6.4 km3.2 km DR Version Name“DCO4” 90°“DSB3” Circumference (m)64763238 Energy (GeV)55 Bunch population2x10 10 Beam sizes  x-  y See next slides Emittance,  x (nm) 0.450.53 Emittance,  y (pm) 22 RMS Bunch length (mm)66 RMS Energy Spread1.27x10 -3 1.2x10 -3 Bunch spacing (ns)6.2 Momentum compaction1.62x10 -4 1.33x10 -4 RF frequency (MHz)650 Harmonic number140427021 Synchrotron tune0.0360.0166 Tunes Qx, Qy71.109, 71.39957.504, 32.954

7. November 17, 2009 LC e- cloud Working Group 6.4 km ring from M. Korostolev Maxim Korostelev at LCWA09

8. November 17, 2009 LC e- cloud Working Group Susanna Guiducci at LCWA09 3.2 km from S. Guiducci LCW09 talk

9. November 17, 2009 LC e- cloud Working Group

10. November 17, 2009 LC e- cloud Working Group Beam sizes 6.4km ring 3.2 km ring wiggler arc Arc + drift arc

11. November 17, 2009 LC e- cloud Working Group Ratio of beam sizes 6.4 km ring3.2 km ring

12. November 17, 2009 LC e- cloud Working Group Electron cloud build-up simulations: *let us define the cloud density that we are interested mostly as: density at equilibrium after electron cloud build-up density NEAR THE BEAM (10  x, 10  y) density JUST BEFORE electron cloud pinching (head of bunch) Build-Up Simulations 6.4 km DR 6.4km DRMagnetic Field Unit Length Aperture (from RDR) Antecha mber full height SEYBeam size  x,  y (um) Cloud density* BEND0.27 T2.0 mr=2510 mm0.9 ÷ 1.4260, 6deliverable QUAD12 T/m0.3 mr=2510 mm0.9 ÷ 1.4360, 6deliverable SEXT215 T/m 2 0.25 mr=2510 mm0.9 ÷ 1.4360, 6deliverable DRIFT (arc)- 1.0 mr=25none (but solenoid) 0.9 ÷ 1.4360, 6deliverable WIGG1.6 T2.45 mr=2310 mm0.9 ÷ 1.470, 5deliverable

13. November 17, 2009 LC e- cloud Working Group Electron cloud build-up simulations: *let us define the cloud density that we are interested mostly as: density at equilibrium after electron cloud build-up density NEAR THE BEAM (10  x, 10  y) density JUST BEFORE electron cloud pinching (head of bunch) Build-Up Simulations 3.2 km DR 3.2km DRMagnetic Field Unit Length Aperture (from RDR) Antecham ber full height SEYBeam size  x,  y (um) Cloud density* BEND0.36 T2.7 mr=2510 mm0.9 ÷ 1.4110, 5deliverable QUAD7.5 T/m0.3 mr=2510 mm0.9 ÷ 1.4270, 5deliverable SEXT145 T/m 2 0.25 mr=2510 mm0.9 ÷ 1.4350, 6deliverable DRIFT (arc)- 1.0 mr=25none (but solenoid) 0.9 ÷ 1.4270, 6deliverable WIGG**1.6 T2.45 mr=2310 mm0.9 ÷ 1.470, 5deliverable ** WIGG in 3.2 km ring similar to 6.4km ring

14. November 17, 2009 LC e- cloud Working Group Build-Up Simulations 3.2 km DR – 3 ns bunch spacing Option 3.2 km DRCloud density* BENDdeliverable QUADdeliverable SEXTdeliverable DRIFTdeliverable WIGGdeliverable In the 3.2 km DR only, we need to evaluate the cloud density the configuration option with shorter bunch spacing. In simulations, one should just change the bunch spacing from 6 ns to 3 ns, all the other parameters are kept the same.

15. November 17, 2009 LC e- cloud Working Group Instability Simulations Additional parameters 6.4 km3.2 km Ring“DCO4” – 90°“DSB3” Ring average  x (m) 18 m21.7 m Ring average  y (m) 19 m18.5 m Beam-cloud interactions: first use 40 kicks/turn for code benchmarking Beam-cloud interactions: then use a complete MAD or SAD lattice Use cloud density from build-up simulations Deliverable: define the instability threshold in 6.4 km and 3.2 km Rings

16. November 17, 2009 LC e- cloud Working Group Fill pattern For the 6.4 km ring fill pattern there is a table from Andy on the website: https://wiki.lepp.cornell.edu/ilc/pub/Public/Da mpingRings/WebHome/DampingRingsFillPatt erns.xls https://wiki.lepp.cornell.edu/ilc/pub/Public/Da mpingRings/WebHome/DampingRingsFillPatt erns.xls For the 3.2km ring we can assume just half of the bunch trains with the same number of bunches and the same train gaps.

17. November 17, 2009 LC e- cloud Working Group Photon parameters Average number of photons emitted per unit length per beam particle in the ARCS are: –0.33 photons/meter/e+ in the ARCS of 6.4 km ring –0.47 photons/meter/e+ in the ARCS of 3.2 km ring (Considering an average of 0.204 photons/meter/e+ around each ring and a fractional arc/circumference=4000m/6476m and 1400m/3238m) Photoelectric yield: 0.1 Need an improved estimation of the photon distribution in the ring (Cornell code)

18. November 17, 2009 LC e- cloud Working Group SEY simulation parameters REFERENCE for simulation SEY parameters: –Peak SEY: 0.9 ÷ 1.4 –Emax = 300 eV –Reflectivity: SEY(  0 eV) = 0.5 Comments / Suggestions !?

19. November 17, 2009 LC e- cloud Working Group Set of Criteria for Mitigations Mitigations should be selected according to the following criteria: 1.Costs and Maintenance 2.Allow maximum 10% emittance increase 3.SEY reduction potentials 4.Photo-emissivity 5.Impedance budget 6.Resistive wall?! 7.Durability 8.… Need to start discussing now, to give a weight to items in this list, prioritize and define a clear set of criteria for the mitigation selection

20. November 17, 2009 LC e- cloud Working Group Collaboration Work Needed now: assess the feasibility of the 3.2 km ring Photons calculation: Cornell Build-up simulations: Frascati, LBNL Single-bunch simulations: KEK, SLAC CERN Also, we can start looking at: Impedance calculation: KEK, Frascati (clearing electrodes) SLAC (grooves)

21. November 17, 2009 LC e- cloud Working Group or.. by Principal Investigators Needed now: assess the feasibility of the 3.2 km ring Photons calculation: Gerry Dugan Build-up simulations: Theo Demma, Miguel Furman, Marco Venturini Single-bunch simulations: Ohmi-san, Mauro Pivi Also, we can start looking at: Impedance calculation: Suetsugu-san and Shibata- san, David Alesini (clearing electrodes) Karl Bane (grooves)

22. November 17, 2009 LC e- cloud Working Group Collaboration Work The work on the recommendation for Mitigations can start LATER in FY10, with: Integration of CesrTA results Recommendation of electron cloud mitigations in the ILC DR Written Report for Recommendation

23. November 17, 2009 LC e- cloud Working Group Blackboard Please Susanna, could you send the 3.2km lattice with updated working point? Thank you! - Mauro Messages board By the way, could we post the 3.2 km lattice on the Cornell wiki site?