C ESR TA Status Report July 22, 2010 Mark Palmer for the C ESR TA Collaboration

Goal is to provide –Brief C ESR TA status report –Summarize upcoming plans Operations Analysis Incorporation of results into DR design –Start of run issues Overview July 22, 2010ILCDR Electron Cloud Working Group2

July 22, 2010ILCDR Electron Cloud Working Group3 C ESR TA R&D Goals –Studies of Electron Cloud Growth and Mitigation Study EC growth and methods to mitigate it (particularly wigglers and dipoles). Benchmark and expand existing simulation codes  validate projections to the ILC DR. –Low Emittance Operations EC beam dynamics studies at ultra low emittance (CesrTA vertical emittance target:  v <20 pm-rad). Beam instrumentation for ultra low emittance beams –x-Ray Beam Size Monitor targeting bunch-by-bunch (single pass) readout –Beam Position Monitor upgrade Develop LET tuning tools –Studies of EC Induced Instability Thresholds and Emittance Dilution Measure instability thresholds and emittance growth at ultra low emittance Validate EC simulations in the low emittance parameter regime. Confirm the projected impact of the EC on ILC DR performance. –Inputs for the ILC DR Technical Design Support an experimental program to provide key results on the 2010 timescale

C ESR TA Program Deliverables Validation of EC Build-Up Models –Significant data in hand RFA Coherent Tunes TE Wave Data Shielded pickup data –Excellent progress on simulations Coherent tune studies giving consistent results on SEY and PEY properties Local EC modeling and comparison with RFA data still has some way to go to provide SEY and PEY constraints –Inputs such as photon distributions –Full incorporation of RFA effects TE Wave Modeling (LBNL, Cornell work) Shielded pickup data  most critical issue is to obtain  (0) evaluation from witness bunch studies July 22, 2010ILCDR Electron Cloud Working Group4

Surface Characterization & Mitigation Tests DriftQuadDipoleWigglerVC Fab Al CU, SLAC Cu CU, KEK, LBNL, SLAC TiN on Al CU, SLAC TiN on Cu CU, KEK, LBNL, SLAC Amorphous C on Al CERN, CU NEG on SS CU Solenoid Windings CU Fins w/TiN on Al SLAC Triangular Grooves on Cu CU, KEK, LBNL, SLAC Triangular Grooves w/TiN on Al CU, SLAC Triangular Grooves w/TiN on Cu CU, KEK, LBNL, SLAC Clearing Electrode CU, KEK, LBNL, SLAC July 22, 2010ILCDR Electron Cloud Working Group5 = planned = chamber(s) deployed C ESR TA Phase I Mitigation Studies

Examples July 22, 2010ILCDR Electron Cloud Working Group6 V elec =0VV elec =400VWiggler Drift Quad Dipole

EC Mitigations EC Mitigation items –Full data analysis and preparation of PEY/SEY summary RFA/ analysis for specific mitigations In Situ SEY Station analysis (more samples) –NEG characterization –Post-scrubbing characterization after CHESS run which just finished Have taken initial data in July run (Tuesday & Wednesday evenings) – not yet analyzed… July 22, 2010ILCDR Electron Cloud Working Group7

Low Emittance Tuning Now operating at or near our 20pm-rad target –For single and multi-bunch studies –Further work to keep moving lower –Must maintain at least the present operating level Expect to have an almost daily effort during present run Will require reliable BPM and xBSM operation In a good position to pursue things like IBS studies July 22, 2010ILCDR Electron Cloud Working Group8

Emittance Dilution Characterization of instability thresholds and emittance-diluting effects as a function of emittance is the remaining deliverable of the CesrTA program –Preliminary results obtained during the previous run look very promising! –July run is to be focused on making the first round of systematic studies in the ultra low emittance regime. July 22, 2010ILCDR Electron Cloud Working Group9

Beam Instabilities & Emittance Growth July 22, 2010ILCDR Electron Cloud Working Group10 50 dB Head-Tail F v +F s FvFv 263 KHz * Bunch #1Bunch #25Bunch #40 40 kHz Bunch-by-bunch measurements - xBSM Single-bunch (head-tail) – spectral methods and growth rates Multi-bunch modes via feedback and BPM system Modeling: KEK-Postech (analytical estimates and simulation) SLAC-Cornell (CMAD) Frascati (multi-bunch instability) Current scan in 45 bunch positron train  Look for onset of head-tail instability 2 GeV Low Emittance Lattice, 14ns bunch spacing –F v & Head-Tail Mode spectra (expected at F v + F s ) –Synchrotron Tune ~26 kHz 1.3 mA/bunch 2.1×10 10 e+/bunch

Beam Size Measure Bunch-by-Bunch Beam Size Same current scan as on preceding page –Beam size enhanced at head and tail of train Source of blow-up at head requires further investigation (resonance? other?). Bunch lifetimes (Touschek-limited) qualitatively consistent with relative bunch sizes. –Beam size measured around bunch 5 is consistent with  y ~ 20pm-rad (  y =11.0  0.2  m,  source =5.8m) July 22, 2010ILCDR Electron Cloud Working Group11 0.8×10 10 e+/bunch, Each point: Average of 4096 single-turn fits 1.6×10 10 e+/bunch Single Turn Fit Bunch 5 Consistent with onset of instability Consistent with 20 pm-rad

Simulation of Incoherent  y  Growth & Instabilities CMAD simulation (Pivi, Sonnad) CMAD: tracking and e-cloud beam instability parallel code (M.Pivi SLAC) –Distribute EC in every magnetic element of ring: ~1,000 elements including drift, dipoles, quad, sext, etc. –Apply beam-cloud IP in every element July 22, 2010ILCDR Electron Cloud Working Group12 DC04 lattice: 6.4 km ring 2.5e11 2.2e11 2.0e11 1.7e11 Beam losses Application to ILC DR 1e12 5e11 1e11 5e10 1e10 no cloud C ESR TA C ESR TA Tune Footprint Lattice: cta_2085mev_

Schedule July 22, 2010ILCDR Electron Cloud Working Group13 Taken from ILC DR Planning GANTT Chart Baseline EC WG Recommendation Run Just Beginning

Current Run –July 20 th – morning of August 3 rd –Major focus on Low Emittance Operations (  mainly 2 GeV) Experiments at Low Emittance –EC Instability Characterizations –Emittance Growth Studies –IBS Characterization of Processed Vacuum Chambers and other EC Build-Up Studies –Shielded Pickup Studies Startup –1 major problem – RF HV PS Failure –Secondary failure on spare HV PS –Repairs underway today – no guarantees but we are hopeful –May extend the run to middle of the week of August 2 to make up lost time. Current Run July 22, 2010ILCDR Electron Cloud Working Group14

Reporting Milestones ECLOUD 10 – October 8-12 (Friday-Tuesday) –Satellite meeting for ILC DR EC Evaluation on Wednesday, October 13 –Registration Open EC Working Group Recommendation/Report International Workshop on Linear Colliders 2010 CERN – October July 22, 2010ILCDR Electron Cloud Working Group15