c esr ta status report july 22, 2010 mark palmer for the c esr ta collaboration
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CESRTA Status ReportJuly 22, 2010
Mark Palmerfor the CESRTA Collaboration
• Goal is to provide– Brief CESRTA status report– Summarize upcoming plans
• Operations• Analysis• Incorporation of results into DR design
– Start of run issues
Overview
July 22, 2010 ILCDR Electron Cloud Working Group 2
July 22, 2010 ILCDR Electron Cloud Working Group 3
CESRTA 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 a validate projections to the ILC DR.
– Low Emittance Operations• EC beam dynamics studies at ultra low emittance
(CesrTA vertical emittance target: ev<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
CESRTA 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 a most critical issue is to obtain d(0) evaluation
from witness bunch studies
July 22, 2010 ILCDR Electron Cloud Working Group 4
Surface Characterization & Mitigation Tests
Drift Quad Dipole Wiggler VC FabAl 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, 2010 ILCDR Electron Cloud Working Group 5
= planned = chamber(s) deployed
CESRTA Phase I Mitigation Studies
Examples
July 22, 2010 ILCDR Electron Cloud Working Group 6
Velec=0V Velec=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, 2010 ILCDR Electron Cloud Working Group 7
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, 2010 ILCDR Electron Cloud Working Group 8
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, 2010 ILCDR Electron Cloud Working Group 9
Beam Instabilities & Emittance Growth
July 22, 2010 ILCDR Electron Cloud Working Group 10
50 dB
Head-Tail Mode @ Fv+Fs
Fv
263 KHz
*
Bunch #1 Bunch #25 Bunch #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 a Look for onset of head-tail instability• 2 GeV Low Emittance Lattice, 14ns bunch spacing
– Fv & Head-Tail Mode spectra (expected at Fv + Fs)– Synchrotron Tune ~26 kHz
1.3 mA/bunch2.1×1010e+/bunch
Preliminary
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 ey ~ 20pm-rad (sy=11.00.2 mm, bsource=5.8m)
July 22, 2010 ILCDR Electron Cloud Working Group 11
0.8×1010 e+/bunch,Each point: Average of 4096 single-turn fits
1.6×1010 e+/bunchSingle Turn FitBunch 5
Consistentwith onsetof instability
Consistentwith
20 pm-rad
Preliminary
Simulation of Incoherent ey 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, 2010 ILCDR Electron Cloud Working Group 12
DC04 lattice: 6.4 km ring
2.5e11
2.2e11
2.0e11
1.7e11
Beam losses
Application to ILC DR
1e125e111e115e101e10no
cloud
CESRTA
CESRTA Tune Footprint
Lattice:cta_2085mev_20090516
Schedule
July 22, 2010 ILCDR Electron Cloud Working Group 13
Taken from ILC DR Planning GANTT ChartBaseline EC WGRecommendation
Run JustBeginning
• Current Run– July 20th – morning of August 3rd
– Major focus on • Low Emittance Operations (a 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, 2010 ILCDR Electron Cloud Working Group 14
ILCDR Electron Cloud Working Group 15
Reporting Milestones
• ECLOUD 10 – October 8-12 (Friday-Tuesday)– Satellite meeting for ILC DR EC Evaluation on
Wednesday, October 13– Registration Openhttp://www.lepp.cornell.edu/Events/ECLOUD10/WebHome.html
• EC Working Group Recommendation/ReportInternational Workshop on Linear Colliders 2010
CERN – October 18-22
July 22, 2010
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