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