1. CesrTA EC Build-Up and Mitigation Program - Introduction Mark Palmer June 25, 2009

2. CTA092 EC Build-Up Studies Goals: –Instrument key regions in CESR to characterize EC around ring as input for characterizing beam-cloud interactions Drifts Dipoles Quadrupoles Wigglers –Validate EC Build-up simulations against detailed experiments –Develop instrumentation and techniques that can be used to study the efficacy of proposed EC mitigation techniques for the ILC DR

3. June 25, 2009CTA093 ILCDR Proposed Mitigation Table DR element% ringAntechamberCoatingAdditional Mitigation Remarks DRIFT in STRAIGHT 33NoNEGSolenoidGroove if necessary DRIFT in ARC 56Downstream of BEND only NEGSolenoidGroove if necessary BEND7YesTiNGrooves and Electrodes WIGG3YesTiNElectrodes and Grooves QUAD1Downstream BEND / WIGG TiNGrooves and Electrodes M. Pivi

4. June 25, 2009CTA094 EC Mitigation Studies Goals: –Short-term: Verify efficacy of proposed mitigation methods Principal focus is to validate mitigation techniques in wigglers and dipoles Perform testing of newly proposed mitigations wherever these fit within the program –Long-term: Where questions exist about the durability of proposed mitigations (particularly coatings), hope to support long- term testing parasitic with an ongoing CHES program Provide inputs to the ILCDR engineering design

5. June 25, 2009CTA095 Experimental Regions L3 EC experimental region PEP-II EC Hardware: Chicane, upgraded SEY station (coming on line in May) Drift and Quadrupole diagnostic chambers New EC experimental regions in arcs (wigglers  L0 straight) Locations for collaborator experimental chambers CHESS C-line & D-line Upgrades Windowless (all vacuum) x-ray line upgrade Dedicated optics box at start of each line Detectors share space in CHESS user hutches L0 region reconfigured as a wiggler straight CLEO detector sub-systems removed 6 wigglers moved from CESR arcs to zero dispersion straight Region instrumented with EC diagnostics and mitigation Wiggler chambers with retarding field analyzers and various EC mitigation methods (fabricated at LBNL in CU/SLAC/KEK/LBNL collaboration) CESR Ring

6. June 25, 2009CTA096 Tools Have developed thin RFA structures –~3mm thickness –Capable of fitting in standard dipole, wiggler, quadrupole chambers –Sacrifice some characteristics to ensure ability to characterize cloud in key regions Typically single grid structures Limited voltage range Some care required with efficiency curve Custom readout electronics and DAQ to allow simultaneous monitoring of full ring TE Wave measurements to cross-check

7. June 25, 2009CTA097 CESR Dipole Thin structure developed for use in limited aperture locations –CESR dipoles –CESR-c wigglers Application to standard CESR VC (dipole & drift)

8. June 25, 2009CTA098 Segmented RFA 2 grids, 5 collectors (probe azimuthal distribution of cloud) Simulation accurately predicts grid currents –Plot show absolute current! –Note that the retarding grid current goes negative in the data J. Calvey

9. June 25, 2009CTA099 Arc Regions 2 standard CESR VC RFAs deployed in dipole and drift regions in CESR –9 transverse collectors –3 transverse grids –Specifically Al chambers –Provide characterization of CESR arc cell Segmented RFAs –5 transverse collectors –2 grids (gnd + retarding in normal operation) –4 units deployed in CESR Arcs APS-Cornell comparison Cu vs TiN comparison Experimental chamber locations (Q15E/W)

10. June 25, 2009CTA0910 Wiggler RFAs Cu, TiN, Groove Electrode version in design Grooved Insert for CesrTA Wiggler @LBNL

11. June 25, 2009CTA0911 L0 Experimental Region Segmented RFAs Wiggler RFAs e+ Beam

12. June 25, 2009CTA0912 L0 Region Summary 2 (  3) Diagnostic wigglers –TiN and Cu VCs –3 rd wiggler with grooves to be installed next month –Each wiggler equipped with 3 RFAS 12 transverse collectors 1 grid Located at –Center of pole –Roll-off region –Pole boundary 3 Segmented RFAs in adjacent drifts –Each end of wiggler straight –Center of straight

13. June 25, 2009CTA0913 Application to CESR Large Bore Quadrupole Beampipe with 1740 transmission holes RFA grids with Hi-T meshes

14. June 25, 2009CTA0914 1740 0.75 mm dia holes Q48W Chamber

15. June 25, 2009CTA0915 Q48W VC with Retarding Grid

16. June 25, 2009CTA0916 L3 Experimental Region e+ e- WestEast Ion Detector (ERL) PEPII Chicane EC VC SEY Station Configured for In Situ SEY Measurements Sample Sample 1: Radial outside Sample 2: 45° from radial outside

17. June 25, 2009CTA0917 L3 Experimental Region Summary Presently have: –3 SLAC RFAs in chicane 17 transverse collectors 3 grids (2 gnd + retarding grid in middle) –4 th SLAC RFA to be installed with grooved test chamber next month –Quadrupole RFA 12 transverse collectors 1 retarding grid To be installed next month –SEY station – in testing –Room for additional experimental chambers