AEC09, CERN Mauro Pivi, SLAC TiN chambers and SEY measurements in PEP-II M. Pivi J. Ng, T. Markiewicz, D. Kharakh, R. Kirby, F. Cooper, C. Spencer, B. Kuekan, J. Seeman, L. Wang, U. Wienands, A. Kulikov, T. Raubenheimer (SLAC) AEC09 CERN October 2009

AEC09, CERN Mauro Pivi, SLAC Outline of the talk Overview of PEP-II TiN coated chamber ILC tests: Secondary Electron Yield measurements of samples installed in PEP-II (“ECLOUD1”) Electron cloud tests in magnets in a dedicated Chicane built in PEP-II (“ECLOUD3”)

U. Wienands, ICFA WS BNL TiN coating on the arc chambers only Straight chambers in stainless steel and NO coating Overview of PEP-II TiN/Al Stainless steel

U. Wienands, ICFA WS BNL 9-Nov-03 Low Energy Ring LER Positron Arc Vacuum System Al extrusion, TiN coated, with antechamber for synchrotron radiation, discrete photon stops with localized Ti sublimation pumps baked & gdc before installation Beam pipe aperture 9x5cm Antechamber Courtesy

U. Wienands, ICFA WS BNL 9-Nov-03 Pressure vs Beam Current Nonlinear pressure rise with beam current has been seen in the LER early on. –No such effect seen in the HER It is accompanied by a growth in beam size –in both planes –Horizontal growth seems specific to PEP, not seen in other e + machines. It is reduced with solenoidal magnetic fields. –Part of the pump current is due to electrons

U. Wienands, ICFA WS BNL 9-Nov-03 Current, mA Feb A Feb A Oct AOct A Electron multipacting in the LER non-coated straight sections. Current, mA Feb A Upstream straightDownstream straight

U. Wienands, ICFA WS BNL 9-Nov-03 VP _29_03VP4031 (6-8)-Jul-01 Solenoid OFF VP Aug-01 Solenoid ON 14-Aug-01 Elec Electrons in the LER arcs TiN coated

U. Wienands, ICFA WS BNL 9-Nov-03 Bunch-by-Bunch Luminosity F.-J. Decker et al., ca ≈0.9 µs (100 bunches) decay time I b ≈ 1.2 A 8.4 ns (by-4) no solenoids

AEC09, CERN Mauro Pivi, SLAC TiN coating in PEP-II Summary PEP-II reached 3 x Design Peak Luminosity. Presumably TiN coating and antechamber in arcs played a big role (!) Un-coated straight sections much more going on: pressure bumps. It might have significantly helped to coat the straight sections too No direct data about TiN coated vs un-coated, since no electron detectors were installed at the time yet, i.e –Note also larger chamber aperture in straight sections PEP-II colleagues: J. Seeman, A. Kulikov, U. Wienands, D. Wright (SLAC), M. Zisman (LBNL) et al.

AEC09, CERN Mauro Pivi, SLAC Durability and aging of TiN coated PEP-II chambers Just removed chamber from PEP-II LER, Sep 2009 Cutting samples and analyzing TIN surface after 10 years operation at ~2-2.5A

AEC09, CERN Mauro Pivi, SLAC SEY measurements in PEP-II: “ECLOUD1” Later in 2007, ILC tests: Installed samples in-situ in a dedicated chamber (“ECLOUD1”) in PEP-II Samples could be inserted and removed in high vacuum and transported at SLAC laboratory system set-up for SEY measurements and surface analysis Replaced samples in PEP-II every ~ 6 weeks average; at PEP-II stops

AEC09, CERN Mauro Pivi, SLAC “ECLOUD1” SEY test station in PEP-II Transfer system at 0 o PEP-II LER e+  Transfer system at 45 o 2 samples facing beam pipe are irradiated by SR Isolation valves ILC tests, M. Pivi et al. – SLAC

AEC09, CERN Mauro Pivi, SLAC

AEC09, CERN Mauro Pivi, SLAC sample surface exposed to SR PEP-II LER side Surface analysis Tests Expose samples to PEP-II LER synchrotron radiation and electron conditioning. Then, measure Secondary Electron Yield (SEY) in laboratory. Samples transferred under vacuum. 20 mm ILC tests, M. Pivi et al. – SLAC

AEC09, CERN Mauro Pivi, SLAC M. Pivi et al. – SLAC

AEC09, CERN Mauro Pivi, SLAC Sample Transferring into SLAC Surface Analysis System

AEC09, CERN Mauro Pivi, SLAC Preview of results PEP-II beam conditioning highlights: TiN best performances, measured SEY < 1, –Carbon and Oxygen content decreased –Kept in stand-by in vacuum: SEY<1 even after 1000 hours (!) TiZrV non-evaporable getter (NEG), SEY  1 Stainless steel conditions but it recontaminates to high SEY after days of standing-by in vacuum Aluminum conditioned but still SEY > 2!

AEC09, CERN Mauro Pivi, SLAC TiN conditioning in PEP-II TiN samples measured before and after 2-months conditioning in the beam line. Samples inserted respectively in the plane of the synchrotron radiation fan (0 o position) and out (45 o ). ILC tests, M. Pivi et al. – SLAC Before installation in beam line After conditioning e- dose > 40mC/mm**2

AEC09, CERN Mauro Pivi, SLAC LER#1 XPS Before installationXPS After exposure in PEP-II LER for 2 months (e dose 40mC/mm^2) Carbon (and Oxygen) contents are strongly reduced after exposition to PEP-II synchrotron radiation, ions and electron cloud environment. Note: historically, bombardment with electron beams in surface analysis system set-ups shows carbon content rather increases … ! Surface analysis, decrease of Carbon content X-ray Photon Spectroscopy. ILC tests, M. Pivi et al. – SLAC

AEC09, CERN Mauro Pivi, SLAC Aluminum conditioning in PEP-II After long conditioning in PEP-II beam line: sample SEY maximum remains > 2 Well supported by previous SLAC and CERN laboratory system measurements CesrTA / Daphne have aluminum vacuum chambers: expect large e-cloud effects M. Pivi, R. Kirby – SLAC

AEC09, CERN Mauro Pivi, SLAC NEG conditioning in PEP-II ILC tests – SLAC NEG as received After beam conditioning March 2008 After NEG heating Caution about activation: during NEG transferring for measurements, we can’t ensure the vacuum to be CO, CO2 source free. NEG heating 200deg for > 2 hours

AEC09, CERN Mauro Pivi, SLAC Recontamination effects Measured SEY after keeping the samples in stand-by in high vacuum 1e-9 Torr and H2:CO ratio 10:1, typical of accelerator beam lines.

AEC09, CERN Mauro Pivi, SLAC TiN surface standing-by in vacuum: SEY < 1 after 1000 hours. Recontamination effects are small for TiN after conditioning in PEP-II. Surface recontamination after long term exposure in vacuum environment: TiN

AEC09, CERN Mauro Pivi, SLAC Surface Recontamination: Stainless Steel

AEC09, CERN Mauro Pivi, SLAC SEY before installation SEY after conditioning TiN/Al TiZrV Cu StSt* Al Summary “ECLOUD1” experiment Summary of samples conditioned in the accelerator beam line References: – paper in preparation for submission to Physical Review ST AB and Phys. Rev. Lett. – M. Pivi et al. MOPP064 EPAC 2008; – F. Le Pimpec et al. Nucl. Inst. and Meth., A564 (2006) 44; – F. Le Pimpec et al. Nucl. Inst. and Meth., A551 (2005) 187; *Stst showed larger re-increase of SEY to ~1.6 if left standby in vacuum

AEC09, CERN Mauro Pivi, SLAC Electron cloud tests in PEP-II Chicane In 2008: Installed a dedicated chicane (“ECLOUD3”) in PEP-II Vacuum chamber with 2 sections: un-coated Aluminum and TiN-coated Groove chamber TiN coated: manufactured, not installed and later sent to CesrTA. –ongoing tests in CesrTA (see M. Palmer presentation)

AEC09, CERN Mauro Pivi, SLAC “ECLOUD3”: Layout of PEP-II Chicane LER HER PEP-II ILC CHICANE

AEC09, CERN Mauro Pivi, SLAC “ECLOUD3” Chicane: Vacuum Chamber Layout 2 chambers: 135.3” and 31.2”. 4 analyzer electron cloud detectors, one at each magnet location The Al chamber is partially coated with TiN Aluminum TiN coating on Al [Groove]

AEC09, CERN Mauro Pivi, SLAC ILC tests, M. Pivi et al. – SLAC

AEC09, CERN Mauro Pivi, SLAC Electron detectors BEND iron plates e+e+ TiN and Al test chamber

AEC09, CERN Mauro Pivi, SLAC

AEC09, CERN Mauro Pivi, SLAC Electron cloud detectors in dipole, SLAC Electron detectors, Retarding Field Analyzer (RFA) type [R. Rosenberg, K. Harkay] M. Pivi and R. Kirby design, SLAC 17 collectors to measure horizontal e- distribution and 3 grids to measure e- energy spectrum Beam direction

AEC09, CERN Mauro Pivi, SLAC Preview of chicane results Measured > 3 order of magnitude lower electron cloud current in TiN section with respect Aluminum, in dipole field at 2.5A beam current. Observed new Resonance Effect previously predicted by simulations (C. Celata), electron cloud currents modulation as a function of dipole field.

AEC09, CERN Mauro Pivi, SLAC Chicane OFF: Electron cloud in field-free TiN coated section (signal below; 17 collectors) measured a factor ~20-30 lower than bare Aluminum section (above).

AEC09, CERN Mauro Pivi, SLAC Chicane ON: electron cloud in dipole field Un-coated Aluminum sectionTiN-coated section TiN section order of magnitude lower cloud current than Al. Classical “two-stripe” e- distribution in the horizontal plane. Horizontal plane L. Wang et al.

AEC09, CERN Mauro Pivi, SLAC ECLOUD3: Magnetic field Resonances Experimentally observed a modulation of the electron cloud current with the chicane magnetic field “n” is linearly proportional to the magnetic field Cyclotron phase of electrons with respect to the bunch spacing, affects the electron energy gain, leading to the observed modulation Resonance peaks are separated by integer values of n M. Pivi, J. Ng et al, SLAC

AEC09, CERN Mauro Pivi, SLAC ECLOUD3: Summary Goal: mitigation of electron clouds in a dipole magnetic field region Results: –Demonstrated TiN-coating is very effective in a dipole –Characterized electron cloud in DR dipole field –Observed new resonance: modulation in electron flux as magnetic field strength is varied –Resonance: reduce electron cloud density in ILC Damping Ring by tuning the dipole field in the arc References: –paper being prepared for submission to Nucl. Instr. Meth. –M. Pivi, J. Ng et al., EPAC 2008;

AEC09, CERN Mauro Pivi, SLAC CesrTA and Project-X SLAC electron cloud test chamber studies continues, Thanks to Cornell and Fermilab. –Redeployed all the electron cloud experiments from PEP-II to CesrTA Some of the tests are going to be re-deployed further to Fermilab for Project-X

AEC09, CERN Mauro Pivi, SLAC TiN coating & facilities at SLAC SLAC Klystron Department: TiN samples SLAC Vacuum Group, TiN coating: PEP-II LER arcs chambers, 1998 PEP-II test chambers CESRTA / PEP-II chicane 2008 CESRTA: Wiggler and Groove vacuum chambers, 2009 KEKB: Groove tests in Wiggler, 2009

AEC09, CERN Mauro Pivi, SLAC Summary Presumably TiN coating and antechamber in arcs played an important role in the achieving of high Luminosity in PEP-II ILC tests: Conditioning in situ PEP-II: TiN best performances –Carbon and Oxygen content decreased –Kept in stand-by in vacuum: SEY<1 even after 1000 hours (!) Conditioning in situ PEP-II: Good also NEGs and Copper. Stainless steel recontaminates to higher values SEY~1.6 Demonstrated TiN-coating is very effective in a dipole: order of magnitude lower cloud current than in aluminum section Tests continue at CesrTA and Fermilab