Electron Cloud Studies for Tevatron and Main Injector Xiaolong Zhang AD/Tevatron, Fermilab

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron In Memory of A Great Physicist and an Excellent Mentor Francesco Ruggiero 1957–2007

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron In This Report … Electron Cloud Observations at Fermilab; The impact on Main Injector Upgrades and the research activities at Accelerator Division; Simulation methods, programs and results; Future study plans.

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Mechanism of Electron Cloud Buildup Short bunch:  Initial electron produced by photos, beam loss, ionization, etc.  Density of the electron increased by generating secondary electrons.  Exponential growth of electron density happens with appropriate beam conditions.  Electron cloud saturated by its space charge effect.

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Electrons Trapped in the Beam Long bunch or coasting beam  Initial electron generated  Electrons are trapped by beam potential  Trailing edge multipacting (long bunch case)

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Effects of Electron Cloud Vacuum instabilities:  Fast vacuum jumps of several order of magnitude Beam instabilities Beam losses Heat loading Noise on beam instruments

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Activities at Accelerator Division Initial observation of pressure rise at Tevatron with high intensity uncoalesced beam in Dec Initiated by Weiren Chou and Francois Ostiguy for Proton Driver Study in April More beam studies at Tevatron and some observations at Main Injector Obtained simulation codes POSINST, ECLOUD, PEI, etc. Collaborations with LBNL, CERN, APS, BNL, SLAC, etc. Got 2 RFA electron detector as gifts from APS, thanks for Kathy Harkay and Richard Rosenberg

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron SEY of S.S. Chamber Material SEY of new S/S chamber material for Fermi MI, after 1hr 150°C baking and cooling back to room temperature, prepared by W. Chou and measured by R. Kirby (SLAC)

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron RFA Testing Beam Pipe in Tevatron and MI RFA ION GAUGE ION PUMP

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Beam Studies at Tevatron (1) Bunch intensity threshold around 4e10/bunch for 30 bunches, vacuum section A0, D0, C0, E0, and F0

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Beam Studies at Tevatron (2) Beam lifetime 24.4hrs Emittance growth 34.8  /hr Tevatron 150GeV, 116e10/30bunches

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Beam Studies at Tevatron (3) Some beam Schottky power rise observed when the vacuum pressure rising

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Vacuum Squeeze, Sep. ON Ramp

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Beam Threshold of Vacuum Pressure Jump at Tevatron ~1.2E12/30 bunches

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Simulations for MI Upgrades Basic beam parameters Beam energy8.9 GeV Ring circumference m Maximum bunch intensity30e10/bunch Bunch number6 batch of 84 bunches Bunch spacing5.645 m Maximum bunch length0.75 m Gaussian Beam size rms5 mm round Residual gas pressure20 nTorr, room tempeture Beam pipe6.15 cm x 2.15 cm elliptical Electrons/proton loss1.27e-7 (e/p)/m

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Elliptical Beam Pipe Gröbner multipacting parameter Horz 1.28 Vert: Energy required for electrons to traverse beam chamber in one RF period Horz: 120 eV Vert: 19 eV Electron energy gain at the extremities of the ellipse (impulse aproximation) Horz: 2.3 eV Vert: 7.3 KeV Maximum beam kick (finite bunch length) 772 eV Larmor radius : KGs (From Report of Miguel Furman)

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Elliptical Beam Pipe With normal MI elliptical vacuum chamber and within bend magnets, at proton bunch intensity of 6e10, the electron cloud threshold for the bunch length of 0.54m, which means electron cloud happens during ramping and transition crossing where bunch length becomes shorter

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Elliptical Beam Pipe With Clearing Electrode Above electron cloud can be suppressed by the 500V clearing electrode in the beam pipe.

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron 6” Beam Pipe For the 6” beam pipe, the electron cloud happens even at bunch intensity of 10e10 proton/bunch at low SEY=1.3 The electron cloud can be suppressed by 50Gs solenoid or over 500V clearing electrode

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Electrons

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Electron

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Mitigations (1) Beam Scrubbing

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Mitigations (2) Bunched Beam Injection Pattern Solenoid

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Mitigations (3) Surface Coating with TiN or TiZrV (NEG) Surface Grooving 1 mm Measured SEY reduction < 0.8. More reduction depending geometry. Measured SEY reduction < 0.8. More reduction depending geometry. Special surface profile design, Cu OFHC. EDM wire cutting. Groove: 0.8mm depth, 0.35mm step, 0.05mm thickness.

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Mitigations (4) Clearing Electrode E Feedthrough E

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Mitigation Method (5) Alternate beam parameters, such as bunch length; intensities; etc. Change filling patterns, such as bunch spacing, satellite clearing bunches; etc.

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Simulations Small section of the beam pipe. Macro particles and discrete beam kick Space charge, electron and beam image charge included. Gaussian bunches (longitudinal bunch profile available for long bunches) Realistic secondary electron yield model. Electron longitudinal motion neglected Theoretical primary electron distributions

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Secondary Electron Yield CERN SLAC

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Future Plan Continue the detailed simulation for various beam and surface conditions Beam studies at Tevatron and MI:  Electron density vs. beam intensity.  Electron energy spectrum.  Bunch by bunch tunes, loss, emittances.  Vacuum changes. ● Comparing and benchmarking the simulation codes ● Test of mitigation methods with the test beam pipe: Solenoid, clearing electrodes, coating, grooving, etc. ● Does it exists in Booster?

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Summary Electron cloud effect is a limiting factor to the high energy, high intensity accelerator performance. It might have some impacts on magnet design. The simulations and initial observations show the electron cloud will be a problem for SNuMi and future Fermi neutrino programs. More studies and investments should be put into this researches.

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Backup slides

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron History of Electron Cloud Studies 1967 Novosibirk proton rings with coasting beam:  Two Stream Beam Instabilities;  Cure: various beam intensity and clearing electrode 1970 CERN ISR coasting beam  Cure: clearing electrode 1977 ISR bunched beam.  Vacuum pressure jumps End of 80s:  KEK PF Beam instabilities when switched from electron to positron  PSR Beam instabilities 1995 Two B-Factories: KEKB: Simulation code PEI; Beam studies KEK-BEPC; PEPII: Simulation code POSINST; LBNL-SLAC; TiN coating 1997 ECLOUD for LHC and SPS. CESR, APS, SNS, RHIC, etc. New simulation codes and methods keep appearing. Extensive SEY measurements; material and surface treatments.

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Electron Cloud for Various Accelerators MI

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Effects of the Electron Cloud Beam Instabilities KEKB BEPC PSR, 1988 Sideband Peak Height Betatron Oscillation Sidebands

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Effects of the Electron Cloud Beam Emittance Growth KEKB SPS

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Effects of the Electron Cloud Vacuum Pressure Bump dipole field no field RHICSPS

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Effects of the Electron Cloud Noise on BPM Pickup SPS

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Effects of the Electron Cloud Beam Loss SPS RHIC

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron Effects of the Electron Cloud Estimation of the Heat Load for LHC (Frank Zimmermann) high luminosity arc heat load vs. intensity, 25 ns spacing, ‘best’ model calculation for 1 train R=0.5  max =1.7  max =1.5  max =1.3  max =1.1  max = suffices BS cooling capacity injection low luminosity ECLOUD simulation

13-15 March 2007 IU ep-Miniworkshop, Xiaolong Zhang- FNAL, AD/Tevatron RFA ion signal