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Louis Rinolfi

Positron Source using Channelling for the CLIC baseline study. Louis Rinolfi. for the CLIC Sources collaboration. General CLIC layout for 3 TeV. Generation of e +. CLIC Main Beam Injector Complex. IP. e - Main Linac. e + Main Linac. e - BC2. e + BC2. 12 GHz. 12 GHz.

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Louis Rinolfi

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  1. Positron Source using Channelling for the CLIC baseline study Louis Rinolfi for the CLIC Sources collaboration

  2. General CLIC layout for 3 TeV Generation of e+

  3. CLIC Main Beam Injector Complex IP e- Main Linac e+ Main Linac e- BC2 e+ BC2 12 GHz 12 GHz 12 GHz, 100 MV/m, 21 km 9 GeV 48 km IP = Interaction Point SR= Spin Rotator BC = Bunch Compressor DR= Damping Ring PDR= Pre-Damping Ring AMD= Adiabatic Matching Device 3 TeV Base line configuration 2010 Booster Linac 6.14 GeV 2 GHz SR e+ BC1 2 GHz e- BC1 2 GHz 2.86 GeV 2.86 GeV e- DR e+ DR polarized e- unpolarized e+ e- PDR e+ PDR 2.86 GeV 2.86 GeV SR Injector Linac 2.66 GeV 2 GHz g/e+ Target e-/g Target Pre-injector e+ Linac 200 MeV Laser Pre-injector e- Linac 200 MeV Thermionic e- gun Primary e- Beam Linac 5 GeV DC gun Polarized e- Bunching system Bunching system AMD BC 2 GHz 2 GHz 2 GHz

  4. Yield and charge of e+ beam for 3 TeV Yield and charge along the Main Beam Injector Complex

  5. Four CLIC e+ studies 1) Baseline 3 TeV: (unpolarized e+) 7x109 e+/bunch (at injection of the Pre-Damping Ring) Pulse of 156 ns long with 312 bunches 2) Study for 500 GeV: (unpolarized e+) 14 x109 e+/bunch Pulse of 177 ns long with 354 bunches 3) Polarized positron for 3 TeV: See “The CLIC positron source based on Compton schemes” by L. Rinolfi et al., PAC09 See “Beam dynamics in Compton storage rings with laser cooling” by E. Bulyak et al., IPAC2010 See “An undulator based polarized positron source for CLIC” by W. Liu et al., IPAC2010 4) Study for 1 TeV < E < 3 TeV: See “CLIC energy scan” by D. Schulte et al., IPAC2010

  6. Flux of e+ x 42

  7. Comparison for PEDD PEDD = Peak Energy Deposition Density e+Amorphous target Thermionic e- gun Primary electron beam Linac 2GeV Amorphous W target (CLIC Note 465): Electron beam energy: 2 GeV Spot radius (rms): 1.6 mm Charge: 2x1012 e-/pulse Repetition frequency: 200 Hz Mesh volume = 0.425 mm3 Very good agreement for e- impinging an amorphous target

  8. Channeling of charged particles S. Dabagov U = potential (on axis) j = incidence angle

  9. Channeling process For W and for E > 1 GeV, channeling radiation becomes larger than bremsstrahlung Higher E, higher channeling effects crystal amorphous T. Suwada / KEK More soft photons with channeling

  10. SLAC test on crystal target in 1995-1996 A. Kulikov - L. R. 30 GeV e- beam Integrated e- flux: 2x1018 e-/mm2 Mosaic spread remains unchanged after irradiation: (0.4 mrad FWHM) Very encouraging result for crystal target X. Artru et al. “Radiation-damage study of a monocrystalline tungsten positron converter”, presented by R. Chehab at EPAC1998, CERN-PS-98-017-LP ; CLIC-Note-369 ; LAL-RT-98-02 Gamma diffractometry

  11. Primary Electron Beam Linac g/e+ Target e-/g Target Primary electron beam Linac Thermionic e- gun Bunching system 5 GeV Crystal Amorphous Electron beam parameters on the crystal target October 2009 With an yield of 1 e+/e- (at 200 MeV) , the charge is 7.5 x109 e-/bunch on the target. Parameters used for BINP/CERN/IPNL/LAL simulations

  12. Photon spectrum Crystal W target : Electron beam energy: 5 GeV Charge: 2.34 x1012 e-/pulse Spot radius: 2.5 mm (rms) V. Strakhovenko/BINP at crystal target exit Simulations with 6000 electrons Channeling: 20 photons / e-

  13. Photon evolution O. Dadoun /LAL From crystal target exit to amorphous target input

  14. Comparison for PEDD Strakhovenko code Mesh volume = 0.094 mm3 (ring shape) PEDD = 0.040 MeV / vol / e- PEDD = 0.427 GeV/cm3/e- PEDD = 15.5 J/g PEDD = Peak Energy Deposition Density 1 GeV/cm3 = 8.3x10-12 J/g for W Train of 312 bunches = 2.34x1012 e-s (e- spot) = 2.5 mm O. Dadoun GEANT4 results: Mesh volume = 0.25 mm3 (parallelepiped shape) PEDD = 0.285 MeV / vol / e- PEDD = 1.14 GeV/cm3/e- PEDD = 22.14 J/g Investigations are ongoing E. Eroglu, A. Ferrari FLUKA results: Mesh volume = 0.25 mm3 (parallelepiped shape) PEDD = 0.46 MeV / vol / e- PEDD = 1.83 GeV/cm3/e- PEDD = 35.5 J/g Not a good agreement for photons impinging an amorphous target

  15. Choice for CLIC targets GEANT 4 simulations CLIC Note 808 Power deposited in amorphous target Distance crystal - amorphous target e+/e- Thickness amorphous target Today choice

  16. Parameters for CLIC hybrid targets Dipole e- Primary electron beam Linac e- e- 5 GeV 3.1 1012 e-/train e+ g amorphous e+ crystal Crystal thickness: 1.4 mm Oriented along the <111> axis Distance (crystal-amorphous) d = 2 m Amorphous thickness e =10 mm

  17. Linac switching area at KEKB

  18. Setup at KEK Linac T. Takahashi / Hiroshima Uni. / KEK 8GeV e- Analyzing magnet 5 ~ 30MeV

  19. Preliminary results for e+ at 20 MeV conventional 8mm black: 1mm W crystal + 8mm W amorphous 3.4 enhancement Crystal aligned Crystal not aligned conventional 18mm e+ yield (ADC counts)

  20. Temperature rise by 1 bunch temperature measured with the thermo-couple attached at the back end of the amorphous target T[degree] rapid rise by bunch injection and and slow decrease by thermal diffusion in the target was clearly observed t [ms]

  21. Summary 1) The CLIC positron source for the 3 TeV is based on hybrid targets, using channeling but producing unpolarized e+. 2) Further studies are required regarding the simulations (with GEANT4, EGS4, FLUKA,…) of the Peak Energy Deposition Density which could be a big issue related to the target breakdown. 3) Experimental tests are mandatory. The KEKB results will be important step forward in the behavior of the targets.

  22. Acknowledgements Thank you for contributions and discussions: X. Artru, R. Chehab, S. Dabagov, O. Dadoun, E. Eroglu, A. Ferrari, T. Kamitani, T. Omori, E. Pilicer, F. Poirier, V. Strakhovenko, T. Suwada, T. Takahashi, A. Variola, A. Vivoli

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