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Impact of synchrotron radiation in LEPTON COLLIDER arcs

Impact of synchrotron radiation in LEPTON COLLIDER arcs. Francesco Cerutti , Alfredo Ferrari, Luisella Lari *, Alessio Mereghetti. *BE department. Acknowledgments: B. Holzer , R. Kersevan , A. Milanese. FCC study kickoff meeting Lepton collider design

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Impact of synchrotron radiation in LEPTON COLLIDER arcs

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  1. Impact of synchrotron radiation in LEPTON COLLIDER arcs Francesco Cerutti, Alfredo Ferrari, LuisellaLari*, AlessioMereghetti *BE department Acknowledgments: B. Holzer, R. Kersevan, A. Milanese FCC study kickoff meeting Lepton collider design University of Geneva, Feb 14, 2014

  2. OUTLINE • simulation of synchrotron radiation interaction • a (too?) much preliminary layout and the role of absorbers • power sharing • beam chamber and water heating • dose to hypothetical coils • ozone production • a shielded beam chamber • absorption and leakage • photoneutrons and activation

  3. SYNCHROTRON RADIATION

  4. SYNCHROTRON RADIATION E>100 eV 99.99964% of the total power 95.75% of the photon amount <E>=395keV • E= 8.5 GeV/turn (dE/ds=1.375 keV/cm in the dipoles) • P = 8.5 x I[mA] MW = 8.5 x 10mA = 85 MW in the whole accelerator (dP/ds= 1.375 x I[mA] W/cm in the dipoles)

  5. RELEVANT FLUKA CAPABILITIES • Sophisticated low energy photon transport including polarization effects for Compton, photoelectric and coherent scattering, and full account for bound electron effects: already available in FLUKA since several years • New: dedicated “generic” source for SR radiation accountingfor: • Spectrum sampling • Polarization as a function of emitted photon energy • Angular distribution • Arbitrary orientation emitting particle vs magnetic field • Photon emission along arcs/helical paths

  6. SYNCHROTRON RADIATION INTERCEPTION ℓ ℓ accelerator bending radius vacuum chamber radius ℓ dipole length inside the same dipole only if ℓ > for = 9 km and = 4.5 cm ℓ > 28.5 m for = 3.1 km and = 6.5 cm (LEP2) ℓ > 20 m totally escaping for shorter dipoles shielding in the interconnects ?

  7. LAYOUT MODEL 1.5 m Q 10.5 m dipole Iron + plastic 25 mm 24 cm absorber Copper (2mm tube) water cooling Lead

  8. TOTAL POWER normalized to 10 mA beam current

  9. BEAM CHAMBER normalized to 10 mA beam current

  10. WATER normalized to 10 mA beam current values averaged along the dipole length

  11. DIPOLE COILS normalized to 10 mA beam current over 116 days/year front face masks ?

  12. DIPOLE COILS normalized to 10 mA beam current values averaged along the dipole length

  13. OZONE Adapted from NCRP Report 51 and LEP Note 379 (under the assumption of no O3decomposition, yielding in the t expression a neglected term kPeV/V with k decomposition constant equal to 1.4 10-16 cm3/eV) For P=10 W in air, V108 cm3, vent10 h  at saturation CO31-2 ppm

  14. SHIELDED BEAM CHAMBER B 3 mrad Scoring surfaces • Beam chamber: round IR = 4.5 cm • Aluminum pipe: thickness = 0.5 cm • Lead shielding: thickness = 5.0 cm • 9 km radius, Ec = 1.32 MeV

  15. GRAZING INCIDENCE EFFECT 3 mrad incidence  Radius or Depth  sin(3 mrad) (cm)

  16. THE PHYSICAL EXPLANATION The first scattering effect: after a Compton interaction the photon loses “memory” of the initial grazing incidence because of the much larger scattering angle

  17. BENDING (NO) EFFECT Vacuum Al Pb

  18. BENDING (NO) EFFECT Vacuum Al Pb

  19. SPECTRUM EVOLUTION PbKx lines Al Kx lines Annihilation

  20. REFLECTION INTO VACUUM

  21. ESCAPING POWER 100% 10% 1% Al Pb 0.1%

  22. ESCAPING RADIATION Al Pb

  23. NEUTRON PRODUCTION AND ACTIVATION Neutron production:  1.110-10 n/cm/e, 7105 n/s/cm/mA Activity at saturation:  170 kBq/cm/mA (mostly 203Pbgs/m, 26Alm,205Pbm) After 1 day:  5.5 kBq/cm/mA After 1 week:  800 Bq/cm/mA (almost only 203Pb)

  24. OPENING CONCLUSIONS • extensive calculation of synchrotron radiation is possible with full generality • as expected the attenuation curve is insensitive to the incidence angle and (unfortunately) far from naïve line-of-sight approximations • localized absorbers look as an attractive option. More realistic shape is under way (possibly integrated inside the dipoles) • which magnets? Coils on the external side of the beam would be highly exposed

  25. RESERVE SLIDES

  26. PHOTON CROSS SECTION Photoelectric dominated Compton dominated Pair dominated Compton dominated Pair dominated Photoelectric dominated p.e.=photoelectric incoh=Compton coherent=Rayleigh nuc=photonuclear N=pair production, nuclear field e=pair production, electron field

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