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OPTICS UPDATE

OPTICS UPDATE. Ulisse Bravar University of Oxford 3 August 2004. How to tune the MICE channel. Baseline configuration: flip mode p = 200 MeV/c b ^ = 42 cm in LH B z = 4 T in solenoids Steps: achieve minimum b ^ as stated: FC & CC

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OPTICS UPDATE

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  1. OPTICS UPDATE Ulisse Bravar University of Oxford 3 August 2004

  2. How to tune the MICE channel • Baseline configuration: flip mode p = 200 MeV/c b^ = 42 cm in LH Bz = 4 T in solenoids • Steps: achieve minimum b^ as stated: FC & CC uniform B-field inside spectrometer (to 1%): EC uniform b^ inside spectrometer: MC

  3. Software • Matching code from Bob Palmer: written in QuickBasic, runs on Windows ICOOL + minimization routine ‘empty’ MICE channel paraxial tracks • Numerical evolution of b^ by John Cobb: ‘empty’ MICE channel b^ from G. Penn, MuCool note 71: 2 b^ b^’’ – (b^’)2 + 4 b^2k2 – 4 = 0 • Work in progress: a) matching & minimization for Unix, ICOOL independent b) study of large amplitude tracks, with dE/dx & RF, p-spread

  4. Present status of solutions • For every set of coil configurations: a) Determine paraxial solutions for p = 200 MeV/c, flip and no-flip modes, b^ = 42, 25, 17, 7 cm in LH: 8 sets of currents b) Semi flip mode obtained by combining flip & no-flip:4 more sets c) Stages IV and V of MICE obtained from stage VI • p < 200 MeV/c: scale solutions from p = 200 MeV/c: (8 + 4) x 2 = 24 additional sets of currents e) p = 240 MeV/c: scale FC and CC, repeat matching:12 more currents • So far, have several of the solutions from first line. Also, solutions for reduced gaps: 400 mm, 500 mm…

  5. Optical solutions (1) • MICE proposal to RAL (2003): • coil configuration from tab. 4.1 • currents from tab. 4.2, case 1a • p = 220 MeV/c • p = 200 MeV/c • p = 180 MeV/c • MISMATCH for p = 200 MeV/c !!! Bz (T) b^ (m) z (m)

  6. Optical solutions (2) • Currents from Bob Palmer’s note, Sept. 2003 Tab. 4 & 5 SFOFO b^ = 43 cm • 200 MeV/c b^ looks OK: b^ = minimum in LH b^ = uniform in solenoid • Mismatches at 180 and 220 MeV/c Bz (T) b^ (m) z (m)

  7. Optical solutions (3) • Coil configuration from Mike Green and INFN-GE agreed upon at CERN 2004 meeting • 600 mm GAP • Currents determined with Bob Palmer’s minimization routine • Again b^ at p = 200 MeV/c looks OK • Note: big b^ increase in match coil region Bz (T) b^ (m) z (m)

  8. What happens at large amplitudes? • b^ in the centre of LH cell • Flip mode, p = 200 MeV/c • From Bob Palmer, June 2004 • Optical solutions with paraxial rays work fine for beams with e^ = 6 p mm rad b^ (m) momentum (GeV/c)

  9. What is wrong with the present coil configuration? • 600 mm gap causes b^ growth. Possible consequences: beam scraping, smaller momentum acceptance • 600 mm gap causes e^ increase. The beam that we are measuring is not the beam that we are cooling • The smaller the gap, the better

  10. Different here Reminder Bz b • `M. Green 600 mm’ • blarger -- presumably due to increased spacing matching – focus coils and smaller B • Smaller momentum acceptance: • off momentum muons might scrape beam aperture Bob Palmer 9/2003

  11. b functions @ 200 MeV/c, M. Green configurations, 400, 500, 600mm 400 mm 500 mm 600 mm New New Old Green = - 5% solid -10% dashed Black = On momentum Red = + 5% solid +10% dashed Beta always > 1.8 metres in 2nd RF for p = 1.1 x ptune Decreased spacing helps beta-stability ‘400mm’ not as stable as Palmer solution (not buildable?)

  12. b functions @ 240 MeV/c, M. Green configurations, 400, 500, 600mm 400 mm 500 mm 600 mm New New New 240 MeV/c looks ‘tidier’ Beta still rises in 2nd RF – but less than at 200 MeV/c

  13. Emittance growth in 600 mm gap • MICE Note 49 (Bob Palmer, September 2003) • Present coils (Mike Green et al., March 2004) e^ from ecalc9f increases in drift • Quick fix: x-px correlation in the Gaussian beam in the upstream solenoid PROBLEM e^ (p m rad) z (m)

  14. Quick fix: x – px correlation e^ (p m rad) Note 49 MG coils MG coils with x-px correlation x (m) px (GeV/c) z (m)

  15. dE/dx and acceleration • From Bob Palmer, June 2004 • Conclusion: Acceleration, dE/dx have no observable effect on MICE optics b^ (m) momentum (GeV/c)

  16. MICE stages IV and V Stage V Stage V Stage IV Bz (T) b^ (m) z (m) z (m)

  17. MICE stage III Bz (T) b^ (m) e^ (p m rad) z (m) z (m)

  18. Flip and no-flip modes b^ (m) Bz (T) z (m) z (m)

  19. Conclusions • Optical matching technique works fine, software upgrades in progress • 48 optic solutions for every coil configuration, for stage VI only. Currents will be updated as necessary • 450 mm gap looks better than 600 mm, but how good is good enough? • Need decision on B-field in spectrometer when p < 200 MeV/c

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