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MICE phase III

MICE phase III. M. Apollonio , J. Cobb (Univ. of Oxford). work in progress!. PHASE III Two back to back tracker solenoids , no RF cavities Never studied in any detail Assumption: step 3 can be used to: Cross-calibrate solenoids and tracking

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MICE phase III

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  1. MICE phase III M. Apollonio, J. Cobb (Univ. of Oxford) MICE Analysis Meeting

  2. work in progress! • PHASE III • Two back to back tracker solenoids, no RF cavities • Never studied in any detail • Assumption: step 3 can be used to: • Cross-calibrate solenoids and tracking • Demonstrate capability of measuring an emittance change to 1% • 1st possibility of observing cooling with solid absorber(s) • Simulation • ICOOL code • evbeta: • numerical solution of optical functions differential equations MICE Analysis Meeting

  3. U.Bravar’s study on matching revisited • Naive approach: • take M. Green’s currents for step 6 w.o. cooling channel (just so) but … 1st step: MATCHING Step VI Step III • Not just a matter of taking the whole experiment and put the two spectrometers closer (~800 mm, to be checked) • Coil matchingis an important issue !!! • Solenoids will operate differently in step 3 from steps [4,6] MICE Analysis Meeting

  4. If you keep the same coil currents you end up into troubles … Asymmetric beta functions Solution: optimize the match coil currents i.o.t. get a symmetric (well behaved) beta function b (m) vacuum flip mode z (m) MICE Analysis Meeting

  5. evbeta + MINUIT Constraints used: b = 33cm symmetrical in the solenoid regions a = 0 in the solenoid regions == b flat Force b to be ~ 60 cm in the middle of the apparatus Find the new coil currents: Variation with respect to M. Green‘s starting currents DI/I(min) ~ -30%, DI/I(max) ~ +7% CAVEAT: check current densities!!! FLIP MODE (fm), NON-FLIP MODE (nfm) MICE Analysis Meeting

  6. M.Green file ‘just so’ (no coil currents optimization) 1 -6.007 0.110 0.258 0.326 -145.400 2 -5.848 1.294 0.258 0.280 -146.900 3 -4.507 0.110 0.258 0.320 -136.800 4 -4.150 0.197 0.258 0.284 -161.340 5 -3.710 0.198 0.258 0.304 -147.550 6 -2.712 0.198 0.258 0.304 147.550 7 -2.271 0.197 0.258 0.284 161.340 8 -1.827 0.110 0.258 0.320 136.800 9 -1.670 1.294 0.258 0.280 146.900 10 -0.327 0.110 0.258 0.326 145.400 flip mode non flip mode coil current files after optimization 1 -6.007 0.110 0.258 0.326 -145.400 2 -5.848 1.294 0.258 0.280 -146.900 3 -4.507 0.110 0.258 0.320 -136.800 4 -4.150 0.197 0.258 0.284 -116.717 5 -3.710 0.198 0.258 0.304 -159.676 6 -2.712 0.198 0.258 0.304 -159.676 7 -2.271 0.197 0.258 0.284 -116.717 8 -1.827 0.110 0.258 0.320 -136.800 9 -1.670 1.294 0.258 0.280 -146.900 10 -0.327 0.110 0.258 0.326 -145.400 1 -6.007 0.110 0.258 0.326 -145.400 2 -5.848 1.294 0.258 0.280 -146.900 3 -4.507 0.110 0.258 0.320 -136.800 4 -4.150 0.197 0.258 0.284 -112.539 5 -3.710 0.198 0.258 0.304 -157.036 6 -2.712 0.198 0.258 0.304 157.036 7 -2.271 0.197 0.258 0.284 112.539 8 -1.827 0.110 0.258 0.320 136.800 9 -1.670 1.294 0.258 0.280 146.900 10 -0.327 0.110 0.258 0.326 145.400 MICE Analysis Meeting

  7. After finding the new -matched- currents we can run ICOOL sim. + ecalc9 For several materials In this study: 2 slabs of different materials soon after the first spectro and just before the second spectro Study with central absorber still to be done Li, LiH, C, Polyethilene, Be (NO Liq. H) Thickness chosen in order to ensure a total 13% reduction in p (thicker slabs result in a funny beta behavior) Withdifferentvalues ofinitial emittance Plot of de/e Cooling of 5% visibile in FLIP-mode (less cooling in NON FLIP-mode) 2nd step: study of cooling performances MICE Analysis Meeting

  8. Sketch of absorbers position in phase III absorbers MICE Analysis Meeting

  9. Parameters used in simulation Pz=207 MeV/c with a spread of 10% Initial emittances ranging from 0.1 to 1.0 (cm rad) 10000 generated muons per point (i.e. initial emittance) Lost muons: worse cases at high initial e (=1.0 cm rad) 4% (LiH, C, non flip mode) 3% (C, flip mode) MICE Analysis Meeting

  10. FLIP mode (in vacuum) • Evbeta calculation • ICOOL simulation b (m) Bz (T) Z (m) Z (m) MICE Analysis Meeting

  11. Non FLIP mode (in vacuum) • Evbeta calculation • ICOOL simulation b (m) Bz (T) MICE Analysis Meeting Z (m) Z (m)

  12. FLIP mode (LiH) • Initial emittances: • e=0.2 cm rad • e =0.25 cm rad • e =0.3 cm rad • e =0.6 cm rad • Points taken at several initial emittance values • Emittance ‘measured’ at the end of the II tracker Bz (T) b (m) Z (m) Z (m) De/e (%) Z (m) Dp/p (%) Z (m) MICE Analysis Meeting

  13. Non FLIP mode • Initial emittances: • e=0.2 cm rad • e =0.25 cm rad • e =0.3 cm rad • e =0.6 cm rad Bz (T) b (m) Z (m) Z (m) De/e (%) Z (m) Dp/p (%) Z (m) MICE Analysis Meeting

  14. Flip mode Non-flip mode LiH, Li, Be, CH, C De/e (%) De/e (%) e (cm rad) e (cm rad) 0.22, 0.26, 0.38, 0.41, 0.57 (cm rad) 0.22, 0.25, 0.35, 0.4, 0.6 (cm rad) equilibrium emittances MICE Analysis Meeting

  15. J. Cobb emittance variation initial emittance MICE Analysis Meeting

  16. NB: cooling of large emittance beam is less than expected for a given Dp/p • De/e = Dp/p * (1-e(eqm)/e) • Should reach Dp/p asymptotically for e oo • Worse behaviour in NON-FLIP mode • Investigate by removing absorbers in ICOOL • See 2-3% growth of emittance for large emittance beams w.o. absorbers • We know from UB and BP et al that norm. emittance is NOT conserved in a drift • |B| is low in drift region between 2 solenoids  Emittance growth • No simple model for this (unsatisfactory) MICE Analysis Meeting

  17. ei=0.3 cm rad ei=0.2 cm rad ei=1.0 cm rad ei=0.6 cm rad ei=0.1 cm rad Emittance growth in vacuum: NO ABSORBERS MICE Analysis Meeting

  18. De/e (%) e (cm rad) NO absorbers: emittance growth in vacuum MICE Analysis Meeting

  19. Conclusions (very tentative) • Step 3 needs a lot more study • Simple demonstration of 1% emittance measurement capability of MICE may not be easy/possible in step III (i.e. not as easy as perhaps expected) • It could be possible to observe some cooling with LiH or Li or Be absorbers, but may need correction from MC (unpleasant) • To DO list • Find optimum/better matches • Investigate emittance growth • Try placing a central absorber • Optmize thickness for absorbers MICE Analysis Meeting

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