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# MICE phase III - PowerPoint PPT Presentation

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

M. Apollonio, J. Cobb (Univ. of Oxford)

MICE Analysis Meeting

• 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

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

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

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

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

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

absorbers

MICE Analysis Meeting

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

b (m)

Bz (T)

Z (m)

Z (m)

MICE Analysis Meeting

b (m)

Bz (T)

MICE Analysis Meeting

Z (m)

Z (m)

• FLIP mode (LiH)

• Initial emittances:

• 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

• Non FLIP mode

• Initial emittances:

Bz (T)

b (m)

Z (m)

Z (m)

De/e (%)

Z (m)

Dp/p (%)

Z (m)

MICE Analysis Meeting

Non-flip mode

LiH, Li, Be, CH, C

De/e (%)

De/e (%)

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

emittance variation

initial emittance

MICE Analysis Meeting

• 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

Emittance growth in vacuum:

NO ABSORBERS

MICE Analysis Meeting

De/e (%)

NO absorbers: emittance growth in vacuum

MICE Analysis Meeting

• 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