MICE phase III

04/01/2006 MICE Analysis Meeting 1

MICE phase IIIMICE phase III

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


Simulation ICOOL code evbeta:

numerical solution of optical functions differential equations

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)

work in pro

gress

!


U.Bravar’s study on matching revisited Naive approach:

take M. Green’s currents for step 6 w.o. cooling channel (just so) but …

Not just a matter of taking the whole experiment and put the two spectrometers closer (~800 mm, to be checked)

Coil matching is an important issue !!! Solenoids will operate differently in step 3 from steps [4,6]

1st step: MATCHING

Step VI

Step III


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

(m

)

z (m)va

cuum

flip

mod

e


evbeta + MINUIT Constraints used: = 33cm symmetrical in the solenoid regions in the solenoid regions == flat Force to be ~ 60 cm in the middle of the apparatus

Find the new coil currents: Variation with respect to M. Green‘s starting currents I/I(min) ~ -30%, I/I(max) ~ +7% CAVEAT: check current densities!!!

FLIP MODE (fm), NON-FLIP MODE (nfm)


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

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 -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

M.Green file ‘just so’ (no coil currents optimization)

flip mode

non flip mode

coil current files after optimization


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) With different values of initial emittance

Plot of d/ Cooling of 5% visibile in FLIP-mode (less cooling in NON FLIP-mode)

2nd step: study of cooling performances


absorbers

Sketch of absorbers position in phase III


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 (=1.0 cm rad)

4% (LiH, C, non flip mode) 3% (C, flip mode)


FLIP mode (in vacuum)

Evbeta calculation ICOOL simulation

Z (m)Z (m)

(m

)

Bz

(T)


Non FLIP mode (in vacuum)

Evbeta calculation ICOOL simulation

(m

)

Z (m)Z (m)

Bz

(T)


FLIP mode (LiH) Initial emittances: =0.2 cm rad =0.25 cm rad =0.3 cm rad =0.6 cm rad

Points taken at several initial emittance values

Emittance ‘measured’ at the end of the II tracker

Z (m)

Z (m)

Z (m)Z (m)

(m

)

Bz

(T)

/

(%

)p

/p (

%)


Non FLIP mode Initial emittances: =0.2 cm rad =0.25 cm rad =0.3 cm rad =0.6 cm rad

Z (m)

Z (m)

Z (m)Z (m)

(m

)

Bz

(T)

/

(%

)p

/p (

%)


LiH, Li, Be, CH, C

0.22, 0.26, 0.38, 0.41, 0.57 (cm rad) 0.22, 0.25, 0.35, 0.4, 0.6 (cm rad)

Non-flip modeFlip mode

equilibrium emittances

/

(%

)

/

(%

)

(cm rad) (cm rad)


J. C

ob

b

initial emittance

em

itta

nce

va

riat

ion


NB: cooling of large emittance beam is less than expected for a given p/p / = p/p * (1-(eqm)/) Should reach p/p asymptotically for 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)


i=0.1 cm radi=0.2 cm radi=0.3 cm radi=0.6 cm radi=1.0 cm rad

Em

ittan

ce g

row

th in

vac

uum

:N

O A

BS

OR

BE

RS


(cm rad)

(%

)

NO absorbers: emittance growth in vacuum


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

Documents

MICE phase III