Post on 22-Dec-2015
04/01/2006 MICE Analysis Meeting 1
MICE phase IIIMICE phase III
M. Apollonio, J. Cobb (Univ. of Oxford)
04/01/2006 MICE Analysis Meeting 2
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
!
04/01/2006 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 …
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
04/01/2006 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
(m
)
z (m)va
cuum
flip
mod
e
04/01/2006 MICE Analysis Meeting 5
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)
04/01/2006 MICE Analysis Meeting 6
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
04/01/2006 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) 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
04/01/2006 MICE Analysis Meeting 8
absorbers
Sketch of absorbers position in phase III
04/01/2006 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 (=1.0 cm rad)
4% (LiH, C, non flip mode) 3% (C, flip mode)
04/01/2006 MICE Analysis Meeting 10
FLIP mode (in vacuum)
Evbeta calculation ICOOL simulation
Z (m)Z (m)
(m
)
Bz
(T)
04/01/2006 MICE Analysis Meeting 11
Non FLIP mode (in vacuum)
Evbeta calculation ICOOL simulation
(m
)
Z (m)Z (m)
Bz
(T)
04/01/2006 MICE Analysis Meeting 12
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 (
%)
04/01/2006 MICE Analysis Meeting 13
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 (
%)
04/01/2006 MICE Analysis Meeting 14
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)
04/01/2006 MICE Analysis Meeting 15
J. C
ob
b
initial emittance
em
itta
nce
va
riat
ion
04/01/2006 MICE Analysis Meeting 16
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)
04/01/2006 MICE Analysis Meeting 17
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
04/01/2006 MICE Analysis Meeting 18
(cm rad)
(%
)
NO absorbers: emittance growth in vacuum
04/01/2006 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