OPTICS UPDATE

Ulisse Bravar

University of Oxford

3 August 2004

How to tune the MICE channel

• Baseline configuration: flip modep = 200 MeV/c = 42 cm in LH Bz = 4 T in solenoids

• Steps: achieve minimum as stated: FC & CCuniform B-field inside spectrometer (to 1%): ECuniform inside spectrometer: MC

Software• Matching code from Bob Palmer:

written in QuickBasic, runs on Windows ICOOL + minimization routine ‘empty’ MICE channelparaxial tracks

• Numerical evolution of by John Cobb: ‘empty’ MICE channel from G. Penn, MuCool note 71: 2 ’’ – (’)2 + 4

2 2 – 4 = 0

• Work in progress: a) matching & minimization for Unix, ICOOL independentb) study of large amplitude tracks, with dE/dx & RF, p-spread

Present status of solutions• For every set of coil configurations: a) Determine paraxial solutions for p = 200 MeV/c, flip and no-flip

modes, = 42, 25, 17, 7 cm in LH: 8 sets of currents b) Semi flip mode obtained by combining flip & no-flip: 4 more

setsc) Stages IV and V of MICE obtained from stage VId) p < 200 MeV/c: scale solutions from p = 200 MeV/c: (8 + 4) x 2 =

24 additional sets of currentse) 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…

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 !!!

z (m)

(

m)

Bz

(T)

Optical solutions (2)

• Currents from Bob Palmer’s note, Sept. 2003Tab. 4 & 5 SFOFO = 43 cm

• 200 MeV/c looks OK:

= minimum in LH

= uniform in solenoid

• Mismatches at 180 and 220 MeV/c z (m)

Bz

(T)

(

m)

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 at p = 200 MeV/c looks OK

• Note: big increase in match coil region z (m)

Bz

(T)

(

m)

What happens at large amplitudes?

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 = 6 mm rad

momentum (GeV/c)

(

m)

What is wrong with the present coil configuration?

• 600 mm gap causes growth. Possible consequences: beam scraping, smaller momentum acceptance

• 600 mm gap causes increase. The beam that we are measuring is not the beam that we are cooling

• The smaller the gap, the better

Bob Palmer 9/2003

`M. Green 600 mm’• larger -- presumably due to increased spacing

matching – focus coils and smaller B

• Smaller momentum acceptance:off momentum muons might scrape beam aperture

Different here

Bz

Reminder

functions @ 200 MeV/c, M. Green configurations, 400, 500, 600mm

400 mm 500 mm 600 mmNew New Old

Green = - 5% solid -10% dashed Black = On momentumRed = + 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?)

functions @ 240 MeV/c, M. Green configurations, 400, 500, 600mm

400 mm 500 mm 600 mmNew New New

240 MeV/c looks ‘tidier’

Beta still rises in 2nd RF – but less than at 200 MeV/c

Emittance growth in 600 mm gap

• MICE Note 49 (Bob Palmer, September 2003)

• Present coils (Mike Green et al., March 2004)

from ecalc9f increases in drift

• Quick fix: x-px correlation in the Gaussian beam in the upstream solenoid

PROBLEM

z (m)

(

m r

ad)

Quick fix: x – px correlation

Note 49MG coils

MG coilswith

x-px correlation

z (m)

(

m r

ad)

x (m)px (GeV/c)

dE/dx and acceleration

• From Bob Palmer, June 2004

• Conclusion: Acceleration, dE/dx have no observable effect on MICE optics

momentum (GeV/c)

(

m)

MICE stages IV and V

z (m)z (m)

(

m)

Bz

(T)

Stage VStage V Stage IV

MICE stage III

z (m)z (m)

(

m)

Bz

(T)

(

m r

ad)

Flip and no-flip modes

z (m)z (m)

(

m)

Bz

(T)

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