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OPTICS OF STAGE III

Ulisse Bravar

University of Oxford

6 October 2004

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Introduction

• Agreed with Mike Green to have 800 mm gap in Stage III.

• I.e. the distance between the two spectrometers, measured from the boundaries of the match coils, is 800 mm. i) Larger gap = smaller forces.ii) Smaller gap = less beam scraping.

• This configuration can accommodate a ~10 cm thick solid absorber between the two spectrometers.

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Optic Solutions• Developed new software for beam matching.

calculated by EVOLUTION, not Monte Carlo! • Stage III optics is the first time these new routines are

being used.• Goals:

1) fix currents in solenoids and end coils, fix momentum in upstream spectrometer, fix 800 mm gap;2) tune currents in match coils to achieve desired and d/dz = 0 in downstream spectrometer;3) run both flip and non-flip configurations, p = 140, 170, 200 & 240 MeV/c.

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Coils and Currents

• test

Coils and Currents

COILS

CU

RR

EN

TS

- F

LIP

CU

RR

EN

TS

– N

O F

LIP

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Worst case forces• Peak B-fields on the coil surfaces and forces • Worst case p = 240 MeV/c• Courtesy of H. Witte

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B-field

• Top: COILS and Spectrometers in Stage III

• Bottom: Bz field

p = 200 MeV/c

Red = flip mode

Blue = no-flip mode

z (m)

Bz

(T)

r (m

)

800 mm

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Beta functions

• p = 200 MeV/c

ON-MOMENTUM

functions

Red = flip mode

Blue = no-flip mode

z (m)

r (m

)

(m

)

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Matching the p = 200 MeV/c beam

Figure of merit:

i) Measure at

100 points in 1 m of uniform B-field region in downstream spectrometer

ii) Take rms of these measurements

Red = flip mode

Blue = no-flip mode

rms

(cm

)

J (A mm-2) match coil #1

J (A mm -2) m

atch coil #2

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Off momentum

z (m)z (m)

(

m)

r (m

)

FLIP MODE NO-FLIP MODE

p = 180 MeV/c p = 200 MeV/c p = 220 MeV/c

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Icool - functions• Actual Icool beam

p = 200 MeV/c

• No more

evolution• No more paraxial

beams• Input emittance:

= 6 mm rad

Red = flip mode

Blue = no-flip modez (m)

(

m)

r (m

)

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Icool transmission and emittance

z (m)z (m)

r (m

)

r (m

)

Lo

ss (

%)

(

mm

rad

)

Loss < 0.2 % Emittance ~ constant

Flip mode p = 200 MeV/c No-flip mode

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Conclusions• We came up with a realistic layout for MICE

Stage III. • Optic solutions for all operating modes and all

momenta for this layout have been determined.• Worst case forces have been checked. • In addition, a perfect software package is now

available to deal with beam optics in MICE. • It would be straightforward to do the matching

one more time, should we decide to change the layout of Stage III.