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M. Apollonio University of Oxford

update on STEP III

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the case for STAGE III

first demonstration of cooling with solid absorber(s) ?

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Matching Coils currents

Set up a procedure to find the right MC currents for a matched beam:a) (trk1-2)=1/, =0b) fix (min)

Z (m)

Chosen configuration must comply with coil/physics constraints:1- max current2- temp. margin3- (min) minimise m.s.

B (

T)

(m

)

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800 mm

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800 mm

T=97.9 % T=98.4 %

emi=10 mm rad(a) (b)

(a)

(b)

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NB: beta_min = 49 cm (was 60cm at CM14)

means M1 1.4x, M2 0.7xmain issuesa)current increase: is it within

tolereances?b)magnet forces?c)MC distance = 800 mm. Can it be

changed?

300 A!

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emittance growth in vacuum

Z (m)

T (f

inal

)/ T

(in

itia

l)

i=1.0 cm rad

0 1 2 3 4 5 6

T/T=2.8%

2.8 %T/

T Z (m)

T (cm rad)

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xqByPxPxqB

PqBx

xPxPP

qBxP

P

qBxP

P

PxPP

P

xPcm

xxxy

xy

xyz

zx

z

zy

z

xxx

z

xNN

2

2222

: emittance evolution in a cylindrical symmetric channel

non uniform Bz can cause growth (e.g. flip region)

Z (m)

T (

m r

ad)

ecalc9

MUC-NOTE 0071 prediction

Most of the effect explainedMost of the effect explained

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(a) 13 cm LiH absorber in the middle

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-7.3%

-3%

-3%

Pz vs Zemi vs Z

Beta= 70cm

Beta= 50 cm

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(b) 13 cm LiH absorber in the II solenoid

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vacuum (no absorbers)

LiH absorberLiH absorber - vacuum

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00

1

eq

p

p

00

1

eq

p

p

equilibrium

vacuum growth subtracted

emi. % variation

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Conclusion

1)Slow B flip emi growth. Has to be minimized

2)a single absorber seems to work better

3) the middle point cannot have a low beta cooling effect reduced

4) reduce beta_centre increase M1 currents forces

5) better to place abs inside the II solenoid

uneasy6) transmission: large radius spool

piece doesn’t seem to create dramatic effects