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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