towards an extremely-flat beam optics with large crossing angle for the lhc
DESCRIPTION
Warsaw, 25 th April 2012. Towards an extremely-flat beam optics with large crossing angle for the LHC. José L. Abelleira, PhD candidate EPFL, CERN Beams dep. Supervised by F. Zimmermann, CERN Beams dep. - PowerPoint PPT PresentationTRANSCRIPT
Towards an extremely-flat beam optics with large crossing angle for the LHC
José L. Abelleira, PhD candidate EPFL, CERN Beams dep. Supervised by F. Zimmermann, CERN Beams dep.
Thanks to: S. Fartoukh, S.Russenschuck (CERN), D.Shatilov (BINP SB RAS,Novosibirsk), R. Tomas (CERN), C. Milardi, M. Zobov (INFN/LNF, Frascati (Roma))
Warsaw, 25th April 2012
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Contents
• Flat beam optics. Comparison.• Double half-quadrupole• Large Piwinski angle & crab-waist collisions• Luminosity• Future work, open questions• Conclusions
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Flat beam optics
Peak luminosity
To increase luminosity:-Reduce both σx
* and σ y*
-Substantially reduce σy*
Δμx Δμy
sext1sext2sext3
π/23π/2π/2
ππ/2
5π/2
FfnNLyx
b**
2
4 Local chromatic correction in Y.
First time ever for LHC!
sext1 sext2 sext3
Chromatic correction
βx*=1.5 m
βy*=1.5 cm
βx*βy
*=15cmx15cm (nominal ATS optics with crab cavities)
Crab –waist collisions
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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45 mm
Large crossing angle-> large Piwinski anglex
z
2
15σy
15σx
σx/ σy=10 Minimum required according to beam-beam simulations.
2 mrad
Reference orbit
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Actual LHC optics
IPThe 2 beams see opposite gradients
+ +
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Flat beam LHC optics
IP
The 2 beams see the same gradients
- + - +How to produce opposite
gradient in the same pipe?
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Double half-quad
-0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08-0.08
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B0=-5.8 T g=115 T/m
NbTi
S.Russenschuck
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Kick due to the dipolar term
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Matching
Arc (MQ11)Arc (MQ11)
βx=127 mβy=21 mDx=1.5 m
βx=20 m βy=207 mDx=0.6 m
DSMSFF
Separation bending magnets
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Large Piwinski angle
Luminosity reduction through F but…1-Decrease overlapping area. Lower βy decrease
;y
yNL
;1 2
yx
yy
N;)1( 2
x
xN
x
z
2
Head-on or small φ
zCS
Large Piwinski angle
xCS2
Hourglass effect limits βy decrease CSy
cmx 12
!
2-More particles N for the same beam-beam tune shift3-It opens the possibility for crab-waist collisions
Collision section (CS)
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Crab-waist collisions
Normal collision scheme
Crab-waist collision scheme
With Large Piwinski Angle Collision Point ≠ Interaction Point P.Raimondi,
D.Shatilov, M. Zobov
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Crab-waist collisions
Conditions
)12(2
n
m
y
x
yy
xxskl
*
* /Sextupole strength
In particular25
y
x
mlmk
s 80313.0 3
2
2
2
202
y
x
P.Raimondi, D.Shatilov, M. Zobov
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Crab-waist simulationsResonance suppression
CW = 0
CW = 0.5
Dmitry Shatilov Mikhail Zobov
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Luminosity gainNx10 11\εn(μm)
3.75 3.5 3 2.5 2.21.15 0.6262 0.6721 0.7868 0.947 1.07761.5
1.0653 1.1435 1.3387 1.6111 1.83342 1.8939 2.0328 2.3798 2.8642 3.2594
2.52.9592 3.1763 3.7185 4.4753 5.0928
34.2613 4.5738 5.3546 6.4444 7.3336
Luminosity (1034 cm-1s-1 )
Nx10 11\εn(μm)3.75 3.5 3 2.5 2.2
1.151.1991 1.2938 1.5294 1.8563 2.1217
1.5 2.04 2.2012 2.602 3.1581 3.60972
3.6266 3.9132 4.6257 5.6144 6.41732.5
5.6666 6.1143 7.2276 8.7725 10.0273
8.16 8.8046 10.4078 12.6324 14.4389
Main limitation: the crossing angle due to the separation of the double half quadFurther improvements in the double half-quad. design can reduce the crossing angle (Nb3Sn)
mrad4
mrad2
θ/2= 2 mradθ/2=1 mrad
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Flat emittance
Limitation: aperture of the half quadSolution: reduce εy keeping constant εx εy
ε βhqεσ hq σ hq βy
*εx
εyβhq
Squeeze of the emittance ellipse
βy increase in the half-quad.->reduction on σy*= sqrt(εy βy
*)
βx decrease in the half-quad.->reduction of horizontal chromatic aberrations-> increase on σx
*= sqrt(εx βx*)
->Geometric reduction factor increased F=(1+ (ϴ/2)σz /σx)-1/2
Luminosity increase through significant σy* reduction and F increase
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Flat emittance
Luminosity
Keep εxεy constant and vary εx/εy
Θ=4 mrad N=2x1011
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Work in the next months
– Study of the aberrations– Rematch the dispersion– Improvement of the half-quad– Dynamic aperture– Beam-beam simulations
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Open questions
– Field quality of the double half-quad & correction scheme– Dispersion matching for the chromatic correction– 2nd order dispersion cancellation
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Conclusions• An extremely-flat beam optics (βy
*/βy*=100) is conceptual possible
for LHC– Large Piwinski angle, to reduce the collision area and allow for a
lower βy decrease– Local vertical chromatic correction– Possibility to have crab waist collisions that can increase
luminosity and suppress resonances– Can accept higher brightness.
• The performance of the new optics can be improved– Future half-quad designs (Nb3Sn)– Using a flat emittance– HE-LHC? Already flat emittance due to SR
Jose L. Abelleira. Towards an extremely-flat beam optics with large crossing angle for the LHC.
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Thank you…
…For your attention