Tracking studies of the CLIC BDS

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Tracking studies of the CLIC BDS

• Javier Resta Lopez
• Takao Asaka
• Angeles Faus-Golfe
• Daniel Schulte
• Frank Zimmermann

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Contents

• Introduction
• CLIC BDS layout and optics
• Tracking codes
• Chromatic effects ( qualitative and quantitative
  analysis)
• Performance of the linear system
• Tracking studies for an alternative nonlinear
  collimation system
• Beam sizes at the spoiler
• Particles distribution at the spoiler
• Luminosity performance
• Outlook

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IntroductionCLIC BDS layout and optics
entrance

ß-CS
E-CS
FFS
IP
Dx (m)
ß1/2 (m1/2)
More details see talk from Frank Zimmermann
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IntroductionTracking codes
Entrance
IP
Importance of the benchmarking of codes
Guinea-Pig
Multiparticle tracking
Optics lattice
Beam-beam interaction
transport
performance
MAD Placet SAD
Lie
Other codes see talk from Stefano Redaelli
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Chromatic effects FFS
The center of the ellipse is determined by the
Taylor map
Transport formalism
For the FFS a description up to second order is
enough !
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Chromatic effects CS
1s
3s
The center of the ellipse
in this case R160. and R260.
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Chromatic effectsBDS
The center of the ellipse
The Taylor map up to 3rd order gives a good
description of the center ellipse transport in
phase space for d 0.3
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Chromatic effects
Beam profile at the IP
Residual horizontal dispersion at the IP
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Chromatic effects
Phase space at the IP
Particles with lower energy than the nominal one
(1500 GeV) contribute strongly to the tails of
the transversal phase space
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Chromatic effects
Polinomial fit to tracking data
x µm
1st, 2nd and 3rd order pure chromatic
coefficients
x µrad
1st, 2nd order matrix elements from direct
calculation with MAD
Third order chromatic aberrations can be built
from the aberrations at second order times
d??/?0 for instance, U1666 is related with
T116 D2, where D is dispersion
d0?E/E0
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Performance
Luminosity as a function of the beam energy
spread from the tracking with Placet, MAD and
SAD. The values have been normalized to the value
given by Placet at 0 energy spread without
synchrotron radiation.
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Tracking studies for an alternative nonlinear
collimation system
CLIC BDS with energy nonlinear collimation
section
1
Testing two different configurations for energy
nonlinear collimation
spoiler
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Skew sextupole
Skew sextupole
See details from Angeles Faus talk
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Tracking studies Beam size at the spoiler

• The first skew sextupole is used to increase
  the vertical beam size at the spoiler. This
  allows us to collimate using a bigger collimator
  half gap, so as to guarantee collimator survival
  in case of beam impact.

1
Vertical beam size
Horizontal beam size
Average energy offset
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Tracking studies Particles distribution at the
spoiler
1
2
For an average energy offset d00.01
spoiler half gap
ax0.888 mm ay1.835 mm
ax2.21 mm ay8.349 mm
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Tracking studies Luminosity as function of the
skew sextupole strength
2
1
For Ks104 m-2 the luminosity decreases almost
two orders of magnitude with respect to the
value for Ks0.0
Better performance for different scenarios
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Tracking studies Particles distribution at the
spoiler
1
Horizontal plane
d01
in this case the sextupole reduces the
horizontal beam size at the spoiler for d0 2.5
. Not desired effect !
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Tracking studies Particles distribution at the
spoiler
2
Horizontal plane
d01
ax2.21 mm
smooth increase of the horizontal beam size
Collimation cut
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Tracking studies Particles distribution at the
spoiler
1
Vertical plane
d01
expected behavior !
ay1.835 mm
Collimation cut
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Tracking studies Particles distribution at the
spoiler
2
Vertical plane
d01
expected behavior !
ay8.349 mm
Collimation cut
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Tracking studies Outlook
2
1

• No bending magnet between the skew sextupoles
  effective geometric aberrations cancellation
• Better performance for different scenarios.
  Improvement possibility.
• Bad collimation efficiency !

• Bending magnets between the skew sextupoles
  impair the geometric aberrations cancellation
• Bad performance.
• Good collimation efficiency !

Next step find an optics solution between both
configurations !