Robust Spin Polarisation LCABD WP2'3

1
Robust Spin Polarisation LC-ABD WP2.3

• Ian Bailey
• The University of Liverpool / Cockcroft Institute

2
heLiCal Collaborators (WP5.1 WP2.3)

• I.R. Bailey, J.B. Dainton, P. Cooke, T.
  Greenshaw, L.I. Malysheva (University of
  Liverpool )
• D.P. Barber (DESY/Hamburg)
• G.A. Moortgat-Pick (University of Durham/CERN)
• J.A. Clarke, O.B. Malyshev, R.J. Reid, D.J.
  Scott, B. Todd (CCLRC ASTeC Daresbury Laboratory)
• Y. Ivanyushenkov, E. Baynham, T. Bradshaw, S.
  Carr, J. Rochford (CCLRC Rutherford Appleton
  Laboratory)

3
Talk Outline

• Review WP 2.3 goals
• Review spin polarisation physics at ILC
• Current WP 2.3 activity
• Software tools
• SLICKTRACK
• CAIN
• Future activity

4
Introduction to WP2.3

• High intensity spin-polarised e- and e beams
  are essential for realising the total physics
  potential of the ILC (hep-ph/0507011 see Gudi
  M-P talk for LC-UK on Friday)
• Delivery of the beam polarisation to the
  interaction point must be robust and without loss
  of intensity
• Develop and use reliable software tools that
  allow the machine to be optimised for spin
  polarisation as well as luminosity

5
WP 2.3 Goals

• Simulate transport of spin polarisation from e- /
  e sources to interaction region.
• Current activity.
• Simulate bunch-bunch depolarisation effects at
  interaction point.
• Current activity.
• Full cradle-to-grave LC spin polarisation
  simulations.
• Assess degree and robustness.
• Initial simulation results expected March 2006.
• Validate tools against experimental data.
• Assess LC polarimetry designs.

6
Spin Transport at the ILC
Beam Delivery System
Linac
Damping Ring
Positron Source
Linac
Undulator
150GeV e-
Intense polarised e beam
5GeV e
250GeV e
Interaction Point
Depolarisation Misalignments, EM fields,
Synchrotron radiation, resonance, bunch-bunch
250GeV e-
Beam Delivery System
Linac
Damping Ring
Electron Source
Linac
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Spin evolution (I)
Polarisation definition
where
Spin precession (Thomas-Bargmann-Michel-Telegdi)
e.g. 1mrad orbital deviation ? 65 spin
precession for 500GeV electron
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Spin evolution (II)
Synchrotron Radiation
Sokolov-Ternov effect
Spin Diffusion
Noise Inhomogeneous fields
Spontaneous polarisation

• Spin / orbit coupling
• Depolarisation

(HERA 27.5 GeV)
but damping time much shorter.
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WP 2.3 - activity in last six months

• New Liverpool RA joined group (Ian Bailey) Mar 05
• New PhD student joined/joining group (Larisa
  Malysheva) Sep 05
• Mathematica spin-transport interface to GEANT4
  (Duncan S) Ongoing
• SLICKTRACK training for Larisa M, Duncan S, and
  Ian B at Daresbury workshop (Des B) Apr 05
• Larisa M and Ian B visited DESY for further
  SLICKTRACK training (Des B) May/Jun 05
• Software tools for simulations identified
  (presented at RHUL by Larisa M) Jun 05
• SLICKTRACK development at DESY / Daresbury (Des
  B. / Larisa M,) Ongoing
• Bunch-bunch physics meeting between Des B, Gudi
  M-P, Philip Bambade, Cecile Rimbault and Kaoru
  Yokoya Jun 05
• CAIN2.35 installed at Durham / Liverpool
  replacing CAIN2.1e (Gudi M-P / Ian B) Ongoing

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Software packages
Packages in parentheses will be evaluated at a
later date.
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New since December 04!
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Transfer matrix
Transfer matrix evolves spin and orbit
co-ordinates from one dipole to the next.
Ignores deviations of orbit due to spin
(Stern-Gerlach).
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Bunch-bunch status

• Guinea-Pig
• Monte-Carlo simulation
• Depolarisation effects to be included based on
  CAIN formalism(July 2006 / March 2007)
• Will spin be part of Monte-Carlo?
• CAIN
• Version 2.35 installed at Daresbury (windows) and
  Durham (linux)
• Initial tests show some disagreements
• Modification need to beam profile routines?
• Is present combination of T-BMT and S T
  sufficient for ILC bunch structure?
• Gyromagnetic anomaly modified by higher-order QED
  processes?
• Only ILC depolarisation work currently ongoing is
  LC-ABD WP2.3

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Miscellaneous Issues

• Develop a framework for interfacing software
  tools (c.f. Glen Whites work)
• Add spin transport to ASTRA
• Runge-Kutta integration of T-BMT
• Model depolarisation of e- beam in undulator
• Spin transport being added to GEANT4 by DESY
  Zeuthen (EUROTeV WP4)

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WP 2.3 Activity for next six months

• Continue RA PhD student SLICKTRACK training
  (Des B in Lancaster next week)
• Nov 05
• Complete ILC SLICKTRACK code development
• Dec 05
• Complete first assessment of damping ring
  depolarisation
• In collaboration with EUROTeV WP3
• Compare with previous Wolski and Bate paper
  (MERLIN)
• Dec 05
• Finish commissioning CAIN
• Aug 05
• Complete first assesment of CAIN ILC bunch-bunch
  simulations
• Dec 05

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Conclusions

• Identified software tools for all ILC regions
• Tools being assessed / developed
• Suitable framework must be identified
• On track to reach all goals
• Busy six months ahead

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Additional Slides
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Summary of storage ring computer codes
Linearised orbital and spin motion
Linearised orbital, 3-D spin motion
Monte Carlo simulation
SITROS
SLIM
SMILE
SODOM
SLICKTRACK
SLICK
SITF
Non-linear orbital, 3-D spin motion
SpinLie
MERLIN