Robust Spin Polarisation LCABD WP 2'3

1
Robust Spin PolarisationLC-ABD WP 2.3

• I. Bailey
• University of Liverpool
• Cockcroft Institute

2
heLiCal Collaborators (LC-ABD WP5.1 WP2.3)

• I.R. Bailey, P. Cooke, J.B. Dainton, T.
  Greenshaw, L.I. Malysheva (University of
  Liverpool)
• D.P. Barber (DESY)
• 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)
• E. Baynham, T. Bradshaw, A. Brummit, S. Carr, Y.
  Ivanyushenkov, J. Rochford
• (CCLRC Rutherford Appleton Laboratory)

External collaboration with EUROTeV WP3 (damping
rings) and EUROTeV WP4 (polarised positron
source).
3
Talk Outline

• Review WP 2.3 goals
• Current WP 2.3 activity
• Source Simulations
• Damping Ring Simulations
• Main Linac / BDS Simulations
• Interaction Region Simulations
• Future plans and conclusion

4
Introduction to WP2.3

• High intensity spin-polarised e- and e beams
  are essential for realising the full physics
  potential of the ILC.
• POWER report - hep-ph/0507011
• Spin-polarised e- source is already part of ILC
  baseline.
• Growing consensus for spin-polarised e source
  (see WP5.1).
• Develop reliable software tools that allow the
  machine to be optimised for spin polarisation as
  well as luminosity.
• Demonstrate that delivery of the beam
  polarisation to the interaction point can be
  robust and without loss of intensity.

5
WP 2.3 Objectives and Deliverables

• Develop specialised tools to simulate e- / e
  spin transport through each region of the ILC.
• Simulate bunch-bunch depolarisation effects at
  interaction point.
• Full cradle-to-grave ILC spin polarisation
  simulations.
• Assess degree and robustness.
• Validate simulations against experimental data.
• Assess ILC polarimetry designs.
• Deliverables
• Report detailing conclusions of cradle-to-grave
  simulations.
• Report on any additional experimental
  measurements required to validate software.
• Report on polarimetry layout.
• Simulation package itself forms main legacy.

6
Software package overview
e source
Packages in parentheses will be evaluated at a
later date.
7
Source Simulations

• Helical undulator e source
• Spin-tracking for e- beam
• Polarisation of synchrotron radiation
• Transfer of spin from g to e (conversion target)
• Spin-tracking of e through capture optics

• Capture optics
• Plan to add T-BMT into ASTRA.
• Some simulations carried out by Yuri Batygin
  (SLAC)

Also EUROTeV WP4 (Sabine R, DESY)
8
Damping Ring Simulations

• In collaboration with EUROTeV WP3 and ILC WG3b.
• ILC WG3b DR recommendation to be finalised Nov
  9th-11th.
• Choose between 7 DR lattices.
• heLiCal on track to analyse 2 representative
  lattices by early November.

Depolarisation effects expected to be small in
ideal damping ring. Magnet misalignments added to
(MAD) lattice files to give realistic simulation.
Not just theoretical minimal emittance optic.
9
(No Transcript)
10
Main Linac / BDS

• Development of simulation software 2006 / 2007.
• Monitoring status of external main linac and BDS
  groups
• Use of curved tunnel geometry?
• Current debate within ILC WG1.
• Expect approximately 560 bends of 5.7mrad (after
  energy upgrade to 500 GeV beam).
• heLiCal initial assessment
• Will lead to spin precession 1000.1 along main
  linac.
• Requirement for spin rotators.
• Effect of additional spin diffusion deemed small.
• More sophisticated calculation to follow.

11
Bunch-Bunch Interaction Simulations (1)

• Work plan
• Apply CAIN to variety of ILC parameter sets at
  500GeV and 1TeV.
• Critical review of theoretical uncertainties.
• Add further higher-order / full spin correlations
  to CAIN.
• Non-Gaussian beam profiles.
• Incoherent / coherent pair production.
• Compare with Guinea-PIG (MC) simulations.
• Preliminary indications
• Large relative difference between beam
  depolarisation obtained using different ILC
  parameter sets.
• Small absolute difference

12
Bunch-Bunch Interaction Simulations (2)
TESLA parameters
PINIT1.0
low Q parameters
PINIT1.0
Before interaction
During interaction
After interaction
13
Bunch-Bunch Interaction Simulations (3)
TESLA parameters
PINIT0.9
low Q parameters
PINIT0.9
Before interaction
During interaction
After interaction
14
Integrated Cradle-to-Grave Simulations

• Adopt common exchange format
• E.g. Ensemble of position, momentum and spin
  vectors.
• Integrated framework
• Initially generate and pass files manually.
• Work towards full automation.
• Compare with integrated orbit-tracking studies in
  other groups.
• Attempt to keep spin and orbit analyses
  compatible.

15
Summary of activity since March 2005

• Software tools for simulations identified
• Source Simulations
• Mathematica spin-transport interface to GEANT4
  (Duncan S)
• SPECTRA simulations of undulator radiation
  polarisation (Duncan S, Ian B)
• Damping Ring Simulations
• SLICKTRACK training at Daresbury / DESY for Ian
  B, Larisa M Duncan S (Des B)
• SLICKTRACK development at DESY / Daresbury (Des B
  / Larisa M)
• Damping Ring meeting between Des B, Larisa M, Ian
  B and Andy Wolski at Daresbury
• Interaction Region Simulations
• Bunch-bunch physics meeting between Des B, Gudi
  M-P, Philip Bambade, Cecile Rimbault and Kaoru
  Yokoya
• CAIN2.35 installed at Durham / Liverpool
  replacing CAIN2.1e (Gudi M-P / Ian B)
• Finished commissioning CAIN (Gudi M-P)
• Initial CAIN ILC simulations (Gudi M-P)

16
Priorities

• Some parts of spin-tracking simulation require
  additional staff effort
• Undulator (e- beam)
• Capture optics
• Main Linac
• BDS
• heLiCals response
• Focus on strengths in order to complete source,
  damping ring and beam-beam simulations on
  schedule.
• Liase with ILC WG1 and LC-ABD WP1 groups to
  identify possibilities for collaboration.
• Liase with DESY EUROTeV WP4 RA working on e
  source spin-transport (expected October 2005).

17
Future Plans (next six months)

• Continue RA PhD student SLICKTRACK training
• Complete ILC SLICKTRACK code development (for
  damping rings)
• Complete first assessment of damping ring
  depolarisation
• In collaboration with EUROTeV WP3
• Complete first assessment of CAIN ILC bunch-bunch
  simulations
• Complete initial development of all software
  tools
• Complete initial cradle-to-grave simulations

18
Future Plans (2006 onwards)

• Validate simulations using experimental data (as
  needed) - April 2006
• Evaluate theoretical uncertainties on bunch-bunch
  simulations - June 2006
• Evaluate uncertainties on cradle-to-grave
  simulations - December 2006
• Use robust simulations to optimise ILC design for
  polarised beam physics - 2007 onwards
• Tie machine simulations to HEP analyses
• Integrated quantitative understanding of how
  machine decisions impact on key analyses

19
Conclusion

• Most areas of WP2.3 show excellent progress.
• Goals will be prioritised to focus on heLiCals
  strengths.
• Efforts underway to identify possibilities for
  wider collaboration (within and beyond LC-ABD).
• WP2.3 enables range of training and experience
  for heLiCal / Cockcroft Institute / CCLRC
  personnel. E.g.
• Des Barber (DESY) 2006 spin dynamics lectures at
  Cockcroft Institute.
• 1 Liverpool / Cockcroft PhD in spin dynamics
  ongoing.
• Possibility of further PhD studentships in 2006 /
  2007.
• WP2.3 on track to make contributions to key ILC
  design debates and realise delivery of polarised
  beams.
• Important that simulations are maintained and
  applied beyond March 2007 if full potential of
  WP2.3 is to be exploited.
• Possibility for wide collaboration between all
  ILC simulation groups.