Liverpool Accelerator Physics Review

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Liverpool Accelerator Physics Review

• Ian Bailey
• Xmas 2005

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Our Group

• Ian Bailey, John Dainton, Tim Greenshaw, Leo
  Jenner, Larisa Malysheva, Duncan Scott
• Peter Cooke, Peter Sutcliffe

Our Work

• Current projects focus on development of
  International Linear Collider (ILC)
• Within the context of the Cockcroft Institute

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Cockcroft Institute
The University of Liverpool is the lead
organisation in the newly formed national centre
for accelerator science - the Cockcroft
Institute. Liverpools partners in the Cockcroft
Institute are the universities of Lancaster and
Manchester, Daresbury Laboratory (CCLRC) and the
North West Development Agency (NWDA).

• Our inaugural year!
• New Liverpool staff
• 2005 - Larisa, Leo and Ian
• 2006 - 1 Lecturer and 1 RA already hired
• New building (finished soon!)
• New director
• New academic and research programmes

http//www.lancs.ac.uk/cockcroft-institute/default
.htm
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The International Linear Collider
Interaction Regions

• TeV-scale high-luminosity (2 1034 cm-2s-1)
  e-e linear collider.
• High-precision measurements of electroweak
  physics.
• Clean channels for direct and indirect searches.
• Complementary physics programme to the the LHC.
• Many technological challenges
• How to produce sufficient positrons?
• How to produce a beam with such low emittance at
  the IP?

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Undulator-Based Positron Source
ILC WG3a recommended helical undulator as
baseline solution for positron source! (ILC
workshop, Snowmass, August 2005)
See Duncan Scotts Talk for Proof-of-Principle
Baseline layout of ILC with undulator at 150GeV
position in main linac.
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Introduction to Helical Undulators

• Helical undulator insertion devices
• Magnetic dipole field rotates along length of
  undulator
• Charged particles describe helical trajectories
  within undulator
• Emit intense circularly-polarised synchrotron
  radiation on axis

• Commonly used in light-sources
• ESRF (France), JAERI (Japan), Stanford (US),
  Novosibirsk (Russia) , ALS (US), CLS (Canada),
  SRS (UK),

• heLiCal collaboration developing and evaluating
  two undulator designs for ILC
• Superconducting
• Permanent-magnet

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heLiCal Collaboration

• 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 RAL)

• Part of both the UK-based LC-ABD initiative and
  EUROTeV. Collaborates with Cornell University.
• Mandated to design a helical undulator as part of
  a spin-polarised positron source for the ILC.
• Short (30cm) superconducting and permanent
  magnet prototypes have been constructed at RAL/
  Daresbury/ Liverpool.
• First measurements of field quality completed.
  Additional DAQ systems under construction.
• Decision made to construct and test long (4m)
  superconducting undulator module.
• Decision endorsed by international LC-ABD review
  panel (October 2005).

Superconducting undulator prototype
Permanent magnet undulator prototype
Preliminary design of long superconducting
undulator prototype
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Conversion Target
Liverpool heads EUROTeV-funded task to design a
conversion target and photon collimator for the
polarised positron source.

• Working in collaboration with SLAC and LLNL.
• Developing water-cooled rotating wheel design.
• 0.4 radiation length titanium alloy disc / rim.
• Radius between 1 m and 2 m.
• Rotates at approximately 1000rpm.

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Spin Transport

• 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.
• 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.

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heLiCal Collaboration

• Developing reliable software tools that allow
  the machine to be optimised for spin polarisation
  as well as luminosity. Aiming to carry out full
  cradle-to-grave simulations.
• Currently carrying out simulations of positron
  source and depolarisation effects in damping
  rings and during bunch-bunch interactions.
• Damping ring simulations recently presented at
  CERN ILC damping ring workshop.
• Will soon extend simulations to cover BDS, main
  linac, etc.
• Will address key questions such as impact of
  tunnel curvature, positions of polarimeters, etc.
• In process of recruiting new staff and actively
  seeking new collaborators.

Energy spectrum and circular polarisation of
photons from helical undulator.
Trajectories of electrons through helical
undulator.
Example of SLICKTRACK simulation showing
depolariation of electrons in a ring.
See Larisa Malyshevas Talk
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Linear Accelerator Beam Diagnostics

• You cant just smash any old bunches of particles
  into each other!
• Off-energy / stray particles can potentially
  damage the delicate machinery especially at 1
  TeV!
• Beam Delivery System
• Collimation to remove stray particles
• Betatron Measurement to measure the
  instantaneous beam size (dependent on magnets,
  errors, position)
• Energy Spectrometer to measure beam bunch
  energy
• Beam Switchyard to send off-energy bunches to a
  the beam dump
• Skew Correction to correct for earlier magnet
  manufacturing/positional errors
• Emittance Measurement to measure the natural
  beam size (constant everywhere in the machine)

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ATF, ATF2, ILC
ATF at KEK, Japan is the ideal place to test and
perfect measurement and correction techniques
The ATF2 accelerator extension is being
designed specifically with the intention of
creating a test-bed for ILC like beam parameters
ILC will have two interaction points that are
downstream from the beam dump and beam delivery
system
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Some Optics design using MAD

• Modular Accelerator Design is a simple program
  that tracks beam parameters (XY size,
  dispersion, position etc) through magnetic
  elements in space and time. It has optimisation
  routines built in to minimise beam size, beamline
  length etc.
• The entire beamline will eventually be
  simulated in this way.

x y
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Some Optics design using MAD

• Energy Spectrometer Dog Leg - the beam is
  bent off course then bent back again, the energy
  can be determined by the amount of bending a
  fixed magnet achieves.

Skew Correction (0-130m) and Emittance
Measurement (130-200m) Section Tunable, rotated
quadrupoles correct for magnet errors. Four wire
scanners then measure the beam size in
independent phases.
x y
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Conclusion

• Liverpool has a new accelerator group!
• The UK has a new accelerator institute!
• Actively collaborating in key areas of ILC RD
• Positron Source
• Spin Transport
• Beam Delivery System
• Building accelerator expertise.
• Preparing for a busy 2006
• LCWS06 - Bangalore, India
• EPAC - Edinbugh, UK
• SPIN2006 - Japan
• Its time for a holiday
• Merry Xmas!