WP9 : Cavity BPM spectrometry

1
WP9 Cavity BPM spectrometry

• Royal Holloway
• S. Boogert G. Boorman
• University College London
• D. Attree, A. Lyapin, B. Maiheu M. Wing
• Cambridge University
• M. Slater, M. Thomson D. Ward

2
Politics and funding

• Poorly funded by PPARC
• Guaranteed funding only for FY07/08
• Enough to complete main project objectives
  including hardware commitments
• Keep all key staff
• Beyond FY08
• Start losing key staff
• Lose ability to construct new devices such as
  BPMs
• Overall can bring spectrometer work to a viable
  scientific conclusion end of 2008
• Without additional funding in 2008
• Focus more on existing ILC test systems such as
  ATF2
• BPM work from machine optimisation point of view
  opposed to energy measurement

3
Future of ESA and ATF

• Complete ESA WP4.2/9 cavity system
• Currently one dipole and one monopole cavity
  constructed
• Complete with electronics and digitisation
• Calibration (2-axis mover system)
• Complete whole system with 2 additional BPMs
• Probably same design (manufacturing costs)
• Triplet tests essential to determine performance
  of BPM design
• Triplet best configuration for spectrometer tests

• ATF1/2 program
• Collaboration with SLAC/KEK has been very
  productive for UK groups.
• Work on nanoBPM will be wound down
• Continue some development on ATF2 cavity systems
• UK leads in processing algorithms and analysis
• UK in position to provide complete cavity signal
  possessing for ATF2

4
End station A
Old SLAC BPMs
LCABD BPMs
Dipole

• Must complete energy spectrometer prototype
• Electronics for one cavity completed
• Prototype cavities (dipole and reference
  complete)
• Also simulations well advanced
• Must mine existing simulations developed within
  task 4.2
• BDSIM/Geant4
• Cavity and electronics simulation

5
Cavity construction
Dipole cavity
Reference cavity

• RF Bench tests of the new cavities next few weeks
• Beam tests at End Station A in July
• Second iteration design might be required
• Modifications might be possible (as more
  detectors are required)
• Complete system (spectrometer triplet)
• ATF2 laserwire jitter removal (see later)

6
ATF2 (Cavity BPMs)
C-band ATF2 cavity

• ATF2 will have a large deployment of cavity BPMs
• Basic design by A. Lyapin (modified by Y. Honda
  et al.)
• Essential for ATF2 final focus optimisation
• Groups relying on beam steering algorithms to
  obtain 35 nm focus spot size
• Electronics and processing essentially same as
  nanoBPM
• Must help convert knowledge of ATF-nanoBPM and
  ESA BPMs to normal operation of ATF2
• ATF2-FF S-band cavities!

20 cavities 50 nm resolution Main beam
steering/alignment diagnostic
7
Turn key diagnostic
Cavity (2.8 GHz)

• Cavity BPMs intended to be turn key diagnostics.
• Requires a significant amount of processing
  (unlike button and strip-line BPMs)
• Two possible methods for readout.
• Mix to base-band
• Automatic electronics control, phase etc.
• Fixed processing scheme
• Mix to 100 MHz and digitise
• Further digital signal processing required
• Very flexible (algorithms can be modified etc)
• Can be fast

Mixer (IF 20MHz)
100MHz digitiser
I-Q. position/tilt
PC processing
8
RF electronics development

• Development of printed circuit board mix down
  electronics essential
• Reduces costs
• RF component cost
• Power distribution
• Form factor
• Stable solution once proven (less connectors,
  cables etc)
• Less flexible for future modifications
• Difficult to change filters/limiters etc
• Not all components are simple ICs (couplers,
  limiters etc)

WP4.2 electronics
ATF2 electronics
9
Cavity signal processing
Multi-bunch data from nanoBPM

• Many groups considering FPGA based processing
• Well suited to the digital signal processing
  problem
• Commercial options available
• LBNL and FNAL have board designs
• Problem is with the firmware/processing
• Solution also being considered for HOM-BPMs
• Also well suited for data reduction required for
  full train BPM analysis
• Collaborations being formed to look at these
  solutions for BPM work

FNAL design VME, ADC/FPGA/DAC board
AO
FPGA
AI
10
Integration with laserwire systems

• Beam position jitter might ruin laserwire system
  measurements
• 1 micron electron beam size
• Subtract beam jitter requires lt100nm resolution
• Instrument one laserwire IP with two BPM systems.
• Either side of laserwire systems
• Existing S-band design quite applicable
• Calibration and monitoring a problem
• Triplet formed by laserwire (acts a little like a
  slow BPM)
• Construct two for next phase of laserwire
  operations?

Existing SL-BPMs in ATF laserwire
Laserwire interaction point
11
Spectrometer simulation studies

• Simulation work was neglected in favour of BPM
  development work in LCABD1
• Simulation of BDS from linac exit to interaction
  region
• Effect of background on spectrometer measurement
• Beam halo
• Energy loss due to Synchrotron radiation
• Tools are complete
• Geant4 for tracking in dipole field maps
• BDSIM simulation of whole delivery
• Must now get results from our tools

12
Summary

• Limited funds from PPARC/JAI
• Re-evaluate goals of WP9
• Complete system at SLAC and operate with a full
  triplet system
• Develop cheaper mixer electronics
• Turn key operation of cavity systems
• FPGA based processing/algorithms
• Become more involved in ATF2 BPM systems
• Complete ATF2 BPM system processing/control
• Bring spectrometer work to a reasonable
  scientific conclusion over next three years
• Could even reconsider renaming WP9 Cavity Beam
  Position monitors
• More complete spectrometer tests impossible
  (dependent on funding)
• Future of ESA facility might be in doubt
• ATF2 work is important and a natural place for
  high precision BPM work
• More generally must rely on existing
  cavity/calibration/electronics/processing systems