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 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 Dipole LCABD BPMs Old SLAC BPMs

5. Cavity construction 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) Dipole cavity Reference cavity

6. ATF2 (Cavity BPMs) 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! C-band ATF2 cavity ~20 cavities 50 nm resolution Main beam steering/alignment diagnostic

7. Turn key diagnostic 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 Cavity (2.8 GHz) Mixer (IF ~20MHz) I-Q. position/tilt 100MHz digitiser 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 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 AI AO FPGA Multi-bunch data from nanoBPM

10. Integration with laserwire systems Beam position jitter might ruin laserwire system measurements –1 micron electron beam size –Subtract beam jitter requires <100nm 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