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

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

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

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

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

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

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

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

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

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

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

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