1. Beam position monitors LCABD Plenary meeting Bristol, 24th March 2009 A. Aryshev, S. T. Boogert, G. Boorman, S. Molloy, N. Joshi JAI at Royal Holloway A. Lyapin University College London

2. 2 Outline Commissioning ATF2 beam line (corner stone of next 2 years work) Software systems 40+ high performance BPMs S-Band BPM electronics Just completed electronics installation Commissioning in April 2009 Diamond BPM work Low cost high precision BPM for light sources CLIC drive beam RF diagnostics

3. 3 Spectrometry Key knowledge from spectrometer tests Stability of BPM systems most important ESA test beam problems with BPM stability on time scales ~12 hours Beam stabilisation at ATF2 requires 50 nm for time scales ~ 1 operation week, 120 hours ATF2 design goals same for energy spectrometer Environmental monitoring Thermal Low level RF systems (locking, calibration signals)

4. 4 ATF2 beam line (BPM centric) Last dipole of EXT FF S-band system C-band system

5. 5 Example ATF2 Quad/BPM/Mover package C-band cavity integrated into quad Calibration by moving quad and BPM Mixer electronics Quad support Quad Quad mover C-band BPM

6. 6 ATF2 beam line commissioning Challenging task 37 dipole cavities 33 C-band (small aperture, normal beam transport applications) Based on experience and designs of LCABD 4 S-band (large aperture, FF large beta function) Closely linked to energy spectrometer design 5 reference cavities 4 C-band 1 S-band

7. 7 BPM processing software Real time processing of mixed cavity output signals Convert amplitude and phase of signal to position for the ATF2 control system Required for Orbit control (Beam based alignment etc) Dispersion and coupling correction Beam orbit for other experiments (Interaction point beam size monitor, laser-wire) EPICS based soft input output (IOC) controller system Simple to use for large, novice user group

8. 8 BPM processing algorithms Mix RF with local oscillator Always obtain IF at ~20 MHz Filter 2w frequency (gaussian filter) Identify point to measure amplitude and phase Calculate In-phase and quadrature components 20 MHz IF is further mixed digitally to baseband 88 Channels of 120 MHz digitizers Digital mixing, filtering and calibration Transmit to ATF2 control system

9. 9 Software design Complete robust EPICS design No crashes since December 2008 Multiple user control and diagnostics system

10. 10 BPM control and readout software

11. 11 Tuning cavity readout

12. 12 Tuning cavity readout

13. 13 Calibration of BPMs Typical calibration over +- 100 micron Move BPM/Quad package (also kick beam) Clear IQ rotation Position dependence Currently signals have 20 dB attenuation Jitter dominated by beam jitter

14. 14 Trigger/phase problems Low level RF and trigger distribution at ATF quite obfuscated race conditions phase drifts Result large position shifts Must resolve in order to have stable system

15. 15 Dynamic range example Example large distance calibration +-1mm IQ rotation clear BPM response very linear Some x-y coupling at large x

16. 16 S-band system S-band electronics complete (LCABD responsibility) Reference cavity (being delivered next week)

17. 17 Future work Developing three major strands to post-LCABD work RF diagnostics for future light sources Beam position monitors (beam alignment w.r.t. undulators) Installation at Diamond light source (3 C-band cavities + 1 reference) CLIC drive beam BPMs and RF phase detection Industrialised BPM systems Collaboration developing with FMB-Oxford

18. 18 Diamond BPM system Use already proven technology Turn key operation is being developed at KEK Develop BPM for FEL based light sources. C-band system >>> Booster-Diamond transfer line

19. 19 Future BPM work (AL, TIPP09 conf) Thinking about future design Continue lineage of current designs (single slot, is example)

20. 20 Summary ATF2 seen significant progress Complete installation of final focus system Calibration and operation of C-band system Near turn key RF cavity BPM processing system Complete software implementation Started new projects on advanced BPM systems Is LCABD correct avenue to discuss general continuation of diagnostics work Energy spectrometry developed into package for BDS BPMs as well as specialist systems