1. Steps Towards Beam Commissioning: BPM System
Boris Keil :: For The GFA/ABK Diagnostics Section :: Paul Scherrer Institut
Steps Towards Beam Commissioning: BPM System
SwissFEL Commissioning Workshop, March 21-22, 2016
FHNW Campus Brugg-Windisch

2. Our System (Phase 1, Excl. Athos ...)
BPM Pickups & Mechanical Supports (AMI Collaboration)
7 CBPM38
111 CBPM16
27 CBPM8 (undulators)
BPM Hardware
75 BPM crates (MBUs = customized temp. stabilized low-noise crate)
75 FPGA boards with ADC mezzanines (+ 57 boards for other diag. systems)
118 RF front-ends 3.3GHz (CBPM16/38)
27 RF front-ends 4.9GHz (CBPM8)
11 FPGA boards (in 7 VME crates), connected to the MBUs via fiber optics,
for access to MBUs via VMEbus (from IFC1210 EPICS VME IOCs).
Firmware/Software
FPGA firmware & embedded software (incl. timing receiver on BPM FPGA board)
(large parts re-used for other diagnostics systems)
Control system interface (D. Zimoch's generic driver) + EPICS records
Long-term: BS DAQ streaming directly from BPM FPGA board (Ethernet)
Injector: 33 BPMs (CBPM38/16), 17 MBUs.

3. Our System (Phase 1, Excl. Athos ...)
CBPM38
CBPM16
CBPM8
BPM Electronics

4. Our Most Important Interfaces To (Dependencies On) Other Expert Groups
Interfaces / Dependencies
AMI & alignment group (pickup design & alignment)
Vacuum group / SwissFEL project team (pickup installation coordination)
Controls group
EPICS integration
Archiving / BS-DAQ
Timing system interface (BPM FPGA board decodes timing protocol directly -> no extra timing board needed)
AIT (maintenance interface of BPM FPGA boards connected to AIT Ethernet switches)
Cabling group
Operations (commissioning/operation support)
Beam dynamics (commissioning support)
...

5. Steps Towards Beam Commissioning/Operation: Hardware Installation
BPM Pickup Status
CBPM16 & CBPM38 production finished, pickups ready & being installed
CBPM8 pickups in production, ready for installation 8/2016 -> schedule
tight but still O.K.
BPM Electronics Status
BPM electronics in production, ready for injector installation 4/2016, for whole machine 8/2016 -> schedule tight but still O.K.
BPM Software/Firmware Status
FPGA firmware/software: Will be ready 4/2016
Control system interface: Will be ready 4/2016
Timing system interface (of BPM FPGA board): Tested & O.K.

6. Steps Towards Beam Commissioning/Operation: System commissioning In OSFA Before Beam
BPM Pickups
Pickup components all tested before assembly, again after brazing/welding (RF properties with NWA, vacuum leak test, ...), to be tested again after installation in tunnel incl. cables (via NWA).
CBPM16/38 tests done except post-installation test (next months)
Last CBPM8 tests 8-9/2016.
BPM Electronics
Full test & pre-calibration in lab with signal generator that simulates beam signal.
BPM Software/Firmware
FPGA firmware/software: Test in lab with electronics
Controls interface:
EPICS records: Tested in WLHA (slightly different records & memory map) with MVME IOCs, tested recently again with IFC1210 IOCs -> O.K. now.
Archiver & BS DAQ: To be tested when ready. For BPM commissioning at 10Hz, Archiver a la SITF would be O.K., for 100Hz user operation we need more.
Timing interface: Tested in lab with pre-series timing system -> O.K.

7. Steps Towards Beam Commissioning/Operation: Handover To Operation, Pre-Beam Checks
Pre-Beam Checks were discussed on the previous slide
"Hand-over to operation" (General Comments ...)
Systems are often commissioned and maintained by expert groups and not "handed over" to operations.
Of course there must be an agreement with operations:
What functionality will be available when (+ task distribution)
Which tasks are taken over by experts (for how long after 1st beam: days, weeks, months, years, forever), and which tasks are immediately or gradually taken over by operators (including people from expert groups working part or full time as operators for a while).
Experts need experience with systems (calibration, exceptions, ...) before gradually teaching operators to take over some tasks initially done by experts.

8. Steps Towards Beam Commissioning/Operation: BPM Functionality & Performance
"BPM Functionality & 1st Beam"
Measurement of position & charge (incl. "valid" flags) with nominal resolution and drift (CBPM38: <10um, CBPM16: <5um, CBPM8: <1um)
Limitations:
CBPM38/16 need stable arrival time (first SITF beam: sometimes ns-scale gun timing jumps), otherwise resolution will be much worse. CBPM8 uncritical.
Scaling factors (position, charge) ~10% error (need beam based calibration)
Jumps (position, charge) when attenuators are switched (~1% of measured value)
Position resolution close to 0mm suboptimal (pickup angle misalignment)
10Hz operation (low-level: 100Hz, IOC & archiving: 10Hz)
Final Functionality & Performance
More robust against large arrival time jitter (more complex signal processing)
No position/charge jumps when attenuators are switched (beam based cal.)
Improved resolution near 0mm offset (beam based pickup angle alignment)
100Hz / 2 bunch operation

9. Steps Towards Beam Commissioning/Operation: System Commissioning With Beam
BPM Pickups
Position offset (X & Y) and beam angle (dX/dS, dY/dS) need to be measured with beam, then each pickup must be realigned (manually, by someone in the tunnel) to reach optimal performance.
BPM Electronics
Has systematic measurement errors (e.g. nonlinearities, deviations of nominal and actual attenuator settings, etc.) that must be calibrated out with beam to reach optimal performance (# calibration parameters ~1000+ !)
Overall BPM System
Scaling factor for BPMs will be estimated pre-beam (maybe ~10%), should then be verified and fine-tuned with beam using screens, wire scanners etc.
Expected time for commissioning & calibration:
Basic commissioning: 15 min./BPM dedicated, 15 min./BPM parasitic
-> 8+8 hours (1+1 shift) for injector, hours (4+4 shifts) for linac, T&U.
Extended commissioning (optimization): min./BPM (dedic./parasitic)
(2+2 shifts injector, 8+8 shifts linac, T&U).
Basic: First weeks, extended: First months of beam operation.

10. What Makes Us Confident And Happy
BPM systems development & production so far going smoothly (minor issues were solved, e.g. production company delays)
Schedule tight but still O.K.
Good collaboration with other expert groups

11. What Makes Us Worry (Regarding BPMs)
Controls doing great job but have limited personnel resources ...
Control System
We need to record & store BPM data at bunch rep rate (continuously for hours, days, weeks). For 10Hz & first months of commissioning, a SITF style archiver is O.K. For 100Hz, we do not yet know when a mature solution is available and what performance (records/s, MByte/s per BPM) we can expect.
Performance of standard VME IOC (IFC1210) O.K. for first commissioning at 10Hz, but – on longer timescales - more performance is desirable (CPU performance, BS DAQ bandwidth, ...). Possible solutions: 1) BS DAQ streaming directly from BPM electronics 2) Using more performant IOCs (e.g. PCs).

12. What Makes Us Worry (In General ...)
SITF
Most relevant results obtained much later than originally planned.
First years: Tried to do "beam development" (trying to obtain results), rather than (more) "machine development" (getting the machine ready to obtain these results efficiently).
SwissFEL
Much more components & newly designed systems (often not tested at SITF after its early shutdown ...) -> much higher risks & less time for commissioning.
User facility, not test facility: Much higher requirements (MTBF, stability, ...), but little safety margins (compared to E-XFEL, LCLS, ...).
Different priorities?
Focus on "machine development", not "beam development"
Focus on aiding all expert groups to reach a performance, reproducibility and MTBF for their subsystems (and resulting beam parameters) needed for a stable FEL user facility.
See expert groups as (integral) part of "the commissioning team": Commissioning is not just control room shifts, but also (sometimes mainly) work on subsystems , data analysis by experts outside the control room, etc.

13. Wir schaffen Wissen – heute für morgen
Thanks to all PSI expert
groups & SwissFEL PM for
their support.