1. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 1 Triggering and Measurement Devices for the LCLS Undulator Test Bench Kirsten Hacker October 14, 2004

2. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 2 A basic triggering setup Trigger Generation Every ~ 100 th edge Device With < 40,000 Memory locations Quadrature Signal TTL every 1 um for 3 m 3,000,000 edges Linear scale with encoder read head

3. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 3 Triggering problems Carriage pitch and yaw => if you trigger on every nth edge, you will generate triggering errors 1um

4. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 4 Triggering problems Carriage pitch and yaw => if you trigger on every nth edge, you will generate triggering errors 1um

5. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 5 A B Z Position change Direction Record of triggered positions Use index pulses on linear scale to start and stop trigger generation Single triggers for specified positions over a specified distance

6. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 6 Triggering solutions Design an electrical circuit to generate single triggers for specified positions Design software that executes on an FPGA to generate single triggers for specified positions (and record those positions) Joseph Xu, ANL

7. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 7 Triggering solutions Design an electrical circuit to generate single triggers for specified positions Design software that executes on an FPGA to generate single triggers for specified positions (and record those positions) Joseph Xu, ANL

8. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 8 FPGA benefits Easy to change and expand (x,y,z,…) Easy to interface with process control software Programmed with LabView (quick learning curve)

9. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 9 Executes in parallel Checks for change in digital signal at > 40 MHz Compares input digital status to previous loop iteration’s digital status

10. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 10 FPGA requirements Operates at more than 40 MHz so carriage must move slower than 10 m/s on a linear scale with micron resolution to avoid aliasing Encoder signal must have low electrical noise Noise spikes could be interpreted as position changes

11. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 11 Electrical noise reduction Use motor driver that doesn’t generate DC with chopping (special low-noise drive) Use low-noise power supply and minimize cable lengths for encoders Additional measures could include: Adding a Schmitt trigger Using a comparator with differential signals Using a line driver to reduce noise picked up on long cable

12. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 12 Test setup Quadrature Signal TTL every 1 um for 3 m 3,000,000 edges Device With < 40,000 Memory locations FPGA module Programmed With LabView PXI Crate Running LabView PC Running LabWindows Process control File-sharing Measured Signal Trigger GPIB

13. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 13 Successful triggering system tests Count lines on linear scale and get expected number Sample function generator input and get expected number of cycles Record every position for which a trigger was generated and write it to a file

14. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 14 Measurement System Hall Probe Coil A=0.2 m^2 HP3458 multimeter HP3458 multimeter + - FPGA Triggers Pre-amp G=1000 10 meter cable Capacitive Distance Sensor Synchronized Voltage Sampler Linear Scale Encoder ∫ Carriage

15. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 15 Measurement System Hall Probe Coil A=1.2 m^2 HP3458 multimeter HP3458 multimeter + - FPGA Triggers Pre-amp G=1000 10 meter cable Capacitive Distance Sensor Synchronized Voltage Sampler Linear Scale Encoder ∫ Carriage

16. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 16 Hall probe comparison Measurements taken with probes in zeroing chamber Sentron AG 2MR- 48/3B (ANL) Bell Series 9900 (DESY) with aluminum probe Group 3 - 141 with 141 probe Group 3 – 151 with 141 probe Sentron X Sentron Y Bell Group 3 Specification from first field integral 1e^-5 T

17. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 17 Coil measurements voltmeter Gain=1000 10 meter BNC cable 500 ohm ~ resistance of coil Field Tolerance = 1e^-5 T Flux = Field * Area = 2e^-6 V*s Flux tolerance = 2e^-6 V*s From the integrator ∫ ∫.2 m^2 ~ area of coil Better to send milli-Volt over 10 m cable than a micro-Volt Better to integrate a milli- Volt than a micro-Volt Gain=100

18. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 18 Pre-amp DC drift contribution LS480 Integrator+ 10 m cable + 500 Ohm resistor Integrator + 10 m cable + Ectron 560 Pre-amp+ 500 Ohm resistor Scale corrected for gain Tolerance=2e^-6 V*s

19. Kirsten Hacker Triggering and Measurement Devices for LCLS Undulator…keh@slac.stanford.edu 10/14/04 19 Progress LabView FPGA triggering Hall Probe comparisons Ectron pre-amp + LS480 Fluxmeter