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Triggering and Measurement Devices for the LCLS Undulator Test Bench

Triggering and Measurement Devices for the LCLS Undulator Test Bench. Kirsten Hacker October 14, 2004. Quadrature Signal. TTL. every 1 um for 3 m 3,000,000 edges. A basic triggering setup. Linear scale with encoder read head. Trigger Generation Every ~ 100 th edge. Device With <

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Triggering and Measurement Devices for the LCLS Undulator Test Bench

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  1. Triggering and Measurement Devicesfor the LCLS Undulator Test Bench Kirsten Hacker October 14, 2004

  2. Quadrature Signal TTL every 1 um for 3 m 3,000,000 edges A basic triggering setup Linear scale with encoder read head Trigger Generation Every ~ 100th edge Device With < 40,000 Memory locations

  3. Triggering problems • Carriage pitch and yaw => if you trigger on every nth edge, you will generate triggering errors 1um

  4. Triggering problems • Carriage pitch and yaw => if you trigger on every nth edge, you will generate triggering errors 1um

  5. A B Z Single triggers for specified positionsover a specified distance • Position change • Direction • Record of triggered positions • Use index pulses on linear scale to start and stop trigger generation

  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. 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. FPGA benefits • Easy to change and expand (x,y,z,…) • Easy to interface with process control software • Programmed with LabView (quick learning curve)

  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. 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. 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. Quadrature Signal TTL every 1 um for 3 m 3,000,000 edges Measured Signal Test setup FPGA module Programmed With LabView PXI Crate Running LabView PC Running LabWindows Process control File-sharing Trigger Device With < 40,000 Memory locations GPIB

  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. + - Measurement System Hall Probe 10 meter cable HP3458 multimeter Carriage FPGA Triggers Synchronized Voltage Sampler Capacitive Distance Sensor Pre-amp G=1000 Coil A=0.2 m^2 10 meter cable HP3458 multimeter ∫ Linear Scale Encoder

  15. Measurement System Hall Probe 10 meter cable HP3458 multimeter Carriage FPGA Triggers Synchronized Voltage Sampler Capacitive Distance Sensor Pre-amp G=1000 Coil A=1.2 m^2 + 10 meter cable ∫ HP3458 multimeter - Linear Scale Encoder

  16. Sentron X Sentron Y Bell Group 3 Hall probe comparison • 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 Specification from first field integral 1e^-5 T Measurements taken with probes in zeroing chamber

  17. ∫ ∫ Coil measurements 10 meter BNC cable voltmeter • Better to send milli-Volt over 10 m cable than a micro-Volt • Better to integrate a milli-Volt than a micro-Volt Flux tolerance = 2e^-6 V*s From the integrator Gain=1000 Gain=100 voltmeter 500 ohm ~ resistance of coil .2 m^2 ~ area of coil Field Tolerance = 1e^-5 T Flux = Field * Area = 2e^-6 V*s

  18. Pre-amp DC drift contribution Integrator + 10 m cable + Ectron 560 Pre-amp+ 500 Ohm resistor LS480 Integrator+ 10 m cable + 500 Ohm resistor Tolerance=2e^-6 V*s Scale corrected for gain

  19. Progress • LabView FPGA triggering • Hall Probe comparisons • Ectron pre-amp + LS480 Fluxmeter

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