Transcript Triggering and Measurement Devices for the LCLS Undulator Test

Triggering and Measurement Devices
for the LCLS Undulator Test Bench
Kirsten Hacker
October 14, 2004
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
A basic triggering setup
Linear scale
with
encoder read
head
10/14/04
TTL
Quadrature Signal
every 1 um for 3 m
3,000,000 edges
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Triggering and Measurement Devices for LCLS Undulator…
Trigger
Generation
Every ~
100th edge
Kirsten Hacker
[email protected]
Device
With <
40,000
Memory
locations
Triggering problems
Carriage pitch and yaw => if you trigger on
every nth edge, you will generate triggering
errors
1um
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Triggering problems
Carriage pitch and yaw => if you trigger on
every nth edge, you will generate triggering
errors
1um
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Single triggers for specified positions
over a specified distance
Position change
Direction
Record of triggered
positions
Use index pulses on linear
scale to start and stop
trigger generation
A
B
Z
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
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
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
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
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
FPGA benefits
Easy to change and expand (x,y,z,…)
Easy to interface with process control
software
Programmed with LabView (quick learning
curve)
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Executes in parallel
Checks for change in digital signal at > 40
MHz
Compares input digital status to previous
loop iteration’s digital status
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
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
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
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
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Test setup
TTL
Quadrature Signal
every 1 um for 3 m
3,000,000 edges
FPGA module
Programmed
With LabView
PXI Crate
Running
LabView
PC
Running
File-sharing
LabWindows
Process
control
Trigger
Measured
Signal
10/14/04
Device
With <
40,000
Memory
locations
GPIB
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
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
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Measurement System
10 meter cable
Hall Probe
HP3458
multimeter
Carriage
Synchronized
Voltage
Sampler
Capacitive Distance Sensor
Coil
A=0.2 m^2
Pre-amp
G=1000
+
-
10 meter cable
∫
FPGA
Triggers
HP3458
multimeter
Linear Scale Encoder
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Measurement System
10 meter cable
Hall Probe
HP3458
multimeter
Carriage
Synchronized
Voltage
Sampler
Capacitive Distance Sensor
Coil
A=1.2 m^2
Pre-amp
G=1000
+
10 meter cable
-
∫
FPGA
Triggers
HP3458
multimeter
Linear Scale Encoder
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Hall probe comparison
Sentron X
Sentron Y
Bell
Group 3
Specification from first field integral
1e^-5 T
Sentron AG 2MR48/3B (ANL)
Bell Series 9900
(DESY) with
aluminum probe
Group 3 - 141
with 141 probe
Group 3 – 151
with 141 probe
10/14/04
Measurements taken with
probes in zeroing chamber
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Coil measurements
10 meter BNC cable
Gain=1000
∫
voltmeter
Flux tolerance =
2e^-6 V*s
Gain=100
From the integrator
500 ohm ~
resistance of coil
∫
voltmeter
.2 m^2 ~
area of coil
Field Tolerance = 1e^-5 T
Better to send milli-Volt
over 10 m cable than a
micro-Volt
Better to integrate a milliVolt than a micro-Volt
10/14/04
Flux = Field * Area = 2e^-6 V*s
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Pre-amp DC drift contribution
Integrator +
10 m cable +
Ectron 560
Pre-amp+
500 Ohm
resistor
LS480
Integrator+
10 m cable +
500 Ohm
resistor
10/14/04
Tolerance=2e^-6 V*s
Scale corrected for gain
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]
Progress
LabView FPGA triggering
Hall Probe comparisons
Ectron pre-amp + LS480 Fluxmeter
10/14/04
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Triggering and Measurement Devices for LCLS Undulator…
Kirsten Hacker
[email protected]