Rise Time
Sets the rise time of the trapezoidal filter.
Note
Having the ability to independently set the Rise Time and Flat Top allows
greater flexibility when optimizing the processing time or shaping for a wide
variety of detector applications. Additional information on adjustments is of
-
fered in Appendix C of this manual.
Flat Top
Sets the length of time for the trapezoid filter flat top.
Note
Independent adjustment of the flat top allows the shaping function to be op
-
timized for detectors with long charge collection time, without a large in
-
crease in the overall processing time. Additional information on these
adjustments is offered in Appendix C of this manual.
Pole/Zero
When operating with preamplifiers using RC feedback, the signal that is processed is
normally a tail pulse with a fast rise time and longer exponential fall time. The fall
time constant, or pole, is typically 50 µsec or greater. The long tail (pole) is normally
removed prior to digitizing and filtering the signal. Removal of the tail time constant is
accomplished by the insertion of another time constant (zero) which compensates for
the pole of the input signal. This is set using the Pole Zero parameter.
Note The information of interest for the spectroscopic measurement is contained
within the rise time of the signal. Removal of the tail pulse, or pole, does not
affect your acquisition.
The filter's Pole/Zero control allows you to manually adjust the pole/zero setting
while monitoring the filter output with an external oscilloscope or digital oscilloscope.
The slidebar control offers a variable range from 0 to 4095 units, which correlates to a
compensation in the range of approximately 40 µsec to infinity.
The Lynx' built-in digital oscilloscope (DSO) can be used as an aid to verify proper
automatic or manual pole zero compensation by observing that the energy signal re
-
turns to the baseline with no under or overshoot.
Auto Pole Zero
The automatic pole zero sequence is a manually-operated automatic routine to adjust
the Pole/Zero setting (see above). Automatic Pole Zero requires a number of valid nu
-
clear events to be processed in order to successfully complete within a three-minute
time period.
Chapter 4 - Web-based Operation Filter
84 Lynx™ Digital Signal Analyzer
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