932502G / 0618
APPENDIX D. CALCULATIONS
D.2. Gain and Zero Stabilization
The gain stabilizer requires a peak in the spectrum to monitor the changes in the gain of the
system amplifier. The gain stabilizer controls the amplification factor of a separate amplifier so
that the peak will be maintained in its original position.
The zero stabilizer enables you to control the zero-level (or offset) stabilizer. The zero-level
stabilizer uses a peak in the spectrum to monitor the changes in the zero level of the system
amplifier. The zero stabilizer controls the offset bias level so the peak will be maintained in its
original position.
For both functions, the input pulse-height-to-channel-number relationship is:
where:
Intercept
= The channel number of the zero-height input pulse
Gain
= The relation between pulse height and channel number (slope of the curve)
Changes in either the intercept or gain can affect the positions of all the peaks in the spectrum.
When used with the zero stabilizer, both the zero intercept and the gain (slope) will be monitored
to keep all the peaks in the spectrum stabilized. The zero stabilization and gain stabilization are
separate functions in the DSPEC 50 but both will affect the position of the peaks in the
spectrum.
The stabilization operates by keeping a peak centered in an ROI you have defined. The ROI
should be made symmetrically about the center of a peak with reasonably good count rate in the
higher channels of the spectrum. The ROI should be about twice the FWHM of the peak. If the
region is too large, counts not in the peak will have an effect on the stabilization.
Before setting either stabilization peak, the coarse and fine gains should be set to the desired
values, and optimization or pole zero performed.
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