ORTEC DSPEC Pro, Hardware User Manual

Page: 42 / 108

DSPEC Pro
®
Digital Gamma-Ray Spectrometer User’s Manual 794380D / 0914
32
Turning on this feature automatically sets the minimum protection time (highest throughput rate)
based on your current Rise Time and Flattop settings, however, you can adjust this value at any
time. Each time you change the rise time or flattop, the DSPEC Pro will automatically set itself
to the new minimum protection time.
2.3.3.1. “Training” the Resolution Enhancer
The Resolution Enhancer can help reduce the low-side peak tailing that results from increased
charge trapping; see the discussion in Section 1.3. It operates by measuring the rise time (collec-
tion time) of the pulses and adjusting the gain based on the rise time. This is done on each pulse.
The gain adjustment value for the rise time is stored in a table. The values in the table must be
set by “training” the Resolution Enhancer. Training requires two to four 15-minute data acqui-
sitions with a mixed-gamma source, for instance, mixed gamma with
241
Am. The source should
have sufficient activity that the detector registers a count rate of 5000 cps on the endcap.
Marking the Resolution Enhancer checkbox enables/disables the “learning” mode. Once
trained, the enhancer continues to operate until disabled as discussed on page 33.
NOTE This feature typically improves the shape of low-energy peaks moreso than high-
energy peaks, and does not improve poor resolution due to causes other than charge
trapping.
To Enable and Train the Enhancer
Note that this procedure requires detector recalibration.
1) Right-click in the spectrum window and turn on the Input Count Rate option.
2) Set the desired bias and gain, position the source to deliver a count rate of 1000–5000 cps,
and start the Optimize routine. A message at the bottom of the Amplifier tab will indicate
whether the count rate is too high or low. At the optimum count rate, optimization should
take less than 5 minutes.
2) Issue the Clear command, position the source on or near the endcap, set a Real Time preset
of 1000 seconds, and acquire a spectrum.
3) Energy calibrate on the lowest and highest peaks (for instance, the
241
Am 59.54 keV and
60
Co
1332.51 keV gamma rays); use the Peak Info command to obtain the FWHM data for the
241
Am,
109
Cd,
137
Cs, and
60
Co peaks; mark the
137
Cs 661.62 keV peak as an ROI; and save the
spectrum with a name (and optional sample description) indicating the MCB has been auto-
optimized.