DSPEC
®
Digital Gamma-Ray Spectrometer
1
Ron Jenkins, R.W. Gould, and Dale Gedcke,
Quantitative X-Ray Spectrometry
(New York: Marcel Dekker,
Inc.), 1981, pp 266–267.
2
Note that this performance is superior to that of typical analog systems for which the specification is 70 ppm/
C
(50 ppm for the amplifier in quadrature with 50 ppm for the ADC).
16
System Conversion Gain
The overall gain of the system is appropriate for use with all types of
Ge detectors.
Coaxial
“GEM” (P-type) and “GAMMA-X” (N-type).
Low Energy
“LO-AX” (low-energy coaxial), “GLP” (planar Ge), “IGLET” and “IGLET-
X” (ultra-thin window planar Ge), and SLP (SiLi).
Dead-Time Correction
Extended live-time correction according to Gedcke–Hale method.
1
Accuracy: area of reference peak changes
±3% from 0 to 50,000 counts/s.
Linearity
Integral Nonlinearity
<±0.025% over top 99.5% of spectrum, measured with a mixed
source (
55
Fe @ 5.9 keV to
88
Y @ 1836 keV).
Differential Nonlinearity
<±1% (measured with a BNC pulser and ramp generator).
Temperature Coefficient
Gain
<50 ppm/
C. [Typically 30 ppm/
C.]
2
Offset
<10 ppm/
C, referred to the input with a total gain greater than 50; rise and fall
times of 16 µs, and flattop of 1.2 µs. (Similar to analog 6-µs shaping.)
Overload Recovery
At maximum gain, recovers to within 2% of rated output from X1000
overload in 2.5 non-overloaded pulse widths (measured using the InSight Virtual Oscilloscope).
Pulse Pile-Up Rejector
Automatically set threshold. Pulse-pair resolution typically 500 ns.
Automatic Pole-Zero
Computer-controlled. Can be set automatically or manually.
LLD
Digital lower level discriminator set in channels. Hard cutoff of data in channels below
the LLD setting.
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