GBS Elektronik MCA166-USB Behavior at different Temperatures - Manual (Page 7)

N
keV cps
keV
opt
s
=
∗
∗ ∗ ⋅





 =
−
22 1400
2 186 1 6 10
30000
5 1
2
3
.
The stabilization cycle time is here 21s and the expected peak broadening is neglible (0.6%).
The default value for stabilization cycle area of 25000 seems to be rather at the upper end of useful values.
Especially with low count rate applications, it is very much recommended to use a newer version of WinSpec and
decrease the stabilization area value.
7. Linearity and accuracy of gain setting
In the scope of this study, also the absolute accuracy of the gain setting was investigated (Do not mix this with
the linearity of the ADC!). This measurement was also done with the MCA166 #141 and a GL1015R detector.
The absolute value of the scale / gain ratio depends severely on detector type and preamplifier. Even the
variations between several detectors of the same type may be large. E.g. the typical variation of signal amplitude
for CZT500 detectors from Ritec is about 20% [2]. Compared with that, the gain variation of different MCA166
units (typical 2-3%) can be neglected.
1 0 1 0 0
G ain s ettin g
1
10
C
h
a
n
n
e
ls
/k
e
V
Fig. 8. gain setting vs. energy scale using a GL1015 planar HPGe detector
1 0 1 0 0
G a in
0 .1 1 6
0 .1 2
0.1 2 4
0 .1 2 8
S
c
a
le
/G
a
in
r
a
ti
o
(
c
h
a
n
n
e
ls
/k
e
V
/g
a
in
)
Fig. 9. variation of the scale / gain ratio in dependence of the gain setting. The absolute gain setting is correct
within +/- 3%.
The nonlinearity of the gain shows the same oscillating behavior as the temperature drift coefficient, which shows
that the most critical component here is the adjustable gain amplifier.