True Coincidence Summing Correction in Gamma Spectroscopy

Temperature and Humidty
Humidity can have significant effects on the many cable connections that germanium
detection systems have.
• The change in moisture can affect cable connection impedance, which
ultimately can affect peak shape.
• The counting room should be maintained at 40-60 percent relative humidity.
There are two separate temperature effects that can be seen.
• The first deals with the detector itself. The band gap in the germanium crystal
is affected by the absolute temperature, so it is maintained at -196 ˚C using a
cryostat. The cryostats are designed to have minimum thermal leakage.
• The other temperature effect is that of the room environment on the
electronics. Although the detector and the electronics may be on a conditioned
line, the instability of temperature in the room can cause the pre-amplifier,
amplifier, and ADC/PHA portions of the system to respond erratically. The
temperature of the room should be maintained in the 21-27 ˚C range
1.5 Electronics for Gamma-Ray Spectrometry
The General Electronic System
The output from a gamma-ray detector is an amount of electrical charge proportional
to the amount of gamma-ray energy absorbed by the detector. The function of the
electronic system is to collect that charge, measure the amount and store the
information. A typical simple electronic system for gamma-ray spectroscopy is shown
in Figure-1.6.
Detector
Pre-
Amp
Linear
Amplifier
Analog to
Digital
Converter
Address
Scalar
(Crystal)
High
Voltage
Memory
Readout
Display
Figure 1.6 A simple schematic electronic system for gamma spectroscopy
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