Background; Nbr (Natural Background Rejection) - Thermo Scientific RadEye SPRD Operating Instructions Manual

source. Please refer to chapter 1 for the detection of neutron
sources.
5.1

Background

During operation in count rate mode with sigma ≥ 2 the back-
ground radiation is always monitored and a smoothed, low-
pass filtered value is computed. This value, limited to 100 cps,
is used for the calculation of Alarm 1 if the sigma alarm is
activated. During sigma alarm the monitoring of background
is suspended.
On acknowledgement of an alarm 1, the background ratemeter is
set to the actual count rate and background learning continues.
5.2

NBR (natural background rejection)

For this additional feature the ratio between the detected
gamma energies is used to indicate unusual radiation condi-
tions. Three energy channels for low-, mid- and high range
energy are monitored and compared with three thresholds. If
the channels exceed the adjustable (via PC-program) thresh-
olds, an alarm is released and it appears a message "LOW
Ener." for low energy radiation, "MID Ener." for midrange
energy radiation respectively "HIGH Ener." for high energy
radiation, in the top line of the normal display. The alarm tone
and vibrator can be acknowledged by a short key depression.
The NBR-indicator can be activated by the menu function or
the PC-program RadEye.exe.
5-2 DB-100 E RadEye SPRD
Pi/Ff 04.11.2014