14
In this mode the indicator operation is carried out to the following thresholds:
1)
The fixed
threshold by MED
, set up in the communication mode with the PC by the user-
administrator;
When the installed threshold is exceeded by MED the indicator sends light, sound and/or vibrating
signals. Being so single-tone periodical signals are sent with the constant interval and duration 1 s by making
it possible for the user to acknowledge indication when threshold by MED is exceeded from the operation
threshold.
2)
The gamma channel operation threshold
(the minimum detection level) calculated in the
calibration mode and taking into account the changes in the background level. When the gamma channel
threshold is exceeded the indicator light, sound and/or vibrating signals. Being so, frequency of the received
signals is constant and is increased along with the exceeded
gamma channel operation threshold
.
The whole range of energies of the indicator gamma radiations is divided into four energy channels.
Three channels correspond to areas of interest for low, middle and high energies, and the 4
th
one – to the
whole range of energies of the gamma radiation.
The operation threshold
is calculated for every channel.
The processor counts impulses every 0,25 s by each channel from the detection block, and it keeps
the amount of impulses during the counting. Being so, every 0,25 s the number of impulses over the last
(new) interval is added to the current amount, and the number of impulses during the first (the oldest)
interval is deducted from the sum of impulses (the current average). So, the number of impulses stored in the
processor for each channel is renewed every 0,25 s.
The current average number of impulses is compared every 0,25 s with
operation thresholds
for
each channel,
which are calculated in the calibration mode (clause 2.2.3)
. If the current average value of
the number of impulses by any channel exceeds the threshold value, indication (light, sound and/or
vibrating) is switched on.
3)
The operation threshold for the neutron channel
2
1
c
(The minimum detection level), calculated
in the calibration mode and taking into account the changes in the background level. If the operation
threshold is exceeded the indicator sends light, sound and/or vibrating signals. Being so, double signals are
sent with the permanent interval and duration, what making it possible for the user to find indication when
the operation threshold of gamma channel exceeds operation of the neutron channel.
In the searching mode the device resolves the problems of detection and localization of sources of
gamma and neutron radiation.
Detection of sources of gamma and neutron
2
radiation (II)
For II detection the device should be located so that the rear side (wherein the clamp is fixed) should
be directed to the tested object . The closer the device is placed to the tested object (luggage, a human being,
a container, a vehicle, etc) and the slower it travels along the object, detection efficiency is higher.
For II detection under conditions when sound signals of the indicator may be not heard (for example,
excessive noise) the vibrating and light indicator should be used.
One should remember that indicator sensitivity and frequency of false operations depend on:
- the preset value of n factor by the gamma channel
;
- the preset value of n factor by the neutron channel
;
- the background level calculated by the indicator in the calibration mode by the background level.
In case when automatic calibration is switched on in the communication mode with a PC, the
indicator will automatically take into account slow changes of the background level and calibrate by a new
background level approximately after every ten minutes with the reduction of the background level or after
somewhat bigger intervals during increase of the background level. However, automatic calibration will be
carried out under conditions of absence of indicator operations or sharp changes of the background level
over certain intervals defined by the algorithm.
2
РМ
1703GNO,
РМ
1703GNA,
РМ
1703GNB