Thermo Scientific SAM12, Руководство пользователя

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Technical Description - Physics Issue: 1.0
6-2 SAM12 User Manual Thermo Fisher Scientific
energy photons from cosmic radiation and consequently
improve MDA of selected radionuclide contaminants. In
addition, these discriminators may be used to identify the
presence of Naturally Occurring Radioactive Material
(NORM), using the Natural Background Reduction (NBR); and
60
Co using Cobalt Coincidence Monitoring (CCM). Thus any
article can be monitored accurately with known statistical
certainty often in a few seconds.
The article could be placed randomly anywhere inside the
measurement volume and not precisely in the geometric centre.
Additionally, a point source may be positioned anywhere on or
within the article itself. Therefore the sensitivity at the
extremities and uniformity of response throughout the
measurement volume, in all planes, are of interest. The
detectors are large, and arranged such that high sensitivity is
maintained throughout the measurement volume, almost perfect
4
π
coverage being attained by six detector variants (see Figure
1 (page 6-14) to Figure 10 (page 6-18) ).
A full type test report is available from Thermo Fisher
Scientific on request.
Explanation of the Operational Calculations
It is a requirement to measure contamination on personal
articles as quickly and accurately as possible. Optimum
detection efficiencies are required, with minimum statistical
error in giving alarm indications. Measurement of
contamination is dependent on ambient background level.
Accuracy of measurement of both background and
contamination is dependent on respective background and
contamination monitoring times, self absorption and also on
chosen probability of false alarm and probabilities of detection.
This section summarises the calculations employed by the CPU
in determining whether the parameters selected by the user
allow the monitor to operate correctly. The section then shows
the criteria used to determine whether an alarm has occurred
during a measuring sequence.
The parameters used in the calculations are summarised and
abbreviated as follows:
t
B
Background Update Time (seconds)
is the time
over which the average background counts have
been accumulated, this is a fixed 100 second rolling
average in the SAM. Background measurements
can only occur when the door is shut.
Spatial Response
Introduction
Description of Parameters
Used in Calculations