19
N o t e
Before spectrum accumulation: take reference spectrum from reference source under
the same conditions that will be applied when taking spectra from tested object. As a reference source
can be used sources such as OSGI-3-2
152
Eu,
228
Th activity from 50 to 100 kBq. To take the reference
spectrum: place a reference source as close as possible to the geometrical (effective) center of the
gamma detector, and do the following procedure. Take the reference source away from the BDG1
when the reference spectrum accumulation is over, and the spectrum is saved into BDG1 memory.
LCD will display average count rate of the registered photon radiation impulses.
Over the area of the display the measured value display of count rate is analogue scale that
shows the relative value of the measured count rates, Figure 6.7.
1)
2)
3)
Figure 6.7
Pink scale (Figure 6.7 (1)) means that average count rate of gamma channel is low "Low
Count Rate" (less than 200 cps). Low gamma channel load results in uncertain spectrum.
Green scale (Figure 6.7 (2)) means that average count rate of gamma channel corresponds to
optimal load (from 200 to 20000 cps). Optimal gamma channel load results in reliable and
undistorted spectrum.
Red scale (Figure 6.7 (3)) means that average count rate of gamma channel is too high "High
Count Rate" (more than 20000 cps). Too high gamma channel load results in distorted spectrum.
Move to BDG1 as close as necessary to the tested object so that the count rate by detection
unit is within 200-20000 cps and then press OK.
During spectrum accumulation the LCD will display a graph of accumulated spectra in
progress, and time (Figure 6.8 (1)) that passes from the accumulation start. Displayed spectrum is
renewed every 10 s.
1)
2)
Figure 6.8
