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Technical Description - Physics
Automatic Calculation of
Calibration Monitoring
Time
6-10
SAM12 User Manual
Residual Contamination is assumed to exist where the
following formula is satisfied:
(
)
−
≥
C
B
N
sum
RCC
RCC
where
C
is the average count rate during the Residual Contamination
RCC
Count period.
N
is the RCC threshold variable (see
RCC
The default setting for N
less that the sum of the probabilities of detection and false alarm (
P+F).
In the event of residual contamination being detected, the SAM
will enter an "Out of Service" state and monitoring will not be
possible (see
Notes regarding Residual Contamination Check
(page
5-60)). The doors will lock if the option is fitted.
Intervention by a password holder will be required to terminate
the fault status (see
Instrument Contaminated (page
The Calibration technique (see
uses flash (10 second) background and source counts to
automatically calculate the count time for the user. The
Calibration Accuracy and the associated confidence level is set
in Params 3 menu (see
The count confidence level has a default setting of 3σ (99.7%)
which is a generally accepted Confidence level that produces
acceptable count times.
Then Calibration Count Time,
where
N
= 3 (Count Confidence Level of 99.7%)
conf
n = Flash source + background Count (cps)
b = Flash Background Count (cps)
A = Calibration Accuracy (ratio e.g. 5% = 0.05)
The calculated count time is rounded up to the nearest whole
second and T is limited to 10,000 seconds.
(
)
+
(
n
nb
=
2
T
N
(
)
−
2
conf
2
A
n
b
the CCM channel and all the detectors are calibrated at the
same time. This may lead to slightly extended counting times
due to the lower CCM channel efficiency.
Isotope gamma efficiencies
The following data were obtained during type testing in a stable
7-10 μR/h (0.07-0.1 μSv/h) Background using pant-sources in
⎛
⎞
B
⎜ ⎜
⎟ ⎟
sum
⎝
⎠
T
MON
is 7.0σ and should never be set to a
RCC
Calibration Menu (page
Params 3 (page
5-11)).
Note that when CCM (see
)
Menu (page
5-30)) is installed,
'
Sec
s
60
during a
Co calibration, both
Issue: 1.0
Params 1 (page
5-8)).
5-61)).
5-19))
CCM
Thermo Fisher Scientific
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