Berthold LB 134, User Manual

Page: 131 / 157

LB 134 9. Basis of Calculation
121
A
R R
Bgrd Source
Detection



(1) (A in Bq)
W
N
Detection
CAL



1
(2)
 
Bgrd Sample CAL Surface
R R N A
   (3)
W
R R
A
Detection
Bgrd Sample
Surface




(4)
The ISO calibration is performed according to the International
Standard ISO 7503-1 [1] relative to the surface emission rate
q
2

of the reference source and the sensitive detector surface
W, as a reference surface. In accordance with ISO 7503-1, the
equations 5-8 also take into account the emission efficiency

Source
.


2
q
R R
Bgrd Source
Detection


(5)
source Detection
CAL
W
N
 
 

1
(6)
 
Bgrd Sample CAL Surface
R R N A
   (7)
source Detection
Bgrd Sample
Surface
W
R R
A
   


(8) (Bq/cm²)
In this formula the area W is explicitly included, therefore use
for the emission rate q
2
π
the total number of betas per second.
If the surface emission rate is not available, as in this case, we
use
2
2
A
q


The emitter efficiency

source
of alpha emitters must be assumed
to be 0.25, that of beta emitters 0.50 [1]. For some beta emitters
with low beta energies we also have to use 0.25. If the sensitive
detector area is larger than 300 cm
2
, 300 cm
2
is used for W.
[1] DIN ISO 7503-1:1990-07: Evaluation of surface contamina-
tion; beta-emitters (maximum beta energy greater than
0,15 MeV) and alpha-emitters; identical with ISO 7503-
1:1988