Whole report - STUK

STUK-YTO-TR 175
5 SENSITIVITY TO HORIZONTAL
POSITIONING
The A 37
vs. horizontal distance to the CZT detector
of assembly #12350 (x-coordinate) is investigated
in Figure 11. The following linear curve was fitted
to the data:
A37 = y0
+ a* x, (1)
where y 0
and a are the curve parameters. The
slope a of the 137 Cs signal is about –10%/cm. Du-
ring the subsequent measurements the water gap
between an assembly and the entrance window of
the CZT detector was kept as constant as possible
(x = 0 cm). On the other hand, the Cs ratio seems
to be almost independent of the distance as shown
in Figure 11. The slope of the Cs ratio is
–0.0022(±0.0014) cm –1 . The measured raw data are
shown in Table A1.II in Annex 1.
420
0,20
137
Cs peak intensity (cps)
400
380
360
340
320
300
280
260
240
220
-5 -4 -3 -2 -1 0
x (cm)
0,15
0,10
0,05
0,00
134
Cs/
137
Cs activity ratio
Figure 11. Sensitivity of the gamma spectroscopic data to horizontal positioning. x=0 represents the
standard measurement distance. x=–4 cm is the position closest to the CZT detector. The circles represent
the 137 Cs signal, vertical scale on the left. The triangles display the 134 Cs/ 137 Cs activity ratio, vertical scale
on the right.
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