Fluke Biomedical TNT 12000 - Manual (Page 97)

Model 96020C Ion Chamber
Calibration and Verification
A
A-3
Average Intensity (mGy/s)
Average Intensity (R/min)
Collection Ef
ficiency
0.146
1 10 100 1000 10000
110%
100%
90%
80%
70%
60%
1.46 14.6 146 1460
Continuous
Half Wave
fct30.eps
Figure A-2. Collection Efficiency of the Model 96020C Ion Chamber
Air Density Correction ............................................. To perform air density corrections when using a calibration factor with
a reference temperature of 22 ° C, multiply the ion current by the
following correction factor, F:
F = (273.15 + T) / (295.15 x P)
Where T is the actual temperature in ° C and P is the pressure
expressed as a fraction of a standard atmosphere (1013 hPa). For
chambers with a calibration factor normalized to 20
° C, the
denominator is 293.15 x P.
Calibration and Verification
Calibration or calibration verification is performed by comparison of each 96020C ion
chamber with a reference chamber calibrated at either the National Institute of Standards
and Technology (NIST) or PTB.
Specifications for all PTB equivalent beam qualities are given in Table A-1 and Table A-
2 in the energy correction factor section.
Standard Calibration
The standard calibration is performed at the Fluke Biomedical, Radiation Management
Services equivalent of H60 (NIST defined as 60 kVp, first HVL of 6.0 mm Al,
homogeneity coefficient of 94). The calibration factor is normalized to 22 ° C and
1013 hPa of atmospheric pressure.
European Calibration Option
This calibration option replaces the standard calibration for units sold in Europe, or when
specifically requested by a customer. This calibration is performed at the Fluke
Biomedical, Radiation Management Services equivalent of DH70 (PTB defined as
70 kVp, first HVL of 6.77 mm Al). The calibration factor is normalized to 20 ° C and
1013 hPa of atmospheric pressure.
PTB Calibration Option
This calibration option replaces the standard calibration when PTB requirements must be
met, or when specifically requested by a customer. This option includes calibration at
both of the beam qualities listed below. Calibration factors are normalized to 20 ° C and
1013 hPa of atmospheric pressure.