Fluke Biomedical TNT 12000 User Manual
Page 107
Model 96035B Ion Chamber
Calibration and Verification
B
B-5
Table B-1. Specifications for PTB Defined Unattenuated Beam Qualities
PTB
Denomination
kVp
Added Filtration
in mm AI
First HVL in mm
AI
First HVL in mm
Cu
DN30 30
2.5 1.05
0.031
DN40 40
2.5 1.42
0.045
DN50 50
2.5 1.82
0.059
DN70 70
2.5 2.45
0.081
DN90 90
2.5 3.10
0.112
DN100 100
2.5 3.60
0.126
DN120 120
2.5 4.30
0.165
DN150 150
2.5 5.40
0.231
DN30 30
2.5 1.05
0.031
Typical energy correction factor curves are obtained by dividing the calibration factor at
each beam quality by the calibration factor at a reference point and plotting the result
versus first HVL. L100 is chosen as the reference point for chambers receiving the
standard calibration while DV70 is chosen for chambers receiving the PTB calibration
option.
The energy correction factors are multiplicative, such that multiplying the measured ion
chamber output at any beam quality by the appropriate value from the curve will correct
readings not made at the calibration factor beam quality.
The typical correction factor curves for the unattenuated beam are shown below
normalized to L100 in Figure B-3 and DV70 in Figure B-4.
Typical Correction Factors - Diagnostic Unattenuated Beam
Normalized to L100
First HVL (mm A1)
Colrrection Factor
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
1.08
1.06
1.04
1.02
1
0.98
0.96
0.94
0.92
40
30
50
70
120
150
90
100
fct39.eps
Figure B-3. Energy Correction Factors for Model 96035C in Unattenuated Beam Normalized to L100