Radiation Therapy
Semiflex
™
Ionization Chamber,
0.125 cm
3
, Waterproof
Model 30-344
•
Suitable for use in water phantoms
or solid state phantoms
•
Measuring volume is fully vented
via the connector
•
Fully guarded up to measuring
volume
•
Touchable parts free of high voltage
•
Extension cables up to 100 meters
in length are available
The 0.125 cm
3
ionization chamber type (Model 30-344) is designed for measurements
in the useful beam of high energy photon and electron fields. The chamber is waterproof
and is used mainly for relative measurements in a water phantom or in an air scanner.
The measuring volume is approximately spherical resulting in a flat energy response
over an angle of 160º and a uniform spatial resolution, in all three axes, during
measurements in a phantom. The chamber includes a 4.3 ft (1.3 m) cable, BNC Triax
connector, PMMA buildup cap, and a short (36 mm) rigid stem for easy mounting.
Specifications
Volume
0.125 cm
3
Response
4 10
-9
C/Gy
Leakage
± 4 10
-15
A
Polarizing voltage
Maximum 500 V
Cable length
4.3 ft (1.3 m)
Cable leakage
10
-12
C/(Gy cm)
Wall material
PMMA (C
5
H
8
O
2
), Graphite (C)
Wall density
1.19 gm/cm
3
(PMMA), 0.82 gm/cm
3
(C)
Wall thickness
0.55 mm PMMA, 0.15 mm C
Area density
78 mg/cm
2
Electrode
Aluminum, 1.0 mm Ø, 5.0 mm long
Nominal useful range
30 keV to 50 MeV
Range of temperature
10º to 40ºC
Range of relative humidity
10% to 80%
Ion collection time
300 V:
0.14 ms
400 V:
0.10 ms
500 V:
0.08 ms
Saturation behavior
Saturation
behavior
Polarizing
voltage
99.0%
saturation
99.5%
saturation
Maximum dose rate at
continuous irradiation
300 V
5.6 Gy/s
2.8 Gy/s
400 V
10.0 Gy/s
5.0 Gy/s
500 V
15.0 Gy/s
7.5 Gy/s
300 V
0.7 mGy
0.4 mGy
Maximum dose rate
per irradiation pulse
400 V
1.0 mGy
0.5 mGy
500 V
1.2 mGy
0.6 mGy
See next page for more specifications.
Specifications
(continued)
Diagram
Approximate dimensions in mm.
Thimble
Buildup cap, PMMA
Energy dependence
1.10
Absorbed dose to water
Ai r k e r m a
1.05
1.00
1.00
0.97
0.96
0.97
1.00
0.95
0.96
0.96
0.97
0.90
60
100
150
Co-60
Photon Energy, kV
Directional dependence
90º
Reading / Dose, %
0º
180º
in Air
in PMMA
6º 12º 18º 24º 30º 60º 90º 120º 150º 162º 174º 180º
6º
12º 18º 24º 30º 60º 90º 120º 150º 162º 174º 180º
100 kV 3 20 44 67 80 97 100
99
96
95
94
93
100 kV
56
63
71
81
88
98 100 100 100 100 100 100
140 kV 10 32 55 76 87 99 100
99
97
97
96
96
140 kV
58
68
77
87
93
99 100 100 100 100 100 100
280 kV 33 62 78 87 93 99 100 101 101 101 100 100
280 kV
67
83
91
95
97
99 100 101 101 101 101 100
Co-60 79 89 93 95 97 100 100 100 100 100 100 100
Co-60
85
95
99 100 100 100 100 100 100 100 100 100
100 kV, 0.17 mm Cu HVL; 140 kV, 0.49 mm Cu HVL; 280 kV, 3,4 mm Cu HVL
Optional accessories
Check Source,
90
Sr, 33 MBq (892 µCi) (Model 30-657)
Available model(s)
30-344
Semiflex Ionization Chamber, 0.125 cm
3
, Waterproof,
includes BNC Triax connector, PMMA buildup cap, and 36 mm rigid
stem for mounting
Other types of triaxial cable connectors available
