Radiation Therapy
Farmer-Type Ionization
Chamber, 0.6 cm
3
, Waterproof
Model 30-351
•
Completely waterproof, does not
require protective sleeve
•
Can be safely used in water
phantoms and solid state
phantoms
•
Open volume, vented at connector
•
Fully guarded up to the measuring
volume
•
Touchable parts free of high voltage
•
Extension cables up to 100 meters
in length are available
The waterproof 0.6 cm
3
ionization chamber (Model 30-351) is designed for absolute
dosimetry in radiation therapy. Since the chamber is waterproof, it may be used in water
phantoms and does not require a protective sleeve. It is rugged in construction and has
a PMMA/graphite thimble and an aluminum electrode. This chamber includes a
3.3 ft (1 m) cable, BNC Triax connector, and a PMMA buildup cap.
Specifications
Volume
0.6 cm
3
Response
2 • 10
-8
C/Gy
Leakage
± 4 10
-15
A
Polarizing voltage
Maximum 500 V
Cable length
3.3 ft (1 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), 1.85 gm/cm
3
(C)
Wall thickness
0.335 mm PMMA, 0.09 mm C
Area density
56.5 mg/cm
2
Electrode
Aluminum, 1.1 mm Ø, 21.2 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:
0.18 ms
400 V:
0.14 ms
500 V:
0.11 ms
Saturation behavior
Saturation
behavior
Polarizing
voltage
99.0%
saturation
99.5%
saturation
Maximum dose rate at
continuous irradiation
300 V
5.70 Gy/s
2.80 Gy/s
400 V
10.00 Gy/s
5.00 Gy/s
500 V
16.00 Gy/s
7.80 Gy/s
300 V
0.69 mGy
0.34 mGy
Maximum dose rate
per irradiation pulse
400 V
0.91 mGy
0.46 mGy
500 V
1.14 mGy
0.57 mGy
See next page for more specifications.
Specifications
(continued)
Diagram
23.6
21.2
Thimble
Ø 1 .1
Approximate dimensions in mm.
Drawing not to scale.
Ø 6 .1
Ø 6 .9 5
13
25.9
132.6
Buildup cap, PMMA
4.7
Ø 16.4
93.9
Energy dependence
1.05
1.03
Abs orbed dos e to water
Ai r k e r m a
1.01
1.00
1.00
1.00
1.00
1.00
40
60
100
150
Co-60
0.98
0.97
0.97
0.97
0.95
Photon Energy, kV
Directional dependence
90º
0º
180º
Reading / Dose, %
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
70 kV 20 48 69 81 88 99 100 100
98
96
91
88
70 kV
78
88
96 100 101 100 100 100 100 101 102 102
140 kV 36 66 82 90 94 100 100 100 100
98
96
94
140 kV
90
97 101 102 103 101 100 100
99
100 102 102
280 kV 57 80 90 94 96 100 100 100 100
99
98
97
280 kV
100 102 103 103 103 101 100 100 100 101 102 102
Co-60 67 85 91 95 97 100 100 100 100
99
99
98
Co-60
102 101 101 101 101 100 100 100 101 102 102 102
Optional accessories
Check Source,
90
Sr, 33 MBq (892 µCi) (Model 30-657)
Available model(s)
30-351
Farmer-Type Ionization Chamber, 0.6 cm
3
, Waterproof,
includes BNC Triax connector and PMMA buildup cap
Other types of triaxial cable connectors available
