Radiation Therapy
Markus
™
Electron Ionization
Chamber, 0.055 cm
3
, Waterproof
Model 30-329
•
Suitable for use in solid state
phantoms and water phantoms
•
Vented measuring volume
•
Fully guarded up to measuring
volume
•
Touchable parts free of high voltage
•
Extension cables up to 100 meters
in length are available
The Markus chamber is the very first chamber specifically designed for electron
dosimetry. The chamber may be used for measurements in water phantoms or solid state
phantoms. A PMMA waterproofing cap, 0.87 mm thick (equivalent to 1 mm of water),
and an annulus, for solid state phantom measurements, are included. The chamber’s
small measuring volume makes it ideal for electron measurements when very high spatial
resolution is required. The diaphragm front allows measurements in the buildup region
of electron fields to a depth of virtually zero. Markus includes a 3.4 ft (1.05 m) cable
and BNC Triax connector.
Specifications
Volume
0.055 cm
3
Response
2 10
-9
C/Gy
Leakage
± 2 10
-16
A
Polarizing voltage
300 V recommended, 400 V maximum
Cable length
3.4 ft (1.05 m)
Cable leakage
3.5 10
-12
C/(Gy cm)
Wall material
Polyethylene CH
2
Membrane thickness
0.03 mm
Area thickness
2.5 mg/cm
2
Electrode
Acrylic, graphite coated, 5.3 mm Ø
Nominal useful range
2 to 45 MeV
Range of temperature
10º to 40ºC
Range of relative humidity
10% to 80%
Ion collection time
150 V:
0.20 ms
300 V:
0.09 ms
400 V:
0.07 ms
Saturation behavior
Saturation
behavior
Polarizing
voltage
99.0%
saturation
99.5%
saturation
Maximum dose rate at
continuous irradiation
150 V
5.9 Gy/s
2.9 Gy/s
300 V
24.0 Gy/s
12.0 Gy/s
400 V
42.0 Gy/s
21.0 Gy/s
150 V
0.7 mGy
0.4 mGy
Maximum dose rate
per irradiation pulse
300 V
1.4 mGy
0.7 mGy
400 V
1.9 mGy
0.9 mGy
See next page for more specifications.
Specifications
(continued)
Diagram
0.03
Protection/Waterproofing cap, PMMA
Ø 5 .3
Ø 6 .0
4.0
2.0
14. 0
Ø30. 0
Ø30. 0
Directional dependence
Eo = 15 MeV, Er = 2.7 MeV
Eo = 9.7 MeV , Er = 2.7 MeV
Eo = 15 MeV, Er = 10.2 MeV
110
10 5
120
0°
10 0
100
95
80
90
60
40
85
20
80
270°
0
90°
75
0
90
180
270
360
Angle [degrees]
in PMMA
Eo = 15 MeV, Er = 2.7 MeV
Eo = 9.7 MeV, Er = 2.7 MeV
Eo = 15 MeV, Er = 10.2 MeV
180°
The values given in the diagrams are typical for the construction.
Optional accessories
Check Source,
90
Sr, 20 MBq (541 µCi) (Model 30-658)
Available model(s)
30-329
Markus Electron Ionization Chamber, 0.055 cm
3
,
Waterproof, includes BNC Triax connector and PMMA buildup cap
Other types of triaxial cable connectors available
