Semiflex Ionization Chamber 31010
Standard therapy chamber for scanning systems and for reference dosimetry
- Waterproof, semiflexible design for easy mounting in scanning water phantoms
- Minimized directional response
- Sensitive volume of 0.125 cm3, vented
- Point dose patient QA with RUBY
The 31010 semiflexible chamber is the ideal compromise between small size for reasonable spatial resolution and large sensitive volume for precise dose measurements.
This makes the 31010 chamber to one of the most commonly used chambers in scanning water phantom systems.
The chamber volume of 0.125 cm3 gives enough signal to use the chamber also for high precision reference dose measurements.
The sensitive volume is approximately spherical resulting in a flat angular response and a uniform spatial resolution along all three axes of a water phantom.
Specifications
| Type of product | vented cylindrical ionization chamber |
| Application | reference dosimetry in radiotherapy beams |
| Measuring quantities | absorbed dose to water, air kerma, exposure |
| Reference radiation quality | 60Co |
| Design | waterproof, vented, guarded |
| Direction of incidence | radial |
| Nominal sensitive volume | 0.125 cm3 |
| Nominal response | 3.3 nC/Gy |
| Long-term stability | ≤ 1 % per year |
| Chamber voltage | 400 V nominal, ± 500 V maximal |
| Polarity effect at 60Co | < 2 % |
| Reference point | on chamber axis, 4.5 mm from detector tip |
| Photon energy response | ≤ ± 2 % (140 kV ... 280 kV) |
| ≤ ± 4 % (200 kV ... 60Co) | |
| ≤ ± 5 % (50 kV ... 150 kV) | |
| Directional response in water | ≤ ± 0.5 % for rotation around the chamber axis and for tilting of the axis up to ± 10° |
| Leakage current | ≤ ± 4 fA |
| Cable leakage | ≤ 1 pC/(Gy·cm) |
Materials and measures
| Wall of sensitive volume | 0.55 mm PMMA, 1.19 g/cm3 |
| 0.15 mm graphite, 0.82 g/cm3 | |
| Total wall area density | 78 mg/cm2 |
| Dimensions of sensitive volume | radius 2.75 mm |
| length 6.5 mm | |
| Central electrode | Al 99.98, diameter 1.1 mm |
| Build-up cap | PMMA, thickness 3 mm |
Ion collection efficiency at nominal voltage
| Ion collection time | 121 μs |
| Max. dose rate for | |
| ≥ 99.5 % saturation | 6 Gy/s |
| ≥ 99.0 % saturation | 112 Gy/s |
| Max. dose per pulse for | |
| ≥ 99.5 % saturation | 0.5 mGy |
| ≥ 99.0 % saturation | 1.0 mGy |
Ranges of use
| Chamber voltage | ± (100 ... 400) V |
| Radiation quality | 140 kV ... 50 MV photons |
| (10 ... 45) MeV electrons | |
| (50 ... 270) MeV protons | |
| Field size | (3 x 3) cm2 ... (40 x 40) cm2 |
| Temperature | (10 ... 40) °C |
| (50 ... 104) °F | |
| Humidity | (10 ... 80) %, max 20 g/m3 |
| Air pressure | (700 ... 1060) hPa |
Options
| T48012 | Radioactive check device 90Sr |
| T48002.1.004 | Chamber holding device for check device |
| T40072.1.160 | RUBY detector holder T31010 |
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