Features
- Waterproof, fully guarded chamber
- Sensitive volume 0.6 cm3, vented to air
- Acrylic wall, graphited Aluminum central electrode
- Radioactive check device (option)
The 30013 Farmer chamber is the standard ionization chamber for absolute dose measurements in radiation therapy. Correction factors needed to determine absorbed dose to water or air kerma are published in the pertinent dosimetry protocols. Its waterproof design allows the chamber to be used in water or in solid state phantoms. The acrylic chamber wall ensures the ruggedness of the chamber.
Specifications
| Type of product | vented cylindrical ionization chamber acc. IEC 60731 |
|---|---|
| Application | absolute therapy dosimetry in water, solid state phantoms and air |
| Measuring quantities | absorbed dose to water, air kerma, exposure |
| Reference radiation quality | 60Co |
| Nominal sensitive volume | 0.6 cm3 |
| Design | waterproof, vented, fully guarded |
| Reference point | on chamber axis, 13 mm from chamber tip |
| Direction of incidence | radial |
| Nominal response | 20 nC/Gy |
| Long-term stability | ≤ 0.5 % per year |
| Chamber voltage | 400 V nominal ± 500 V maximal |
| Polarity effect at 60Co | < 0.5 % |
| Photon energy response |
< ± 2 % (70 kV … 280 kV) < ± 4 % (200 kV … 60Co) |
| Directional response in water | < ± 0.5 % for rotation around the chamber axis and for tilting of the axis up to ± 5° |
| Leakage current | ≤ ± 4 fA |
| Cable leakage | ≤ 1 pC/(Gy·cm) |
Materials and measures
| Wall of sensitive volume |
0.335 mm PMMA, 1.19 g/cm3 0.09 mm graphite, 1.85 g/cm3 |
|---|---|
| Total wall area density | 56.5 mg/cm2 |
| Dimension of sensitive volume | radius 3.05 mm length 23.0 mm |
| Central electrode | Al 99.98, diameter 1.1 mm |
| Build-up cap | PMMA, thickness 4.55 mm |
Ion collection efficiency at nominal voltage
| Ion collection time | 140 µs |
|---|---|
| Max. dose rate for ≥ 99.5 % saturation ≥ 99.0 % saturation |
5 Gy/s 10 Gy/s |
| Max. dose per pulse for ≥ 99.5 % saturation ≥ 99.0 % saturation |
0.46 mGy 0.91 mGy |
Useful Ranges
| Chamber voltage | ± (100 … 400) V |
|---|---|
| Radiation quality | 30 keV … 50 MV photons (10 … 45) MeV electrons (50 … 270) MeV protons |
| Field size | (5 x 5) 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
T48002.3.003 Chamber holding device for check device
Parts
TN30013 Farmer type chamber 0.6 cm3, waterproof, connecting system BNT
TW30013 Farmer type chamber 0.6 cm3, waterproof, connecting system TNC
TM30013 Farmer type chamber 0.6 cm3, waterproof, connecting system M
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