Features
- Fully guarded chamber
- Sensitive volume 0.3 cm3, vented to air
- Acrylic wall, graphited
- Aluminum central electrode
- Radioactive check device (option)
The 23332 chamber is used for absolute dose measurements in radiation therapy in cases where the high volume of the 23331 chamber is not needed and a higher spatial resolution is needed. Correction factors needed to determine absorbed dose to water or air kerma are published in the pertinent dosimetry protocols. The acrylic chamber wall ensures the ruggedness of the chamber. The chamber is designed for the use in solid state phantoms and is therefore not waterproof.
Specifications
| Type of product | vented cylindrical ionization chamber |
|---|---|
| Application | absolute dosimetry in radiotherapy beams |
| Measuring quantities |
absorbed dose to water, air kerma, exposure |
| Reference radiation quality | 60Co |
| Nominal sensitive volume |
0.3 cm3 |
| Design | not waterproof, vented, fully guarded |
| Reference point |
on chamber axis, 9.5 mm from chamber tip |
| Direction of incidence | radial |
| Nominal response | 10 nC/Gy |
| Long-term stability |
≤ 1 % per year |
| Chamber voltage | 400 V nominal ± 500 V maximal |
| Polarity effect at 60Co | < 0.5 % |
| Photon energy response |
< ± 2 % (140 kV … 250 kV)
< ± 4 % (200 kV … 60Co) |
| Directional response in solid state phantom |
< ± 0.5 % for rotation around the chamber axis,
< ± 1 % for tilting of the axis up to ± 30° |
| Leakage current | ≤ ± 4 fA |
| Cable leakage | ≤ 1 pC/(Gy·cm) |
Materials and measures
| Wall of sensitive volume | 0.35 mm PMMA, 1.19 g/cm3 0.15 mm graphite, 0.82 g/cm3 |
|---|---|
| Total wall area density | 54 mg/cm2 |
| Dimension of sensitive volume |
radius 5 mm |
| Central electrode | Al 99, diameter 2 mm |
| Build-up cap | PMMA, thickness 3 mm |
Ion collection efficiency at nominal voltage
| Ion collection time | 40 µs |
|---|---|
| Max. dose rate for ≥ 99.5 % saturation ≥ 99.0 % saturation |
54 Gy/s 105 Gy/s |
| Max. dose per pulse for ≥ 99.5 % saturation ≥ 99.0 % saturation |
1.0 mGy 2.5 mGy |
Useful Ranges
| Chamber voltage | ± (100 … 400) V |
|---|---|
| Radiation quality |
70 keV … 50 MV photons (10 … 45) MeV electrons |
| Field size | (5 x 5) cm2 … (40 x 40) cm2 |
| Temperature | (10 … 40) °C (50 … 104) °F |
| Humidity | (20 … 75) %, max 20 g/m3 |
| Air pressure | (930 … 1050) hPa |
Options
T48012 Radioactive check device 90Sr
T48002.3.004 Chamber holding device for check device
Parts
TN23332 Rigid stem chamber 0.3 cm3, connecting system BNT
TW23332 Rigid stem chamber 0.3 cm3, connecting system TNC
TM23332 Rigid stem chamber 0.3 cm3, connecting system M
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