Features
- Vented sensitive volume of 17.6 cm3
- Shadow-free transmission chamber for dose monitoring with radiation therapy X-ray equipment
The circular plane parallel transmission chamber model 7862 is used for dose monitoring in combination with radiotherapy X-ray units. The sensitive volume is designed as a very thin cylinder of 2.4 mm thickness and 96.5 mm diameter. The chamber wall and the electrode are made of polyimide (PI) of 0.05 mm thickness each with graphite layer, mechanically protected by another PI foil of 0.05 mm in front of each wall. The nominal photon energy range is 7.5 kV up to 420 kV and the leakage current is less than 1 pA. The chamber is fully guarded. The external diameter of the chamber housing is 119.5 mm. Three holes with 3.5 mm threads serve for mechanical chamber fixation. The transmission chamber model 7862 is used in connection with dosemeters having the input circuits on ground potential.
Specifications
| Type of product | vented plane parallel triple-chamber |
|---|---|
| Application | dose monitoring in X-ray therapy units |
| Measuring quantity |
exposure |
| Nominal sensitive volume | 17.6 cm3 |
| Design | not waterproof, vented |
| Nominal response | depends on field size |
| Chamber voltage | 500 V nominal |
| Leakage current | ≤ 1 pA |
Materials and measures
| Entrance window |
4 x 0.05 mm polyimide, graphite coated |
|---|---|
| Total window area density | 4 x 7.1 mg/cm2 |
| Electrode | polyimide foil, graphite coated |
| Outer dimensions | diameter 119.5 mm |
Ion collection efficiency at nominal voltage
|
Max. dose rate for ≥ 99.5 % saturation ≥ 99.0 % saturation |
12.5 Gy/s 25 Gy/s |
|---|---|
| Max. dose per pulse for ≥ 99.5 % saturation ≥ 99.0 % saturation |
500 µGy |
Useful Ranges
| Radiation quality | (7.5 … 420) kV X-rays |
|---|---|
| Field size | ≤ 95 mm diameter |
| Temperature | (10 … 40) °C (50 … 104) °F |
| Humidity | (10 … 80) %, max 20 g/m3 |
| Air pressure | (700 … 1060) hPa |
Parts
TM7862 Monitor chamber for X-ray therapy units, connecting system M
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