Features
- Perturbation-free, minimized polarity effect
- Waterproof, wide guard ring design
- Sensitive volume 0.35 cm3, vented to air
- Radioactive check device (option)
The 34001 Roos chamber is the golden standard for absolute dose measurements in high-energy electron beams. Modern dosimetry protocols refer to the chamber’s design and provide dosimetric correction factors. Its waterproof design allows the chamber to be used in water or in solid state phantoms. The Roos chamber is also well suited for the measurement of high-energy photon depth dose curves up to 2.5 mm below the water surface. The chamber can be used for dose measurements of proton beams.
Specifications
| Type of product | vented plane parallel ionization chamber acc. IEC 60731 |
|---|---|
| Application | absolute dosimetry in high-energy electron and proton beams |
| Measuring quantity | absorbed dose to water |
| Reference radiation quality | 60Co |
| Nominal sensitive volume |
0.35 cm3 |
| Design | waterproof, vented |
| Reference point | in chamber center, 1.1 mm below surface |
| Direction of incidence | perpendicular to chamber plane, see label FOCUS |
| Nominal response | 10 nC/Gy |
| Long-term stability | ≤ 0.5 % per year |
| Chamber voltage | 200 V nominal ± 400 V maximal |
| Polarity effect | < 0.5 % |
| Directional response in water |
< ± 0.1 % for chamber tilting < ± 10° |
| Leakage current | ≤ ± 4 fA |
| Cable leakage | ≤ 1 pC/(Gy·cm) |
Materials and measures
| Entrance window |
1 mm PMMA, 1.19 g/cm3 0.02 mm graphite, 0.82 g/cm3 0.1 mm varnish, 1.19 g/cm3 |
|---|---|
| Total window area density | 132 mg/cm2 |
| Water-equivalent window thickness | 1.3 mm |
| Sensitive volume | radius 7.5 mm depth 2 mm |
|
Guard ring width |
4 mm |
Ion collection efficiency at nominal voltage
| Ion collection time | 125 µs |
|---|---|
| Max. dose rate for ≥ 99.5 % saturation ≥ 99.0 % saturation |
5.2 Gy/s 10.4 Gy/s |
| Max. dose per pulse for ≥ 99.5 % saturation ≥ 99.0 % saturation |
0.46 mGy 0.93 mGy |
Useful Ranges
| Chamber voltage | ± (50 … 300) V |
|---|---|
| Radiation quality |
(2 … 45) MeV electrons 60Co … 25 MV photons (70 … 250) MeV protons |
| Field size | (4 x 4) 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
T48010 Radioactive check device 90Sr
T48004 Chamber holding device for check device
Parts
TN34001 Roos electron chamber 0.35 cm3, connecting system BNT
TW34001 Roos electron chamber 0.35 cm3, connecting system TNC
TM34001 Roos electron chamber 0.35 cm3, connecting system M
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