Features
- Waterproof, wide guard ring design
- Sensitive volume 10.5 cm3, vented to air
The 34070 Bragg peak chamber is designed to measure the exact location of the Bragg peak in therapy proton beams. The large diameter of the chamber allows the measurement of the complete proton beam diameter (non-scanned), while avoiding the detection of protons scattered into the sensitive volume. The chamber is waterproof and consequently can either be used in air behind a water column or in a water phantom.
Specifications
| Type of product | vented plane parallel ionization chamber |
|---|---|
| Application | relative dosimetry in high-energy proton beams |
| Nominal sensitive volume | 10.5 cm3 |
| Design | waterproof, vented |
| Reference point | in chamber center, 3.5 mm from chamber surface |
| Direction of incidence | perpendicular to chamber plane, see label ‘Focus’ |
| Nominal response |
325 nC/Gy (at 60Co free in air) |
| Chamber voltage | 400 V nominal ± 500 V maximal |
| Polarity effect | < 1 % |
| Leakage current |
< ± 100 fA |
| Cable leakage | ≤ 1 pC/(Gy·cm) |
Materials and measures
| Entrance window |
3.47 mm PMMA 0.02 mm graphite 0.1 mm varnish |
|---|---|
| Total window area density | 411 mg/cm2 |
| Water-equivalent window thickness | 4 mm |
| Sensitive volume |
radius 42 mm depth 2 mm |
| Guard ring width | 1.1 mm |
Ion collection efficiency at nominal voltage
| Ion collection time | 277 µs |
|---|---|
| Max. dose rate for ≥ 99.5 % saturation ≥ 99.0 % saturation |
21 Gy/s 42 Gy/s |
| Max. dose per pulse for ≥ 99.5 % saturation ≥ 99.0 % saturation |
0.9 mGy 1.9 mGy |
Useful Ranges
| Chamber voltage | (300 … 500) V |
|---|---|
| Radiation quality | (70 … 250) MeV protons |
| Field size | diameter (3 … 10) mm |
| Temperature | (10 … 40) °C (50 … 104) °F |
| Humidity | (10 … 80) %, max 20 g/m3 |
| Air pressure | (700 … 1060) hPa |
Parts
TN34070-2,5 Bragg peak chamber 10.5 cm3, connecting system BNT
TW34070-2,5 Bragg peak chamber 10.5 cm3, connecting system TNC
TM34070-2,5 Bragg peak chamber 10.5 cm3, connecting system M
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