Spherical Chamber TK-30

Spherical ionization chamber with a long rigid stem for radiation protection measurement

  • Vented sensitive volume of 28 cm³
  • Suitable as high precision reference chamber for radiation protection dosimetry
  • Very flat energy response within a wide range

The spherical graphite chamber TK-30 has been designed as a reference chamber for absolute dosimetry to be used by secondary standard dosimetry laboratories (SSDL) and users with high quality requirements.
It has very small variations of response with radiation quality from low X-ray energies up to high-energy photon radiation.

The guard ring is designed up to the sensitive volume. The chamber is constructed with a long rigid stem of approx. 20 cm length for easy mounting in the radiation beam. Air density correction is required for each measurement.

Type of product vented spherical
  ionization chamber
Application radiation protection measurement
Measuring quantities photon equivalent dose, exposure
Design not waterproof, vented
Nominal sensitive volume 27.9 cm³
Reference point chamber center
Direction of incidence radial
Nominal response 900 nC/Gy
Chamber voltage 400 V nominal, ± 1000 V maximal
Energy response ≤ ± 5 % (48 keV ... 60Co)
Directional response in air ≤ ± 0.5 % for rotation around the chamber axis
  and ≤ ± 3 % for tilting of the chamber axis up to ± 45°
Leakage current ≤ ± 5 fA

Materials and measures

Wall of sensitive volume 3 mm POM
  0.02 mm graphite
  0.22 mm lacquer
Total wall area density 453 mg/cm2
Dimension of sensitive volume  
Central electrode graphite coated PMMA,
  diameter 4.2 mm

Ion collection efficiency at nominal voltage

Ion collection time 4.5 ms
Max. dose rate for ≥ 99 % saturation 29.4 mGy/s
Max. dose per pulse for ≥ 99 % saturation 26 μGy

Ranges of use

Chamber voltage ± (200 ... 1000) V
Radiation quality 25 keV ... 50 MeV
Temperature (10 ... 40) °C
  (50 ... 104) °F
Humidity (10 ... 80) %, max 20 g/m3
Air pressure (700 ... 1060) hPa
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