Radiation Therapy
Radioactive Check Source,
90 Sr, 20 MBq (541 µCi)
Model 30-658
The Radioactive Check Source, Model 30-658, provides
• Radioactive check device for constancy
checks of flat plane-parallel type ion
the Medical Physicist with an easy way to check the
constancy of response of flat plane-parallel type
• Checks for proper functioning of the
complete dosimetry system
ionization chambers. The device contains 20 MBq of 90 Sr
in a fully shielded container, and is equivalent to
ISO Class C64444. Holders for reproducible chamber
• Holders available for Markus™, Advanced
Markus™, and Roos™ ion chambers
positioning during check measurements are available
for the Markus, Advanced Markus, and Roos ion
Use of the Radioactive Check Source, Model 30-658, is recommended for high
precision dosimetry and is required by IEC 60731 - Dosimeters with ionization
chambers as used in radiotherapy, 1977. A check measurement performed
before each dose measurement will assure the ionization chamber is responding
Radioactive content 20 MBq (541 µCi)
properly. Since the radioactive source is cylindrical, the entrance window of the flat
plane-parallel is placed near the source by means of the appropriate holding device.
Half-value time 28.7 years
Optional accessories
Check readings must be corrected for the 28.7 year half-life time of the 90 Sr source.
Holder for 0.055 cm 3 Markus (Model 30-329)
and 0.02 cm 3 Advanced Markus (Model 30-331)
Electron Ion Chambers Model 30-658-1000
However, under constant environmental conditions (temperature, pressure, air
humidity) the current produced in an ionization chamber is reproducible with an
uncertainty of ± 1%.
Holder for 0.35 cm 3 Roos (Model 30-332)
Electron Ion Chamber Model 30-658-2000
Holders to assure correct positioning and repositioning accuracy for the 0.055 cm 3
Available model(s)
Markus chamber (Model 30-329), 0.02 cm 3 Advanced Markus chamber (Model 30-331),
30-658 Radioactive Check Source,
90Sr, 20 MBq (541 µCi).
A radioactive materials license is required
and 0.35 cm3 Roos chamber (Model 30-332) are available. If this device is used with
other types of chambers, proper positioning becomes the responsibility of the user.
When making check measurements with the Radioactive Check Source, Model 30-658,
care must be taken to obtain temperature equilibrium between the ionization
chamber, check device, and the surrounding environment. After use, the protective
cover should be replaced and secured. With the protective cover in place the dose rate
from the source is reduced to less than 1 µSv/h at 10 cm. Leaving an ionization
chamber in the check device when not in use is not recommended since this can
damage the ion chamber.
Note: A radioactive materials license for 90Sr is required for purchase.