Radioactive Check Source,
90 Sr, 33 MBq (892 µCi)
The Radioactive Check Source, Model 30-657, provides
the Medical Physicist with an easy way to check the
constancy of response of compact thimble type
ionization chambers. The device contains 33.3 MBq of
90 Sr, in a fully shielded container, and is equivalent to
ISO Class C43323. Holders for reproducible chamber
positioning during check measurements are available
for a variety of ion chambers.
• Radioactive check device for constancy
checks of thimble-type ion chambers
• Checks for proper functioning of the
complete dosimetry system
• Holders available for a variety of thimble-
Use of the Radioactive Check Source, Model 30-657, 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 properly. Since the radioactive source is in the shape of a tube, the
chamber volume is irradiated from all directions.
Radioactive content 33.3 MBq (892 µCi)
Check readings must be corrected for the 28.7 year half-life time of the 90 Sr source.
However, under constant environmental conditions (temperature, pressure, air
humidity) the current produced in an ionization chamber is reproducible with an
Half-value time 28.7 years
Holder for 0.6 cm³ Farmer-Type
(Models 580-006-WP and 30-351) Ion Chambers
uncertainty of ± 1%.
Holders to assure correct positioning and repositioning accuracy for the 0.6 cm3
Farmer-type chambers (Models 580-006-WP and 30-351), 0.125 cm³
Semiflex™ chamber (Models 30-344), 0.3 cm³ Semiflex™ chamber (Models 30-316),
and 0.015 cm3PinPoint™ chamber (Model 30-350) are available. If this device is
used with other types of chambers, proper positioning becomes the responsibility
of the user.
Holder for 0.125 and 0.3 cm³ Semiflex (Model
30-344 and 30-316) Ion Chambers
Holder for 0.015 cm³ PinPoint (Model 30-350)
Radioactive Check Source, 90Sr, 33 MBq (892 µCi).
A radioactive materials license is required
The Radioactive Check Source, Model 30-657, is equipped with an attached
thermometer. When making check measurements 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.
A radioactive materials license for 90Sr is required for purchase.