16] and is illustrated in Figure 3.9. A device of this type for thimble chambers has a ring-shaped source of ⁹⁰Sr housed within a fully-shielded enclosure, into the centre of which the sensitive volume of the ionization chamber can be accurately placed. ⁹⁰Sr is a beta emitter and decays at a constant rate with a half-life of 28.7 years. The chamber response within the device is measured at the time at which intercomparison measurements are made. The response to be expected at any subsequent time can then be calculated simply by accounting for radioactive decay, on the proviso that repositioning of the ionization chamber can be carried out with sufficient precision. Different source geometries may be used for different types of ionization chamber, for example planar ⁹⁰Sr sources may be used to check the consistency of response of parallel plate ionization chambers.

Figure 3.9 Strontium checking device used to check the consistency of a thimble chamber, together with a schematic of the device showing the source wrapped around the chamber.

Related posts:

descriptors of the radionuclide imaging process Radiotherapy beam production photon therapy trends Dentition

Stay updated, free articles. Join our Telegram channel

Join