Model 44G Well Chamber
for LDR, HDR and IVR
The 44G is a hermetically-sealed re-entrant well ion chamber, requiring no air density corrections. The fill gas is pure argon at an absolute pressure of 23.5 psi, which provides three distinct benefits. First, through photoelectric absorption, argon enhances the response at low energies emitted from 125I and 103Pd. Second, because of its low electron attachment coefficient, argon provides a higher ion collection efficiency, making it more suitable for 10 Ci HDR 192Ir sources. Third, the positive pressure provides long term constancy measurements with the ability to verify the chamber seal.
The 44G is fully guarded into the chamber and is equipped with a 1.5 meter triaxial cable. It may be connected to any precision, dosimetry-grade electrometer. To cover the entire range of clinical sources from 125I (Iodine-125) seeds to HDR 192Ir (Iridium-192), the electrometer should be capable of resolving at least 10 fA and measure up to 2000 nA or 20,000 nC.