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Equilibration of air temperature inside the thimble of a Farmer‐type ion chamber
Author(s) -
Tailor R. C.,
Chu C.,
Followill D. S.,
Hanson W. F.
Publication year - 1998
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.598226
Subject(s) - ionization chamber , imaging phantom , ionization , materials science , dosimetry , diffusion , ion , temperature measurement , atomic physics , nuclear engineering , optics , nuclear medicine , physics , thermodynamics , medicine , engineering , quantum mechanics
Ionization chambers are frequently moved from one environment to another, sometimes with significant differences in temperature between the chamber and measurement phantom. To obtain reliable ionization data, the temperature of the air in the chamber must be allowed to equilibrate with the measuring phantom. The air temperature inside a thimble of a Farmer‐type ion chamber was measured as a function of time for various phantom materials (air, water, and plastic). Equilibration rates for the various conditions are presented. Heat‐diffusion theory is presented to explain the characteristics of the measured data. Waiting times for temperature equilibration down to 10% of the initial temperature difference ranges from 1 to 18 min, depending on the phantom material and use of bare or covered thimble. Radiation measurements confirm the temperature data.