| Autor: |
E J Axton, G P Barnard, A R S Marsh |
| Rok vydání: |
1959 |
| Předmět: |
|
| Zdroj: |
Physics in Medicine and Biology. 3:366-394 |
| ISSN: |
0031-9155 |
| DOI: |
10.1088/0031-9155/3/4/306 |
| Popis: |
The difficulties associated with the determination of the equilibrium wall thickness and the associated wall-absorption correction in a cavity ion chamber to be used with radiation of a particular quantum energy are discussed in some detail. It does not appear possible to devise any experiment to measure directly the γ-ray or X-ray absorption in the wall of the chamber. An analytical study has been made of total ionization versus wall-thickness curves from which the required wall-absorption correction is derived. It appears that electronic equilibrium is not fully achieved in the N.P.L. graphite cavity chambers; but since the wall-absorption correction at present applied is too large, partial compensation for lack of electronic equilibrium is fortuitously achieved. As a by-product of this analysis, a new method of deriving the relationship between total ionization and atomic number of wall material has been developed for a single chamber. It is suggested that this merits further experimental study with monoenergetic sources. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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