Abstract:
:Values of W (the mean energy required to create an ion pair when a charged particle is stopped in a gas) are needed in radiation dosimetry to convert ionisation chamber current readings to absorbed dose. For neutron dosimetry the most important W values are those for protons, and this paper describes absolute measurements for protons with energies between 1.2 and 3.5 MeV for methane-based tissue-equivalent gas and its constituent gases, i.e. methane, carbon dioxide and nitrogen. An ionisation chamber with a parallel-plate arrangement was used to determine the integrated charge created by a measured number of protons, and W values were determined with an estimated uncertainty of about +/- 0.5%. The results are presented and compared with previous measurements. In general the present data tend to be somewhat lower than previously reported values. Finally the accuracy of a formula for predicting W values for gas mixtures from the values for the individual constituents is investigated.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Thomas DJ,Burke Mdoi
10.1088/0031-9155/30/11/003subject
Has Abstractpub_date
1985-11-01 00:00:00pages
1201-13issue
11eissn
0031-9155issn
1361-6560journal_volume
30pub_type
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