X-ray (unit)
Physical unit | |
---|---|
Unit name | roentgen |
Unit symbol | |
Physical quantity (s) | Ion dose |
Formula symbol | |
dimension | |
In SI units | |
Named after | Wilhelm Conrad Röntgen |
Derived from | Franklin (unit) , cubic centimeter |
See also: Gray |
The X-ray (abbreviation: R) is an outdated unit of measurement for the ion dose . It was named after the German physicist Wilhelm Conrad Röntgen .
Demarcation
The unit X-ray was defined as the amount of radiation necessary to release positive and negative ions from a Franklin (an electrostatic unit, unit of charge in the cgs system ) in a volume of one cubic centimeter (1 cm³) of air under normal conditions through its ionizing effect . This corresponds approximately to the amount of radiation of 0.00877 Gray in dry air and 0.0096 Gray in tissue.
The SI unit for the ion dose is coulombs per kilogram ( C kg −1 ):
In other words, a dose of 1 x-ray per cubic centimeter of air creates about 2 billion ion pairs.
The unit symbol r was originally introduced for x-ray . The definition was established in Stockholm in 1928 in the guidelines of an international commission and reformulated in 1953 at a meeting of the International Commission on Radiation Units and Measurement in Copenhagen.
In the European Union , Directive 80/181 / EEC made the International System of Units (SI) mandatory. Since December 31, 1985, the sole use of the X-ray unit is no longer permitted in business transactions.
See also
Individual evidence
- ↑ Herman Cember: Introduction to health physics . In: Introduction to health physics . 1969 (English).
- ↑ Ulrike Koller: Radioactivity and Radiation - Basic Terms. (PDF; 785 kB) Bavarian State Office for the Environment, p. 6 , accessed on December 7, 2009 .
- ^ The Council of the European Communities: Council Directive 80/181 / EEC of 20 December 1979 on the approximation of the laws of the Member States relating to Unit of measurement and on the repeal of Directive 71/354 / EEC . December 21, 1979 (English, EUR-Lex [accessed October 18, 2013]).