X-ray (unit)

Physical unit
Unit name	roentgen
Unit symbol	${\displaystyle \mathrm {R} }$
Physical quantity (s)	Ion dose
Formula symbol	${\displaystyle J}$
dimension	${\displaystyle {\mathsf {M^{-1/2}L^{3/2}T^{-1}}}}$
In SI units	${\displaystyle \mathrm {1\,R\sim 2{,}58\cdot 10^{-4}\;{\frac {C}{kg}}} }$
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The X-ray (abbreviation: R) is an outdated unit of measurement for the ion dose .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 ):

${\displaystyle \mathrm {1\,R=2{,}58\cdot 10^{-4}\,{\frac {C}{kg}}} }$

${\displaystyle \mathrm {1\,{\frac {C}{kg}}\approx 3{,}876\cdot 10^{3}\,R} }$

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

• List of units of measurement relevant to radiation protection

Individual evidence

1. ↑ Herman Cember: Introduction to health physics . In: Introduction to health physics . 1969 (English).
2. ↑ Ulrike Koller: Radioactivity and Radiation - Basic Terms. (PDF; 785 kB) Bavarian State Office for the Environment, p. 6 , accessed on December 7, 2009 . 
3. ^ 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]).