The non-SI unit of exposure, symbol R, defined by the electric charge produced in a kilogram of air by X or gamma rays (2.58 times 10 to the minus 4 coulombs per kilogram). One roentgen corresponds to slightly less than 1 rad in soft tissue, so for gamma fields technicians often treat R, rad and rem as roughly interchangeable. Many survey meters, especially analog ones, read in mR/h or R/h.
Old cutie pie reads in R per hour, so 200 milliR on contact is close enough to 200 millirem for gamma.
Also heard as
- R
Related terms
Rem
The US customary unit of dose equivalent, equal to one hundredth of a sievert.
Exposure
Being subjected to ionising radiation, from outside the body or from material within it.
Survey meter
A portable instrument used to measure radiation dose rates or detect contamination in the field.
Cutie pie
Nickname for a handheld ion chamber survey meter, taken from a classic pistol-grip design.