Measurement
The human body cannot sense ionizing radiation, but the effects of ionization can be used to characterize the radiation. Parameters of interest include disintegration rate, particle flux, particle type, beam energy, kerma, dose rate and cummulative dose received by a target. Particle type is determined by differential measurements in the presence of electrical fields, magnetic fields, or varying amounts of shielding. Dose values may represent absorbed, equivalent, effective, or committed dose. The monitoring and calculation of doses to safeguard human health is called dosimetry.
| Quantity | Particle detector | CGS units | SI units | Other units |
|---|---|---|---|---|
| Disintegration rate | curie | becquerel | ||
| Particle flow rate | geiger counter, proportional counter, scintillator | counts per minute | ||
| Fluence | thermoluminescent dosimeter, Film badge dosimeter | joule/metre2 | ||
| Beam energy | proportional counter | electronvolt | joule | |
| Kerma | ionization chamber, semiconductor detector, quartz fiber dosimeter, Kearny Fallout Meter | esu/cm3 | coulomb/kilogram | roentgen |
| Absorbed dose | calorimeter | rad | gray | rep |
| Equivalent dose | derived quantity | rem | sievert | |
| Effective dose | derived quantity | rem | sievert | BRET |
| Committed dose | derived quantity | rem | sievert | banana equivalent dose |
Radiation measuring instruments are commonly calibrated to provide readouts of more sophisticated quantities than what is actually measured. For example, most dosimeter give instantaneous readouts of equivalent dose or even effective dose, even though the directly measured quantity is actually fluence or sometimes kerma. Such calibrations make assumptions about the radiation type, beam energy, field uniformity, and penetrating power based on the expected use of the instrument. These assumptions are not universally applicable, and may produce very erroneous readings in some situations.
Read more about this topic: Ionizing Radiation
Famous quotes containing the word measurement:
“That’s the great danger of sectarian opinions, they always accept the formulas of past events as useful for the measurement of future events and they never are, if you have high standards of accuracy.”
—John Dos Passos (1896–1970)