Counts per minute
Encyclopedia
Counts per minute is a measure of radioactivity. It is the number of atom
s in a given quantity of radioactive material that are detected to have decayed in one minute. Disintegrations per minute (dpm) is also a measure of radioactivity. It is the number of atoms in a given quantity of radioactive material that decay in one minute. Dpm is similar to cpm, however the efficiency of the radiation detector (e.g. scintillation counter
) must be accounted for when analysing data in cpm. Dpm is the number of atoms that have decayed, not the number of atoms that have been measured as decayed. Dpm is commonly used as a measure of radioactive contamination
.
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
s in a given quantity of radioactive material that are detected to have decayed in one minute. Disintegrations per minute (dpm) is also a measure of radioactivity. It is the number of atoms in a given quantity of radioactive material that decay in one minute. Dpm is similar to cpm, however the efficiency of the radiation detector (e.g. scintillation counter
Scintillation counter
A scintillation counter measures ionizing radiation. The sensor, called a scintillator, consists of a transparent crystal, usually phosphor, plastic , or organic liquid that fluoresces when struck by ionizing radiation. A sensitive photomultiplier tube measures the light from the crystal...
) must be accounted for when analysing data in cpm. Dpm is the number of atoms that have decayed, not the number of atoms that have been measured as decayed. Dpm is commonly used as a measure of radioactive contamination
Radioactive contamination
Radioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places...
.
- One becquerelBecquerelThe becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
(Bq) is equal to one disintegration per second; One becquerel (Bq) is equal to 60 dpm. - One curieCurieThe curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...
(Ci) is equal to 3.7 x 10 10 Bq or dps, which is equal to 2.22 x 1012 dpm.