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Counts per minute (abbreviated to cpm) is a measure of the detection rate of ionization events per minute. Counts are only manifested in the reading of the measuring instrument, and are not an absolute measure of the strength of the source of radiation. Whilst an instrument will display a rate of cpm, it does not have to detect counts for one ...
The curie (symbol Ci) is a non-SI unit of radioactivity originally defined in 1910. According to a notice in Nature at the time, it was to be named in honour of Pierre Curie , [ 1 ] but was considered at least by some to be in honour of Marie Skłodowska-Curie as well, [ 2 ] and is in later literature considered to be named for both.
The counts display is the simplest, and shows the number of ionizing events detected, displayed either as a count rate, such as "counts per minute" or "counts per second", or as a total number of counts over a set time period (an integrated total). The counts readout is normally used when alpha or beta particles are being detected.
curie: Ci 3.7 × 10 10 s −1: 1953 3.7 × 10 10 Bq rutherford: Rd 10 6 s −1: 1946 1 000 000 Bq Exposure (X) coulomb per kilogram: C/kg C⋅kg −1 of air 1974 SI unit
They find wide use in situations where a constant high dose rate is being measured as they have a greater operating lifetime than standard Geiger–Müller tubes, which suffer from gas break down and are generally limited to a life of about 10 11 count events. [1] Additionally, the Geiger–Müller tube cannot operate above about 10 4 counts ...
Count rate measurements are normally associated with the detection of particles, such as alpha particles and beta particles. However, for gamma ray and X-ray dose measurements a unit such as the gray or sievert is normally used. The following table shows ionising radiation quantities in SI and non-SI units.
count of photons n with energy Q p = h c/λ. [nb 2] photon flux: Φ q: count per second: s −1: T −1: photons per unit time, dn/dt with n = photon number. also called photon power: photon intensity: I: count per steradian per second sr −1 ⋅s −1: T −1: dn/dω: photon radiance: L q: count per square metre per steradian per second m − ...
Specific activity (symbol a) is the activity per unit mass of a radionuclide and is a physical property of that radionuclide. [1] [2] It is usually given in units of becquerel per kilogram (Bq/kg), but another commonly used unit of specific activity is the curie per gram (Ci/g).