Editing Radioactive tracer (section)

== Production ==
The commonly used radioisotopes have short [[half life|half lives]] and so do not occur in nature in large amounts. They are produced by [[nuclear reaction]]s. One of the most important processes is absorption of a  neutron by an atomic nucleus, in which the mass number of the element concerned increases by 1 for each neutron absorbed. For example,
:[[carbon|<sup>13</sup>C]] + [[neutron|n]] → [[carbon|<sup>14</sup>C]]
In this case the atomic mass increases, but the element is unchanged. In other cases the product nucleus is unstable and decays, typically emitting protons, electrons ([[beta particle]]) or [[alpha particle]]s. When a nucleus loses a proton the [[atomic number]] decreases by 1. For example,
:[[sulfur|<sup>32</sup>S]] + [[neutron|n]] → [[phosphorus|<sup>32</sup>P]] + [[proton|p]]
Neutron irradiation is performed in a [[nuclear reactor]]. The other main method used to synthesize radioisotopes is proton bombardment. The proton are accelerated to high energy either in a [[cyclotron]] or a [[linear accelerator]].<ref name=fowler/>