Editing Ion source (section)

==Thermal ionization==
{{Main|Thermal ionization}}
Thermal ionization (also known as surface ionization, or contact ionization) involves spraying vaporized, neutral atoms onto a hot surface, from which the atoms re-evaporate in ionic form. To generate positive ions, the atomic species should have a low [[ionization energy]], and the surface should have a high [[work function]]. This technique is most suitable for [[alkali metal|alkali]] atoms (Li, Na, K, Rb, Cs) which have low ionization energies and are easily evaporated.<ref name="Alton1988">{{cite journal|last1=Alton|first1=G. D.|title=Characterization of a cesium surface ionization source with a porous tungsten ionizer. I|journal=Review of Scientific Instruments|volume=59|issue=7|date=1988|page=1039|issn=0034-6748|doi=10.1063/1.1139776|bibcode=1988RScI...59.1039A|url=https://zenodo.org/record/1231832|type=Submitted manuscript}}</ref>

To generate negative ions, the atomic species should have a high [[electron affinity]], and the surface should have a low work function. This second approach is most suited for [[halogen]] atoms Cl, Br, I, At.<ref>{{Cite web |url=http://www.ornl.gov/~webworks/cpr/v823/pres/110496.pdf |title=A Negative-Surface Ionization for Generation of Halogen Radioactive Ion Beams |access-date=2014-01-20 |archive-url=https://web.archive.org/web/20041218073009/http://www.ornl.gov/~webworks/cpr/v823/pres/110496.pdf |archive-date=2004-12-18 |url-status=dead }}</ref>