Editing Isotope separation (section)

==Isotope separators for research==
Radioactive beams of specific isotopes are widely used in the fields of experimental physics, biology and materials science. The production and formation of these radioactive atoms into an ionic beam for study is an entire field of research carried out at many laboratories throughout the world. The first isotope separator was developed at the Copenhagen Cyclotron by Bohr and coworkers using the principle of electromagnetic separation. Today, there are many laboratories around the world that supply beams of radioactive ions for use. 

Arguably the principal '''Isotope Separator On Line (ISOL)''' is ISOLDE at CERN,<ref>{{cite web |url=https://isolde.cern/ |title=ISOLDE official webpage}}</ref> which is a joint European facility spread across the Franco-Swiss border near the city of Geneva. This laboratory uses mainly proton spallation of uranium carbide targets to produce a wide range of radioactive fission fragments that are not found naturally on earth. During spallation (bombardment with high energy protons), a uranium carbide target is heated to several thousand degrees so that radioactive atoms produced in the nuclear reaction are released. 

Once out of the target, the vapour of radioactive atoms travels to an ionizer cavity. This ionizer cavity is a thin tube made of a refractory metal with a high [[work function]] allowing for collisions with the walls to liberate a single electron from a free atom ([[surface ionization]] effect). Once ionized, the radioactive species are accelerated by an electrostatic field and injected into an electromagnetic separator. As ions entering the separator are of approximately equal energy, those ions with a smaller mass will be deflected by the magnetic field by a greater amount than those with a heavier mass. This differing radius of curvature allows for isobaric purification to take place. 

Once purified isobarically, the ion beam is then sent to the individual experiments. In order to increase the purity of the isobaric beam, laser ionization can take place inside the ionizer cavity to selectively ionize a single element chain of interest. At CERN, this device is called the Resonance Ionization Laser Ion Source (RILIS).<ref>{{cite web |url=https://isolde.cern/rilis |title=Isolde RILIS}}</ref> Currently over 60% of all experiments opt to use the RILIS to increase the purity of radioactive beams.

===Beam production capability===
As the production of radioactive atoms by the ISOL technique depends on the free atom chemistry of the element to be studied, there are certain beams which cannot be produced by simple proton bombardment of thick actinide targets. [[Refractory]] metals such as tungsten and rhenium do not emerge from the target even at high temperatures due to their low vapour pressure. In order to produce these types of beams, a thin target is required. The Ion Guide Isotope Separator On Line (IGISOL) technique was developed in 1981 at the University of Jyväskylä [[cyclotron]] laboratory in [[Finland]].<ref>{{cite web |url=http://www.jyu.fi/science/laitokset/fysiikka/en/research/accelerator/igisol |title=IGISOL — Fysiikan laitos |language=fi |publisher=Jyu.fi |access-date=2014-02-18 |archive-date=2008-05-02 |archive-url=https://web.archive.org/web/20080502133759/http://www.jyu.fi/science/laitokset/fysiikka/en/research/accelerator/igisol |url-status=dead }}</ref> In this technique, a thin uranium target is bombarded with protons and nuclear reaction products recoil out of the target in a charged state. The recoils are stopped in a gas cell and then exit through a small hole in the side of the cell where they are accelerated electrostatically and injected into a mass separator. This method of production and extraction takes place on a shorter timescale compared to the standard ISOL technique and isotopes with short half-lives (sub millisecond) can be studied using an IGISOL. An IGISOL has also been combined with a laser ion source at the Leuven Isotope Separator On Line (LISOL) in Belgium.<ref>{{cite web |url=https://fys.kuleuven.be/iks/ns/lisol-leuven-isotope-separator-on-line|title=LISOL @ KU Leuven}}</ref> Thin target sources generally provide significantly lower quantities of radioactive ions than thick target sources and this is their main drawback.

As experimental nuclear physics progresses, it is becoming more and more important to study the most exotic of radioactive nuclei. In order to do so, more inventive techniques are required to create nuclei with extreme proton/neutron ratios. An alternative to the ISOL techniques described here is that of fragmentation beams, where the radioactive ions are produced by fragmentation reactions on a fast beam of stable ions impinging on a thin target (usually of beryllium atoms). This technique is used, for example, at the [[Facility for Rare Isotope Beams]] (FRIB) at Michigan State University and at the [[Radioactive Isotope Beam Factory]] (RIBF) at [[RIKEN]], in Japan.