The heart of an on-line isotope separator is its target and ion source. The target
should assure a fast liberation of the radioactive nuclei produced in large amounts of
target material. The combination with the ion-source should be able to produce an ion beam
which preferably should only contain isotopes from one chemical element. The development
of this experimental technique is a field of radiochemistry, which also involves
metallurgy, high temperature chemistry and surface physics. The ISOLDE group has developed
many different advanced target-ion-source combinations, which have allowed the users of
the facility to study radioisotopes from more than 60 different elements. the elements for
which beams are available at ISOLDE today are indicated in the periodic table, which also
allows to obtain information on the produced quantities.
Some of the targets used at ISOLDE consist of molten metals kept at temperatures from
700o C and up to about 1400o C. Such targets are characterized by a
relatively long release time of the produced isotopes and a typical time constant of the
release is about 30 seconds. Faster release times, in the order of one second or less, can
be obtained, if target material in the form of refractory metal powder, metals or carbides
is used at temperatures above 2000o C. An expected decrease in the release time
due to the "shock-wave" effect of the pulsed proton beam has been observed. Time
constants down to some tenths of a second can be reached for the fastest targets.
Currently there are three different types of ion sources in use at ISOLDE: