Radioactive beams by fragmentation and ISOL techniques - CERN

The absolute value of R depends on the acceptance of the spectrometer
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considered. For a reaction C(C, He) we find, for fiSOi=1, R :1800 for the LISEO
spectrometer and R :360 for SISSI13), for Ei = Ef and Ei : 50 MeV/nucleon. ln the
following we will use R :500.
MeV/nucleon.
We can now plot the behaviour of R as a function of incident energy, using
equation (10) on fig 4). In order to limit the number of parameters, we fixed Ef : 5
This figure 4) should be considered as qualitative, because as stated above, the
exact value or R depends on the spectrometer acceptance and on the reaction considered.
However, it allows us a general conclusion: if experiments with the secondary beam are
to be done at the energy of the primary beam (in units/nucleon), there is a break even
point of both methods at around 100 MeV/nucleon if the final yield is considered for a
given incident beam intensity The exact value of this energy depends on the ISOL
efficiency and the spectrometer characteristics considered.
lf low energy secondary beams are needed, the gain factor of the lsol method with
respect to slowed down products increase with the energy of the primary beam. So, for
low energies of the secondary beams the lsol method gives higher intensities and better
beam quality as long as the lsol efficiency is in a reasonable range (fisoi > 10*). For an
energy of the primary beam of about 100MeV/nucleon and of a final energy of
5MeV/nucleori the ratio R is about 1000 for fiSOi:0.0l as can be seen on figure 4)
b)Beams for ISOL-techniques
Up to now, we considered the same beam for the production of secondary beams
by fragmentation and ISOL techniques. In the lsol techniques the beam and the target
may be choosen more independantly than in the direct fragmentation technique, if target
residues are used. This means essentially that light ion beams of high intensity may be
used, such as high energy proton beams.
Here a delicate balance of production cross-section, range, and extraction
efficiency from the target will determine if light ion beams or heavy ion beams are more
efficient. As a general thumbrule, it turns out that heavy ion beams are. at same beam
power in units of Watt. are better for the production of ions below A ~100. whereas light
ion beams are more efficient for the production of secondary beams with A>l()0. Actual
limits for heavy ion beams in the 1 GeV region are 1-10 kW. Proton beams with about 1
GeV and more than 100 kW exist, and may be the most promising long range possibility
for the production of secondary beams. R+D programs for the use of these very intense
beams exist at Triumphm), PSIIS) and RAU6) and may show that the use of these very
intense beams for the present purpose is practical. A more detailed discussion may be
found in reference 17.18). OCR Output