Heavy and super-heavy elements
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For the synthesis of heavy elements, we notice that we begin to reach so weak production yields that we have either to go to a more advanced accelerator generation, a bit what we expect with LINAG and the S3 spectrometer, or find new entrance channels that could be competitive with the ones explored until now, as the cold fusion on lead target or the hot fusion on actinide target. As we have confirmation of very weak cross sections for the heaviest elements, as, for example, the 55 fb for the Z=113 obtained by the Japanese, we do not have the feeling to be able to continue much more on our current impetus, except if we go to beams that would have a factor 10 or 100 more in intensity with LINAG-type accelerators. On the other hand, the hot fusion using actinides targets still requires more intense studies, as the decrease of the cross sections doesn’t seem so steep as in cold fusion.
Beside the synthesis, other aspects may be interesting to study as the structure of super-heavy nuclei. We have obtained very interesting results at GANIL with the LISE device. There are still a lot of things to do in prompt spectroscopy around the target as well as in delayed spectroscopy in the focal plane. This latter domain will gain, to my opinion, with this new generation of very high intensity beams. We will then be able to perform the spectroscopy of nuclei as heavy as hassium (Z=108).
In our group, we actually choose an original approach, that is not the approach to study the evaporation residues, i.e. the super-heavy nuclei themselves, but better to study the compound nucleus that exists before the neutron evaporation, before the cooling, and that undergoes fission most of the time. The advantage is that the cross section of the compound nucleus formation is much higher that the one of the evaporation residue. We can thus obtain important information about the localization of the expected island of stability. This allows us to go towards very heavy nuclei as the N=124 with high cross-sections and weak intensities. That is not conceivable today for the synthesis of super-heavy nuclei, strictly speaking.
The next step for the synthesis will be the new machines as SPIRAL2 that will allow a new impulse, except if we really get surprises with other channels. These could be options that have already been studied in the past, as massive transfers of nucleons from very heavy nuclei. But, either through very high intensity beams or through these new reactions, the SHE domain is a very big challenge in matter of experimental set-up and we keep working on it steadily.
More info:
Antoine Drouart's talk
Antoine Drouart's e-mail
Heavy and superheavy elements session
Words collected by K. Turzó at the XVe Colloque GANIL, Giens, France, from May 29th to June 2nd, 2006.
Beside the synthesis, other aspects may be interesting to study as the structure of super-heavy nuclei. We have obtained very interesting results at GANIL with the LISE device. There are still a lot of things to do in prompt spectroscopy around the target as well as in delayed spectroscopy in the focal plane. This latter domain will gain, to my opinion, with this new generation of very high intensity beams. We will then be able to perform the spectroscopy of nuclei as heavy as hassium (Z=108).
In our group, we actually choose an original approach, that is not the approach to study the evaporation residues, i.e. the super-heavy nuclei themselves, but better to study the compound nucleus that exists before the neutron evaporation, before the cooling, and that undergoes fission most of the time. The advantage is that the cross section of the compound nucleus formation is much higher that the one of the evaporation residue. We can thus obtain important information about the localization of the expected island of stability. This allows us to go towards very heavy nuclei as the N=124 with high cross-sections and weak intensities. That is not conceivable today for the synthesis of super-heavy nuclei, strictly speaking.
The next step for the synthesis will be the new machines as SPIRAL2 that will allow a new impulse, except if we really get surprises with other channels. These could be options that have already been studied in the past, as massive transfers of nucleons from very heavy nuclei. But, either through very high intensity beams or through these new reactions, the SHE domain is a very big challenge in matter of experimental set-up and we keep working on it steadily.
More info:
Antoine Drouart's talk
Antoine Drouart's e-mail
Heavy and superheavy elements session
Words collected by K. Turzó at the XVe Colloque GANIL, Giens, France, from May 29th to June 2nd, 2006.
