Fusion and the Discovery of Isotopes

M Thoennessen,E.C Simpson,I.P Carter,C Simenel,K.J Cook

doi:10.1051/epjconf/201716300060

Abstract

Heavy-ion fusion-evaporation has been the most productive method to form and identify new isotopes. Of the presently known over 3200 isotopes, almost 25% were discovered with heavy-ion induced reactions. Since the development of the first heavy-ion beam at Berkeley in 1950 most of the nuclides on the neutron-deficient side of the line of stability and all isotopes of the superheavy elements were discovered utilizing fusion reactions. In addition, some isotopes were first produced in heavy-ion transfer, charge-exchange, incomplete fusion or deep inelastic reactions. The discovery of isotopes relies on new advances in accelerator and detector technology. The continuous development of pioneering and innovative separation and detection techniques have pushed the limit towards ‒ and in many cases beyond ‒ the proton-dripline. A review of the discovery of neutron-deficient and super-heavy nuclides in heavy-ion induced reactions as well as an outlook for the discovery potential in the future is presented.

Highlights

The discovery of new isotopes is the first and necessary step towards the study and exploration of more and more exotic nuclei
The compilation revealed that more than 25% of these isotopes were formed in heavy-ion induced fusion reactions making this method the most productive way to discover new isotopes
The current paper presents an overview of the discovery of neutron-deficient and super-heavy nuclides in heavy-ion induced reactions as well as an outlook for the discovery potential in the future

Summary

Heavy-Ion Accelerators

The discovery of new isotopes is the first and necessary step towards the study and exploration of more and more exotic nuclei. Luis Alvarez from the University of California at Berkeley described the acceleration of carbon ions: “The 37-inch cyclotron chamber was filled with CH4 and a beam of 50 Mev 6C12++++++ ions was detected with a linear amplifier To resolve these ions from alpha-particles, it was necessary to reduce the dee voltage and to adjust the magnetic field to the low side of the alpha-particle peak. Very small beams of these high speed particles were led from the cyclotron through a thin window into a Wilson cloud chamber of conventional design” [9] Another four years later, York et al presented further improvements at the APS meeting in Berkeley, July 12−13 1946: “Experiments have been done to produce accelerated stripped light nuclei with the 60” Berkeley cyclotron for use in nuclear experiments. Typical yields from an arc source are 1000 C12,+6 146-Mev ions per second and 100,000 C12,+6 135-Mev ions per second. . . ” [10]

Fusion Evaporation Reactions

Discovery potential

Findings

Summary