Abstract
.We report on the development and characterization of the first radioactive boron beams produced by the isotope mass separation online (ISOL) technique at CERN-ISOLDE. Despite the long history of the ISOL technique which exploits thick targets, boron beams have up to now not been available. This is due to the low volatility of elemental boron and its high chemical reactivity which make the definition of an appropriate production target unit difficult. In addition, the short half-lives of all boron radioisotopes complicate tracer release studies. We report here on dedicated offline release studies by neutron capture and alpha detection done with implanted 10B in prospective target materials, as well as molecule formation and ionization tests, which suggested the use of multiwalled carbon nanotubes (CNT) as target material and injection of sulfur hexafluoride SF6 to promote volatile boron fluoride formation. Two target units equipped with an arc discharge electron impact ion source VADIS coupled to a water cooled transfer line to retain non-volatile elements and molecules were subsequently tested online. The measured yield of these first 8B ISOL beams increases in the series {}^{8}mathrm{BF}_{3} < {}^{8}mathrm{BF} < {}^{8}mathrm{B} < {}^{8}mathrm{BF}_{2}, reaching a maximum yield of 6.4 times 10^{4}8BF2+ ions per μC of protons.
Highlights
We report on the development and characterization of the first radioactive boron beams produced by the isotope mass separation online (ISOL) technique at CERN-ISOLDE
We report here on dedicated offline release studies by neutron capture and alpha detection done with implanted 10B in prospective target materials, as well as molecule formation and ionization tests, which suggested the use of multiwalled carbon nanotubes (CNT) as target material and injection of sulfur hexafluoride SF6 to promote volatile boron fluoride formation
In the case of boron these losses are so large, that no Radioactive Ion Beam (RIB) was produced by the ISOL method until now, many possibilities are offered by different combinations of targets and ion sources operated in facilities such as ISOLDE at CERN
Summary
We report on the development and characterization of the first radioactive boron beams produced by the isotope mass separation online (ISOL) technique at CERN-ISOLDE. Despite the long history of the ISOL technique which exploits thick targets, boron beams have up to now not been available This is due to the low volatility of elemental boron and its high chemical reactivity which make the definition of an appropriate production target unit difficult. In the case of boron these losses are so large, that no Radioactive Ion Beam (RIB) was produced by the ISOL method until now, many possibilities are offered by different combinations of targets and ion sources operated in facilities such as ISOLDE at CERN.
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