Welcome to the CHARMS See – Tea Saturday, March 05, 2016 Comparison of ISOLDE yields with calculated in- target production rates Strahinja Lukić,

Release of the Light Alkalis From ISOLDE Targets 2 Outline Release of nuclides from ISOLDE targets In-target production rates Dependence of the overall efficiency on the isotopic half-life

Release of the Light Alkalis From ISOLDE Targets 3 Release of Nuclides from ISOLDE Targets Nuclide production Thermal diffusion Effusion Ionization Extraction by 60 kV field Losses to chemical reactions, leaks, radioactive decay... Proton beam

Release of the Light Alkalis From ISOLDE Targets 4 Typical ISOLDE Target 20 cm

Release of the Light Alkalis From ISOLDE Targets 5 In-target production In-target production rates estimated taking into account:  Attenuation of the beam along the target due to nuclear reactions  Energy loss due to electromagnetic interactions and the resulting change in the production cross-sections along the target  Low-energy fission induced by secondary neutrons in fissile targets

Release of the Light Alkalis From ISOLDE Targets 6 Importance of the secondary reactions in the thick target Comparison of the total in-target production (ISOLDE, EURISOL report) with calculated in-target primary production rates in UC x target (50 g/cm 2, 20 cm depth, 1.4 cm diameter) Difference almost entirely due to low-energy fission induced by neutrons 40% of incident protons undergo a nuclear reaction Roughly 6 secondary neutrons per primary proton (in primary reactions) About 0.7% of the produced neutrons get captured by uranium

Release of the Light Alkalis From ISOLDE Targets 7 Correlation of ISOL yields with isotope half-life Comparison of ISOLDE-SC yields † to in-target production rates Ratio yield/produced → overall extraction efficiency for the nuclide. For a given element – target – ion source, the efficiency is correlated with the isotope half-life † H.-J. Kluge, Isolde users guide, CERN, Geneva, 1986, web: Same general behavior found in many cases.

Release of the Light Alkalis From ISOLDE Targets 8 Examples

Release of the Light Alkalis From ISOLDE Targets 9 Alkalis Very easy to ionize by surface ionization, simple chemistry, volatile When ionized, electronic configuration of a noble gas High efficiencies – ε s often 100% Fast release – t 0 of the order of seconds

Release of the Light Alkalis From ISOLDE Targets 10 Alkaline earths Surface ionization Chemical separation from alkalis using fluoride gas leak, to form XF + molecular ions ε s several % t 0 of the order of tens of seconds

Release of the Light Alkalis From ISOLDE Targets 11 Halogens Negative ionization – difficult ε s several % t 0 of the order of tens to hundreds of seconds

Release of the Light Alkalis From ISOLDE Targets 12 Noble gases Plasma ionization Chemical separation by condensation of the impurities in the transfer line Fast release

Release of the Light Alkalis From ISOLDE Targets 13 Cases that "didn't work"

Release of the Light Alkalis From ISOLDE Targets 14 Conclusions Quantification of the essential properties of the overall ISOL efficiencies Practical  ε s is the important information  behavior with short half-lives indicates where to put the development efforts General in scope - applicable across the entire table of elements and for all target and ion- source systems