Welcome to the CHARMS See – Tea Sunday, October 11, 2015 Release of Light Alkalis (Li, Na, K) From ISOLDE Targets Strahinja Lukić,

Release of the Light Alkalis From ISOLDE Targets 2 Outline Release of nuclides from ISOLDE targets Release measurement technique Results

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 Ion-Sources Surface  Hot transfer line made of a metal with high work function (W, Ta) Plasma  Electron beam ionizing a gas mixture (Ar+Xe)  Hot or cold transfer line Laser  excitation and ionization using characteristic wavelengths in 2-3 steps  Chemical selectivity Surface Ion-Source EXTRACTION ELECTRODE

Release of the Light Alkalis From ISOLDE Targets 6 ISOLDE Facility Layout Transmission Losses

Release of the Light Alkalis From ISOLDE Targets 7 Release Measurement Using the Tape Station Proton beam pulses are spaced by s Ion beam implanted on a tape at a certain time after the p + bunch  Timing and duration controlled by a deflector magnet Tape carries the ions to the detector (1s) Detection of β, α, γ or n during a specified time Detector

Release of the Light Alkalis From ISOLDE Targets 8 The Release Curve

Release of the Light Alkalis From ISOLDE Targets 9 Yield and In-Target Rates The release curve is established for a long lived isotope and applied to the shorter lived isotopes of the same element The decay losses can be deduced and in-target production rates calculated But, losses to leaks and chemical reactions impossible to estimate → yields are not always reproducible

Release of the Light Alkalis From ISOLDE Targets 10 Cross-sections Production cross-sections can be estimated assuming that:  All the nuclides are produced in primary reactions (approximately correct for Li, Na and K)  Production cross-sections are constant along the target despite the proton energy loss (approximately correct for 1 GeV protons ? Energy loss ~50 MeV, xs variation ~20-30% ?)

Release of the Light Alkalis From ISOLDE Targets 11 Some Results Order of magnitude good except data from specific targets Shape of the distribution approximately good (steeper than in ABRABLA results)

Release of the Light Alkalis From ISOLDE Targets 12 Some Results Very few data, incompletely documented Order of magnitude good Shape of the distribution approximately good

Release of the Light Alkalis From ISOLDE Targets 13 Other Results - K Too few data for potassium in the segment that was treated Order of magnitude good except in the same specific targets as for sodium

Release of the Light Alkalis From ISOLDE Targets 14 Other Results - Li Very difficult element for ISOL  Small atom - leaks through solid materials  Fast diffusion – faster than the measurement system?  No sufficiently long-lived isotope – difficult to establish the release curve.  Extrapolate the release curve parameters from K and Na?

Release of the Light Alkalis From ISOLDE Targets 15 Other Results - Li Estimated release curves extremely long (not logical for Li) → apparently high decay losses → high xs Using parameters extrapolated from sodium doesn't seem to work Possible errors because of the time-dependent background (He) 8 Li produced in U-Carbide

Release of the Light Alkalis From ISOLDE Targets 16 Other Results - Li No experimental data to compare to.

Release of the Light Alkalis From ISOLDE Targets 17 Conclusions The method seems to work although it would be difficult to use it for independent cross-section measurements. The main problem - unpredictable losses Yield data are scarce, at least in the period that was treated (1993 – 2002) Systematic measurement of the time-dependent background could help, particularly for lithium