Sub-microsecond alpha particle emitters

  • Anton Såmark-Roth (Roll ej angiven)

Aktivitet: Föredrag eller presentationPresentation


Above nuclear shell closures, fast α-decaying nuclei with half-lives down to tens of nanoseconds exist. Due to their short lifetimes, it has been difficult to measure their spectroscopic properties in detail as α-decays pile up in former analogue electronics experimental set-ups. For the superheavy element 115 experiment, conducted in 2012 at GSI TASCA [1, 2], fast sampling ADCs were used. This enables extraction of energies and times of pile-ups with tailor-made algorithms, and moreover, allows to correlate coincident photons, i.e. x rays or γ rays, to the individual α-decay steps. This coincidence information is crucial for any subsequent nuclear structure interpretation.

A pile-up trace analysis routine has been developed [3]. For instance from correlation plots displayed in Figure 1, a connection to the tabulated α-decay chain of Ra-219 to Rn-215 could be firmly established. In fact, multi-nucleon transfer reaction channels, which form the main background in the E115 experiment, populate the whole region of fast α-emitters “North-East” of 208Pb.

This region of sub-microsecond α-particle emitters has been thoroughly studied with the new type of data. The analysis takes off from a close examination of the α1-α2 correlation 2D-spectrum in conjunction with half lives and coincident γ rays. The results cover half-lives, decay modes and branching ratios of these short-lived nuclei which have in some cases not been studied since the 1970s. The obtained data is compared with large-scale nuclear shell-model calculations and contemporary α-decay models developed in Lund [4].

[1] D. Rudolph et al. Spectroscopy of Element 115 Decay Chains. Phys. Rev. Lett. 111, 112502. 2013.
[2] Ulrika Forsberg. Element 115. PhD thesis, Faculty of Science, Lund University, 2016.
[3] Anton Roth. Extraction of energy and time from pile-up pulses with fast sampling ADC analysis techniques. Master thesis, Faculty of Engineering, Lund University, 2016.
Period2017 okt. 10
Evenemangstitel9th Workshop on the Chemistry of the Heaviest Elements
Typ av evenemangKonferens
PlatsAscona, Schweiz

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