ISOLDE Seminar

Channeling effect in ultra-thin monolithic silicon telescopes

by Fredrik Parnefjord Gustafsson (KU Leuven)

508 (CERN)




Determining the cross section of the 8Li( alpha,n)11B reaction in the low energy regime Ecm < 2 MeV has been of particular interest in recent decades. In a potential inhomogenous Big Bang scenario this reaction could bridge the mass gap at A = 8 leading to the evolution of heavier nuclei in the very early universe. Furthermore, full network calculations indicate that this reaction could play a vital role in enhancing the r-process nucleosynthesis in supernovae. A new method has been proposed at Nishina Center, RIKEN to study the low energy resonances using DE-E Monolithic Silicon Telescopes (MSTs). Each telescope consists of five ultra-thin 1 µm (DE) silicon detector pads on a 500 µm (E) silicon detector. To assure optimal detector performance it is crucial to determine the detector characteristics and response for particles incoming at different angles. Ultra-thin silicon detectors are particularly prone to the channeling effect which degrade the detector signal for incident particles along the crystal planes. A Pelletron tandem accelerator was used to investigate the signal characteristics at varying angle of incidence.  Based on this investigation Important detector characteristics could be deduced, such as the optimal detector orientation and particle detection threshold. The experiments show promising results that guide the construction of a monolithic silicon telescope array that could be used to investigate the low energy resonances of this reaction.

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