2015 Active Targets and TPC for Nuclear Physics Experiments Workshop

Exotic decay modes studied by means of the Warsaw Optical Time Projection Chamber

18 May 2015, 18:30

25m

Lecture Hall (National Superconducting Cyclotron Laboratory)

Oral Presentation Physics and Experiments Session 4

Speaker

Prof. Zenon Janas (Faculty of Physics, Uniwesity of Warsaw)

Description

The development of an Optical Time Projection Chamber (OTPC) at the University of Warsaw about a decade ago opened the possibility to investigate a broad range of rare decay modes with very high sensitivity. The detection of one decay event is sufficient to unambiguously identify the decay mode and establish its branching ratio. The detector is a TPC with amplification stage formed by a stack of GEM foils and optical readout consisting of a CCD camera and a photomultiplier tube (PMT). The images recorded by the CCD camera together with the time distribution of light collected in the PMT allow to reconstruct the trajectory of the decay products [1,2]. Such an approach is ideally suited to study the decay by (multi-) particle emission of very exotic isotopes. It was originally designed to obtain the first unambiguous proof of the two-proton (2p) decay of 45Fe and to study the angular correlations between the protons [3]. The same methodology and detection set-up was successfully applied also to measure the 2p decay of 48Ni [2,4], to discover the beta-delayed 3 proton (β3p) emission decay branch in 45Fe [5], and 43Cr [6] at the NSCL, and in 31Ar at GSI Darmstadt [7,8],. Moreover, it was applied to measure the energy distribution of beta-delayed deuterons from the decay of 6He at ISOLDE [9] and to study the beta-delayed tritium-alpha-neutron decay of 8He at the JINR in Dubna [10]. A review of the results and an outlook on future studies will be presented. [1] M. Ćwiok et al., IEEE Trans. Nucl. Sci. 52 (2005) 1895. [2] M. Pomorski et al., Phys. Rev. C 90, 014311 (2014). [3] K. Miernik et al., Phys. Rev. Lett 99 (2007) 192501. [4] M. Pomorski et al., Phys. Rev. C 83 (2011) 061303(R). [5] K. Miernik et al., Phys. Rev. C 76 (2007) 041304(R). [6] M. Pomorski et al., Phys. Rev. C 83 (2011) 014306. [7] M. Pfützner et al., GSI-SR2012-PHN-ENNA-EXP-17, GSI Report 2013-1 (2012). [8] A. Lis et al., in preparation. [9] S. Mianowski et al., in preparation. [10] M. Pfützner et al., in preparation.