R&D status of pulse shape analysis for short-lived decay of superheavy elements in GARIS-II

Abstract

To search undiscovered superheavy elements, a series of commissioning experiments for the new gas-filled separator GARIS-II at RIKEN was recently carried out. A new data acquisition method was tested to study the short-lived α decay. Both the α decay and evaporation residues were detected by the silicon detectors, and the preamplified waveforms were then directly registered by a flash ADC and analyzed by means of a pulse shape analysis. This paper describes the identification of two sequential pulses (pileup events) from short-lived α decays and the determination of their energy and time difference by the template fitting method. The performance of the present system was evaluated by using a simulated data set and was successfully employed for online experimental data such as 220Ac → 216Fr.