Nuclear spectroscopy with Geant4

Abstract

Abstract. The simulation toolkit Geant4 was originally developed at CERN for high-energy physics. Over the years it has been established as a swiss army knife not only in particle physics but it has seen an accelerated expansion towards nuclear physics and more recently to medical imaging and -and ion-therapy to mention but a handful of new applications.The validity of Geant4 is vast and large across many particles, ions, materials, and physical processes with typically various different models to choose from. Unfortunately, atomic nuclei with atomic number Z > 100 are not properly supported. This is likely due to the rather novelty of the field, its comparably small user base, and scarce evaluated experimental data.To circumvent this situation different workarounds have been used over the years. In this work the simulation toolkit Geant4 will be introduced with its different components and the effort to bring the software to the heavy and superheavy region will be described.

Gamma and conversion electron spectroscopy using GABRIELA

“…To bypass this limitation different methods are used: one approach is to hard-code the whole atomic relaxation process as a part of the Primary Generator Action of Geant4, while another method consists of disguising heavy nuclei as lighter ones (i.e. heaviest element available in Geant4) by modifying their atomic properties [21,22]. In this study, modifications in the Geant4 source code were introduced to allow atomic relaxation processes up to Rf and the Auger and fluorescence data sets were extended up to Z = 104 by extrapolating the existing data in the range 90 ≤ Z ≤ 100 using polynomial functions.…”

Results and plans for nuclear spectroscopy of superheavy nuclei: the Lund perspective

“…Simulations -or virtual experiments -using the Geant4 toolkit have entered the nuclear physics domain some time ago. Therefore, TASISpec has been coded in detail in Geant4 [31] while allowing for adoptions in geometry and detector types for a given TASISpec set-up, for instance, for the 'ele-ment 115 experiment' [32,33]. It is also possible to conduct virtual Geant4 experiments in 'real time' and compare virtual Geant4 data with data taken in real experiments.…”

“…This feature has proven very helpful for experiments in which TASISpec had been placed behind ion traps, such that the decay of a certain isotope with a given mass, i.e., the decay of a selected single quantum state, could be followed over time [34] -regardless whether that be α decay, β decay, or proton emission [35][36][37]. The most important asset of the Geant4 simulations for superheavy element spectroscopy studies, however, is the capability of self-consistency control of the decay schemes derived from the measured α, electron, and photon spectra, as well as coincidences among these (see, e.g., [32,33] and below). Using the decay schemes as physics input for Geant4, virtual experiments provide expected spectra, which within given statistical limits must match the observed ones in order to validate the very same suggested decay scheme.…”

“…Supported by dedicated Geant4 simulations [31][32][33], it is possible to probe, study, and suggest various decay schemes along the 288 Mc chain. For the first two steps, 288 Mc→ 284 Nh and 284 Mc→ 280 Rg, hardly any α-photon coincidence was observed [63,68].…”