Simulation of Anti-Compton Shield Augmentation to the Lundium Decay Station Using Geant4

Abstract

The Lundium decay station improves on the existing TASISpec spectrometer
used to investigate the nuclear structure of superheavy nuclei by photon- and
charged particle-spectroscopy. This thesis aims to explore the potential benefits
of the future Lundium station with the augmentation of anti-Compton shields com-
posed by a set of BGO scintillator bars. The effects of anti-Compton shields was in-
vestigated through a simulation toolkit, Geant4, developed by CERN. The Lundium
station augmented by the anti-Compton shields was constructed in the simulation
framework, then simulations of two point-like isotropic sources, 661.7 keV and Eu-
152, located at the Lundium focal plane were done. A beam-spot like Cs-137 was
also simulated. The data was sorted and analyzed considering the effects of Compton
scattering and the geometry of the setup. The response of Lundium and Lundium
with anti-Compton shields augmentation was compared using the 661.7 keV gamma
source. The effects of a more realistic situation were examined with the Cs-137
distribution, and the detector response of high energy gamma rays were explored
using Eu-152. The anti-Compton shield augmentation yielded peak-to-background
percentage increase of roughly 9% with comparable results in the more realistic
simulation with Cs-137 distribution. The use of anti-Compton shields with multiple
energies of photons was also successful in increasing the relative peak intensities.

Popular Abstract

Simulation to See Superheavy Elements

All matter as we understand are made up of combinations of different elements. The more common elements in the universe such as hydrogen and carbon are widely known and may feel familiar, but what about the rarest of the elements that are almost never seen? Elements are made up of 3 subatomic particles: neutrons, protons, and electrons. The stability of the isotopes, same element but with different numbers of neutrons, depends on the numbers and the ratios of these particles. Stability of an isotope mainly refers to its half-life, the average time it takes for half of an element’s sample to decay. The common and accessible elements (up to 103 protons), which are quite stable, have been studied thoroughly in their properties and potential applications. On the contrary, elements with more than 103 protons, commonly referred as superheavy elements, are more radioactive and thus unstable which generally make them rarer and difficult to deal with.
When the anatomy of an atom was understood and elements were found, there has been constant scientific effort to discover new elements. Recently, new superheavy elements (element 115 and 117) have been synthesized and confirmed by the scientific community. These elements were found in studies of the “Island of Stability,” a region hypothesized to exist in the superheavy region of the chart of nuclides where there is a temporary increase in stability due to effects of magic numbers in the nuclear shell model which describes the structure of atoms’ nuclei. While the stability tends to decrease with higher numbers of protons and neutrons, this island of stability represents abnormality in a trending group of increasingly unstable nuclei.
However, the formation of these new superheavy elements have been rare and difficult, which makes studying their properties even more challenging. In addition, due to the expenses and the energy required to create these elements, the experiments often involve multinational effort and equipment. Fortunately, these events can be simulated with statistically reliable accuracy. In addition, these experiments which involve superheavy nuclei, the number of relevant particles that can be detected is minuscule compared to experiments at other scales. By simulating the addition of anti-Compton shields which reduce unwanted detection, this thesis work can improve the performance of upcoming detector setups and even possibly the method of constructing detectors for other experiments, providing useful information for future work. By studying the characteristics of these rare elements, knowledge of elements in the superheavy region can be expanded which could lead to new possibilities for humans.

• author: Cho, Daesung
• supervisor: Luis Sarmiento
• organization: Nuclear physics; Department of Physics
• course: FYSK02 20191
• year: 2019
• type: M2 - Bachelor Degree
• subject: Physics and Astronomy
• keywords: Lundium, Geant4, Anti-Compton shield, gamma spectroscopy
• language: English
• id: 8984456
• date added to LUP: 2019-06-18 19:52:31
• date last changed: 2019-06-18 19:52:31