Danielius Lingis, a physicist at the Department of Nuclear Research of FTMC, has become a PhD. He defended his thesis "Numerical Simulation of the Light Ion Backscattering Spectra in the Particle Channeling Geometry" (academic supervisor: Dr. Vitalij Kovalevskij, scientific advisor: Dr. Artūras Plukis).
Congratulations to our colleague, and good luck with your important work!
Danielius has developed an open-source numerical model - a computer program that can be freely modified and rewritten by any user who knows how to program. This allows the simulation (study using computer models) of the backscattering spectra of light ions in crystalline materials. How to understand this?
One way to determine the composition and other properties of crystalline materials is to use a particle accelerator, where tiny ions are rapidly released into the sample. The particles then bounce back (at an angle between 90° and 180°), which is called backscattering.
"We detect the original particle and estimate how much energy it lost in the process. The spectrum and energy of the returning particles are recorded, and then the composition or other properties of the material can be determined," says Lingis.
(Particle accelerator at FTMC Department of Nuclear Research. Photo: D. Lingis)
A computer program developed by FTMC physicist facilitates such experiments in two ways. The first is that, if the scientists do not know any of the properties of the sample (the material being studied) at the start, they record an experimental spectrum of light ions using a particle accelerator, detectors and other equipment. This is then replicated in the software to see if the two experiments match.
In the second case, if physicists have at least some information about the material they are studying, an initial computer simulation can give an indication of what to expect from a real experiment in a particle accelerator.
"The thesis developed an open-source model to simulate the backscattering spectra of light ions from amorphous materials, as well as a modification/improvement of the original numerical model for particle channeling in crystalline materials," says Danielius.
Particle channeling occurs when crystalline materials have open channels in certain directions due to the orderly structure of the atoms; ions move in the centre of the channel, where atoms are absent in an ideal crystal lattice. This 'void' focuses the light ion particle in the centre of the channel and allows it to propagate more freely and penetrate deeper into the material compared to amorphous materials. This reduces, among other things, the energy loss of the particle.
"The open-source features of the model allow users to freely modify the numerical simulation conditions - using different libraries of particle scattering cross-sections, as well as libraries of particle energy losses - and to freely modify the physical processes, allowing them to numerically simulate exactly what the user wants," he stresses.
These experiments are extremely complex, so tools such as dedicated computer programs are essential, says D. Lingis: "There are several open-source and freely available tools on the market that allow such analyses on amorphous samples. However, closed-source commercial tools dominate.
When experiments are carried out on crystalline materials, there is often a further process involved in the interaction of particles with the material that complicates both the modelling of particle interactions and the interpretation of backscattering spectra. A number of tools are available for numerical modelling of backscattering spectra from crystalline materials, but only a few of them are open source.
It is the open source tools, while freely available and relatively easy to modify, that are old and no longer supported. So the work has led to the development of a freely available and freely modifiable model based on the continuously updated GEANT4 physics numerical modelling package."
Therefore, Daniel says, the development of a free and openly available computer program will make it easier for colleagues from Lithuania and abroad to study physical processes and test their hypotheses: "A week ago, a young scientist from Canada wrote to me personally complaining about the lack of open source tools. Once we have clarified his problem, it is likely that he will now use my tool with his modifications. So there is already interest from the scientific community."