Seminar by Pablo de Vera

Tomorrow we will be hosting a seminar by Pablo de Vera from the MBN Research Center, Frankfurt am Main. Everybody is welcome!

Title: Combining Electron Transport Models and Atomistic Simulations: Modelling Radiation Biodamage and Nanofabrication Techniques
Date: June 20th
Time: 13.15
Where: U25A at SDU, Odense

Abstract:
The interaction of energetic charged particles, such as ion or electron beams, with condensed phase materials (organic and inorganic) finds many applications in fields as diverse as cancer therapy and nanofabrication. The same theoretical approaches can be used to model these different problems, provided that appropriate interaction probabilities between charged particles and the target materials are known. Furthermore, very frequently the same quantities have to be evaluated in order to assess the efficiency of either radiation therapy or nanofabrication techniques. For example, the level of concentration of the radial dose around the primary beam (due to the deviation of primary particles from their initial trajectory or the generation of secondary particles, usually secondary electrons) is very relevant in both applications. In cancer therapy, a larger concentration of the radial dose in the nanoscale produces more complex DNA damage, resulting in larger cell killing probabilities. In nanofabrication, it is desired that the radial dose is as narrow as possible, in order to fabricate structures (by degradation of materials deposited on a substrate) with the largest possible resolutions.

The propagation of radiation in the condensed phase and the effects the energy deposited in it produces can be modelled with different theoretical approaches. Charged particle transport is usually studied by Monte Carlo track-structure codes, although in some situations it is possible to solve this problem analytically, for example using diffusion equations. However, the description of the radiation effects in the materials usually needs models capable of providing details on the atomic and molecular scale, so molecular dynamics or molecular mechanics approaches are more convenient. Therefore, a comprehensive description of the energy deposition by radiation and of its effects on a condensed phase material requires an appropriate integration of both approaches.

In this seminar, recent results and ongoing work on the combination of radiation transport models and atomistic simulations will be described. In particular, two cases of practical interest will be discussed: i) energy deposition and effects around the paths of the energetic ions used in the advanced radiotherapy technique known as ion beam cancer therapy, and ii) the interaction of a focused electron beam with organic molecules deposited on a substrate, as used for the new nanofabrication technique known as focused electron beam induced deposition (FEBID).