Energy-dependence of the non-Rutherford scattering of protons on C and Mg

The cross section (probability) of elastic scattering of certain projectiles at specific high energies on the atoms of a target deviates considerably from the Rutherford formula. This phenomenon is sometimes used to enhance the sensitivity to certain elements, as is needed for the advanced characterization of nanometer scale components. However, as you will show in this Master thesis project, it can also be exploited to improve calibrating the voltage of the accelerator.

Colaux et al. [1] pioneered a new method to calibrate the voltage of an accelerator by using the elastic non-Rutherford backscattering reaction 16O(α, α)16O resonance centered around 3038.1 keV. It relies on the fitting of an experimental spectrum via a simulation software to obtain a fitted energy which in theory represents the "true" energy of the beam. By comparing this energy to the one derived from the terminal voltage, the accelerator can be calibrated. This technique is accurate, but much quicker than more elaborate methods since the calibration can be carried out with a single measurement. However, the required energy is not attainable with many accelerators, and the used software is case-specific and not readily available.

We will investigate elastic non-Rutherford resonances other than 16O(α, α)16O at 3038.1 keV with the aim of calibrating the Van de Graaff accelerator in the Leuven ion-beam center (maximum voltage 2500 kV). We will study the resonances in the scattering cross section of protons on carbon and magnesium, as they are intense and hold great promise for this purpose [2]. The recorded non-Rutherford spectra will be analyzed with a new release of the Ruthelde software which allows the accelerator voltage as a free parameter [3].

You will investigate the applicability and attainable accuracy of the resonances for the voltage calibration. As such this study will establish a new method to calibrate the voltage of an electrostatic accelerator with can reach energies from 500 keV up to 2.5 MeV.

[1] J.L. Colaux, et al. “On the traceably accurate voltage calibration of electrostatic accelerators”. In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 349 (2015), pp. 173– 183.

[2] AF Gurbich. “SigmaCalc recent development and present status of the evaluated cross-sections for IBA”. In: Nuclear Instruments and Methods in Physics Research Section B 371 (2016), pp. 27–32.

[3] R. Heller, N. Klingner, N. Claessens, C. Merckling and J. Meersschaut, “Differential evolution optimization of Rutherford backscattering spectra”. In: Journal of Applied Physics 132 (2022) 16.

Master's degree: Master of Science

Required educational background: Physics, Nanoscience & Nanotechnology

University promotor: Stefan De Gendt (Chemistry, Nano)

For more information or application, please contact the supervising scientist Johan Meersschaut (johan.meersschaut@imec.be).

Imec allowance will be provided for students studying at a non-Belgian university.