PhD defence Andrea Marchese: Electron cyclotron resonance in plasmas using intense THz radiation

Date of news: 23 February 2022

Monday 28 February, dr. Andrea Marchese successfully defended his thesis on Electron cyclotron resonance in plasmas using intense THz radiation. His research was centred around the free-electron lasers and high field magnets of HFML-FELIX.

His main task was to develop an experimental setup that enables researchers to use the combination of these superpowers. As it was mostly pioneering, Marchese encountered several unexpected difficulties. One of them was that Helium gas, used to cool the samples, can induce a plasma breakdown when exposed to intense THz light and strong magnetic fields. This strongly disturbs the experiments. Marchese studied when, how and how fast the plasma is formed and characterized exactly what happens under which circumstances. The results of this explorative study are essential for researchers when they are building a research setup that combines free-electron lasers and high magnetic fields. It also gives fundamental insights in the life time of an electron and the interaction of electrons with the surroundings.

Photo: Truus Stevens

Dr. Marchese receives his doctorate from prof. Peter Christianen

Another part of the thesis focused on extending the fundamental knowledge of a type of semiconductor by several experiments, exposing it to extreme conditions like strong magnetic fields, intense THz radiation, low temperatures and high pressure. Using these tools, Marchese studied the time dynamics of the electron in the semiconductor. The intense THz radiation was used to excite the electrons to energies that could be controlled by tuning the magnetic fields. Then, the variation in the transmitted THz light through the semiconductor was used to reconstruct for how long the electrons remain excited. These times depend on how the electron energy is related to the energy of the semiconductor lattice vibration.

Marchese studied Physics in Rome. His Master Internship focused on materials exposed to high magnetic fields and THz radiation. He was eager to continue in this field of research and as HFML-FELIX is one of the few large scale research infrastructures world-wide that offer the combination, he decided to do his PhD in Nijmegen. Coming from Rome, he was a bit worried that Nijmegen was too small for him, but he soon discovered that the cultural (night) life was not so bad. He spent a lot of time in the lab, but was for example also part of an international theatre group. Marchese: “We even performed across the border in Kleve, so I can now call myself an international researcher ánd an international actor, haha.”

thesis cover Andrea

If you are a music lover, the cover of Marchese’s thesis might look familiar; it resembles the cover of the album ‘London Calling’ from The Clash, but then, if you look closely, in a laboratory setting. Marchese: “It reflects the enormous power we can generate at the laboratory but also shows the frustration I sometimes experienced.”

Marchese started with a postdoc at the Dynamic Optical Systems Lab, University of Barcelona, where is working on the development of an ultrafast microscope.

The defence took place on Monday 28 February
Promotor: prof. dr. P.C.M. Christianen
Co-promotor:  dr. H. Engelkamp