News

Conferences

Presentations on Methane Pyrolysis and HiPIMS at PSE 2022

Simon Kreuznacht and Achim von Keudell presented their lectures on "Methane Pyrolysis" and "HiPIMS - a diagnostic challenge" at the plasma surface engineering (PSE) conference in Erfurt. This conference with 550 attendees focus on applications of plasma technology for material processing and modification. 

Conference report

Gordon research conference

From July 23rd to July 29th the Gordon Research Conference and Seminar on Plasma Processing and Science was held in Andover, New Hampshire. The conference focused on plasmas and their interactions with matter while the seminar focused on investigating multiphase and multiscale plasma-material interactions. The research of EP2 was presented by Judith Golda, Rahel Buschhaus and Simon Kreuznacht. Judith Golda had a talk on "State enhanced actinometry in atmospheric pressure discharges". Rahel Buschhaus presented her work on "Ion-induced secondary electron emission of metal surfaces analysed in beam experiments". Furthermore, four poster presentations were given by this group.

Awards

Rahel Buschhaus from SFB TR 87 project C7 wins a poster prize at DPG conference 2022

Rahel Buschhaus won the poster prize in the category 'Phd students in low-temperature plasma physics'. During the annual DPG spring meeting, she presented a poster entitled 'Ion-induced secondary electron emission of metal surfaces analyzed in an ion beam experiment'.

Publications

Achim von Keudell new Editor in Chief for Plasma Processes and Polymers

Achim von Keudell became with the beginning of March one of the four Editors in Chief of Plasma Processes and Polymers

Awards

Dissertation Award of the Faculty of Physics and Astronomy for Dr. Katharina Grosse.

The generation of plasmas in liquids is important for applications such as electrolysis, water purification or medicine, but also opens up a number of very fundamental questions. These plasmas are generated by short voltage pulses in the range of many kilovolts and a few nanoseconds in duration applied to a tungsten tip submerged in water. There is a lively debate around understanding the ignition of these plasmas, as electron multiplication during plasma ignition is postulated to occur either within small nanovoids, small fractures in the water, or as an electron avalanche in the water itself. In both cases, field emission at interfaces or field ionization of water molecules plays a crucial role. Dr. Grosse studied the whole dynamics of these plasmas from ignition to afterglow using time-resolved emission spectroscopy and compared it with modeling of emission and fluid dynamics. It showed that the broad continuum is produced by blackbody radiation, with a temperature of 7000 K, exactly equal to that of boiling tungsten. Electron densities of several 1025 m-3 can be derived from the strong broadening of the Balmer lines of the hydrogen atoms. Furthermore, a strong self-absorption of light from the region of the plasma channel is observed while light from the running ionization front shows no self-absorption. From this it can be deduced that the plasma runs directly through water and is not formed within nanovoids. Thus, field emission and field ionization dominate. After this first plasma pulse, the high power density leads to the phase transition from water to water vapor and bubble formation within the first microsecond. The high pressure in the range of GPa causes an expansion of the cavitation bubble and the generation of a sound wave propagating in the liquid. This could be directly observed using shadowgraphs. In particular, the speed of sound reaches several 1000 meters per second, indicating the very high pressure at the beginning of the discharge. Based on this measurement, Dr. Grosse has very significantly extended the understanding of these plasmas.

Funding

DFG approves second funding period of the CRC 1316

Plasmas for the Systems for material conversion are an important component in the utilization and storage of decentrally generated renewable energies. The Collaborative Research Center 1316 (CRC 1316) "Transient Atmospheric Pressure Plasmas - from Plasma to Liquids to Solids" is dedicated to combining atmospheric pressure plasmas with catalysis to develop the most flexible solutions possible for this material conversion. "They should be scalable, controllable and robust against external influences, such as impurities in the starting materials," explains Prof. Dr. Achim von Keudell, spokesman of the CRC.

The first funding period of the CRC 1316 was dedicated to the elucidation of transient phenomena in atmospheric pressure plasmas as well as interfacial processes at the surface of catalysts. Here, the focus was on three systems: the plasma-catalytic conversion of gases, the combination of plasmas with electrolysis at the interface between liquid and solid, and plasma-assisted biocatalysis, in which enzymes very selectively produce new molecules. The researchers were able to make great progress in these areas: For example, they achieved precise control of the formation of reactive particles in these plasmas. They were also able to gain a deeper understanding of the atomic and molecular surface processes in these systems.

In the second funding period, these findings will be brought together to make the best possible use of the interplay between a plasma with its reactive particles and a catalytically active surface. There are many further questions in this regard, since in traditional catalysis, for example, stable molecules are essentially reaction partners, whereas in plasma catalysis, reactive particles or highly excited species can accelerate or suppress a specific reaction path. On this basis, the first prototype plants for plasma catalysis, plasma electrolysis and plasma biocatalysis are to be developed.

In addition to the RUB as the host university, researchers from the University of Ulm, the Jülich Research Center and the Fritz Haber Institute in Berlin are involved in the CRC.

Funded Workshop

Hereaus Seminar in "Non-thermal plasmas for sustainable chemistry" on April 23-27, 2023

The Herause Foundation just funded a workshop on Non-thermal plasmas for sustainable chemistry organized by Yiguang Ju (Princeton), Tomohiro Nozaki (Tokyo Inst. technol.), Annemie Bogaerts (univ. Antwerp), and Achim von Keudell (RUB) to be held in Bad Honnef in April 2023.

Teaching

Hands-on Writing course

On 11st June, 18 EP2 members, students, PhDs, and PostDocs, participated in an online hands-on writing workshop provided by A. von Keudell. During the day, we learned language and structure tips and tricks for clearly delivering our research results and messages. We applied what we have learned directly by writing our own texts and based on them discussed typical mistakes. All in all, it was a motivating and fruitful workshop day.

Teaching

 

Mikroplasma-Versuch Online

 

Der Praktikums-Versuch 401 "Mikroplasmen" wurde jetzt so weit überarbeitet, dass er weitgehend selbständig Online durchgeführt werden kann.

Steuerung des Onlineversuchs Mikroplasmen

Der Versuch erlaubt die emissionspektroskopische Untersuchung eines Atmosphärendruck-  Mikroplasmajets. Dabei wird per Frensteuerung sowohl die Entladung bedient und überwacht, als auch Spannung und Strom aufgenommen. Schrittmotoren erlauben eine Positionierung einer Lichtfaser im Bezug zum Entladungskanal. Die Spektren eines damit gekoppelten Spektrographs werden aufgenommen und können anschließend ausgewertet werden.