Jan Benedikt’s Interview to The Science and Engineering Cafe’

Read the much anticipated interview of our new Scientist of the Week, Dr. Jan Benedikt. Jan talks about his new position, describes his latest research and the recent ISPC conference.

Jan also offers a few tips on how to motivate new scientists by showing them the “big picture”.

I hope you enjoy the interview as much as I did!


Daphne Pappas

Three versions of rf-atmospheric pressure plasma jets for separation of plasma generated photons and reactive species. For more see Schneider et al. J. Phys. D 48 (2015) 444001.


Jan Benedikt’s Interview


1) What is your personal motto?

My personal motto is a quote from Antoine de Saint-Exupéry: “If you want to build a ship, don’t drum up people to collect wood and don’t assign them tasks and work, but rather teach them to long for the endless immensity of the sea.” Motivated people with open mind that are ready to work hard are a blessing for a research lab, and I have always enjoyed working with such colleagues. That is why I am trying to motivate the young people around me by showing them the “endless immensity” of nature’s beauty, sometimes realized even in simple phenomena around us.

2) Which is your favorite conference and why?

My favorite conference is the bi-annual Plasma Processing Science (PPS), one of the Gordon Research Conferences (GRC). This relatively small conference consists of only one session on pre-selected session discussion topics, and the extended time for these discussions is very stimulating. Additionally, its open format allows the attendees to get to know each other personally and provides young researchers the ability to network with known experts in the field. I have been attending this conference since 2002 when I was just a Ph.D. student, and I hope I will be able to continue attending it because I have always learned new ideas and met very interesting new people. I am therefore recommending all followers of the Science and Engineering to visit the next PPS, which will be held on 5-10 August 2018, at Smithfield, RI, USA. Link: https://www.grc.org/programs.aspx?id=12575

3) You recently transitioned to a new position. Please tell us about your new role, will you continue your research on the same topics?

I have successfully applied for a full professor position at the Christian-Albrechts-University in Kiel, Germany, and I started this position in April this year. Kiel is close to Ruhr-University Bochum (RUB), another academic institution in Germany with strong low-temperature plasma science. My new colleagues have prepared an application to German Science Foundation (DFG) for a Collaborative Research Center (CRC) called The Plasma Interface. This planned research is a collaborative work of plasma physicists, surface physicists, solid-state physicists, chemists, and material researchers aiming at the full understanding of the plasma interactions with the surrounding surfaces and unifying of the theoretical description of this interface. I am very happy to be part of it now. We have just put a tough reviewing procedure behind us, and we are expecting the (hopefully positive) funding decision at the end of November of this year. A successful decision would bring me back to the diagnostics of low-pressure non-equilibrium plasmas, the topic of my Ph.D. thesis and research activity that I have learned a lot from my colleagues during my time at RUB. This work should fill roughly half of my future research time. But I will also stay active in the field of diagnostic of atmospheric non-equilibrium plasmas and the development and characterization of atmospheric non-equilibrium plasma sources, mainly for material synthesis and surface treatment. Research on atmospheric plasmas will fill, therefore, the second half of my research time.

4) I will not be able to attend the ISPC this year. I am sure that it will be a huge success, Dr. Sylvain Coulombe one of the chairs of the conference was featured on the Science and Engineering Café last year and was very excited about the conference.

The title of your invited talk at this conference is “Cold atmospheric plasmas as a source of reactivity in plasma-substrate interaction studies,” can you provide a summary of the talk for those who will not attend the conference?

The ISPC conference is another excellent conference, and I enjoyed it very much this year. In my talk, I have summarized activities of my group in the fields of diagnostics of atmospheric plasmas and characterization of the interaction of different plasma components (reactive radicals, photons, ions, or electric fields) with biological substrates such as biomolecules, bacteria, and cells. With a clever design of the plasma jet, we can separate the reactive species from photons. This design allows us not only to study the individual and combined effect of these components on -for example- bacteria but also to measure vacuum-UV spectra in the 50 nm to 300 nm range. The new highlight is an ion source utilizing photoionization through the plasma-generated vacuum-UV photons, which can study the isolated effect of ions on a variety of substrates. I have also shown how you can use these plasma sources to study the interaction of some selected radicals such as O or N atoms or ozone molecules with substrates or even liquids. We could, for example, demonstrate that an atmospheric non-equilibrium plasma in a dry He/O2 gas mixture is a very effective source of solvated O atoms. My main message of this talk was that these plasma sources could become an alternative to some UHV beam sources used in the interactions studies of reactive species, ions, or photons with surfaces.

5) A lot of your recent research is focusing on the application of plasma (gas) phase diagnostics. Given that the reactors are open air systems of unique geometry (for example DBDs are generated in interelectrode gaps of only a few mm) and that the electron mean free path is extremely small, what are the challenges associated with the application of OES, mass spectrometry, etc.?

Many people in the field have shown that the challenging task of atmospheric plasma diagnostics can be accomplished and provide a plethora of quantitative experimental data with high spatial and temporal resolution. All these experiments have to be performed with extreme care, taking into account the effect resulting from the high collision rates, small dimensions, and different plasma chemistry (three- body collisions). The main challenge remains, therefore, to work carefully and to invest the time, money, and energy into building the diagnostics and analyzing the obtained data, more often than ever with the necessary support form plasma simulations. My favorite diagnostic is molecular beam mass spectrometry (MBMS). It can be used for the analysis of ions and reactive and stable neutral species in the gas mixture originating from the atmospheric plasma directly or from the plasma effluent. We are able now to measure radicals with densities below 10^14 cm-3 and even estimate the absolute ion densities. But it took two Ph.Ds. to obtain the best design of the gas sampling and molecular beam chopping system and involved simulation of plasma chemistry, isentropic supersonic expansion of the gas mixture, Monte Carlo simulation of the transition of the molecular beam into the molecular flow, and the simulation of ion trajectories in the mass spectrometer to come to this point. The MBMS is not a very popular diagnostic method, probably because you have to be extremely careful with the design of your experimental setup and the data analysis. But I can say from my own experience that it is worth the effort, and I hope that my example will motivate other people to long for the endless immensity of our plasma research sea.


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