Young Professionals introduces outstanding young professionals (under 40 years of age) who are doing interesting things in cryogenics and superconductivity and who show promise of making a difference in their fields. Debuted in the Summer 2006 issue, the feature has presented many young persons whom we are proud to see have indeed lived up to that promise.

Peter Cheetham, 28
My educational and professional background: I received my PhD in electrical engineering from the FAMU-FSU College of Engineering in 2017. Since then I have worked as a postdoctoral fellow at Florida State University’s Center for Advanced Power Systems (FSU-CAPS). Recently I was promoted to a research faculty position at FSU-CAPS.

How I got into cryogenics: I was fortunate to meet one of my mentors, Dr. Lukas Graber, at an electrical insulation conference in 2014. The work I presented was similar to his own PhD topic. I attended his presentation on HTS cables and was interested in learning more about HTS technology. Lukas mentioned that there was an opening for a graduate student in the research group of Dr. Sastry Pamidi, where Lukas was also a member. Six months later I found myself in Tallahassee FL, to work on HTS cables and related cryogenic dielectric materials and designs. As a result, I fell in love with the challenges of superconducting technologies and electrical insulation at cryogenic temperatures.

My mentor and my experiemce with him/her: I completed my PhD under the supervision of Dr. Sastry Pamidi and was co-advised by Dr. Lukas Graber. Sastry has encouraged my development as an independent researcher and has provided valuable guidance, not only in the experimental aspect of my work but also my professional development as I begin to establish myself as a principal investigator. Lukas has been instrumental in my understanding of electrical insulation materials and designs at cryogenic temperatures. I am extremely thankful to be able to collaborate and discuss my ideas with someone as knowledgeable as Lukas, and then act upon the creative ideas which are developed from our conversations. I have also been fortunate to learn experimental techniques at cryogenic temperature from Dr. Chul Kim. The tips, tricks, and advice Chul has given me to enable a rough sketch on a piece of paper to be transformed into an experiment at cryogenic temperatures is truly appreciated. I would like to also mention Dr. Chanyeop Park. We worked on a similar topic with a focus on fundamental understanding of dielectric properties of cryogenic gas mixtures, and both of us collaborated on the research of our PhD topics. We are continuing our collaborative work on several projects.

My present company/position: I work at Florida State University’s Center for Advanced Power Systems as research faculty. I am responsible for the day-to-day operation of the high voltage laboratory with significant cryogenic operations and measurements in liquid nitrogen and high pressure helium gas and gas mixtures. I work with and mentor several graduate/undergraduate students and collaborate with other researchers besides my own research. The high voltage lab at FSU-CAPS is one of only a few high voltage labs in the world with the capability of a broad variety of high voltage experiments at cryogenic temperatures.

Awards/honors:
—Graduate Student Research and Creativity Award, Florida State University (2017).
— The Victor Keilin Memorial Prize (Large Scale) Best Paper for “Innovations in Magnet Science and Technology” sponsored by Friends of Victor Keilin, IEEE Applied Superconductivity Conference (2016).
— 2nd Place in the Best Student Paper in Large Scale, IEEE Applied Superconductivity Conference (2016).

My contributions to the cryogenic field: My research has focused on the development of electrical insulation materials and designs for helium-gas-cooled HTS devices that operate at cryogenic temperatures. The low dielectric strength of helium gas limits the operating voltage for the HTS devices and the common electrical insulation techniques which are used for LN2-cooled HTS devices are not suitable. My research involves experimental characterization of helium gas mixtures which have higher dielectric strength than pure helium. We discovered that the addition of a small mol % of hydrogen and/or nitrogen to helium significantly increases the dielectric strength. We developed a new HTS cable design which utilizes the helium gas mixtures as both the coolant and dielectric medium of the HTS cable. We have demonstrated the potential of this design referred to as a Superconducting Gas-Insulated Transmission Line (S-GIL) which allows operation at significantly higher voltages than what is currently possible. I am currently working on advancing this technology further. I am also working on understanding the operational challenges and devising potential solutions to gas-cooled HTS cables onboard electric ships and aircrafts. The goal of my research is improve the resiliency and robustness of HTS power cables.

What are the most important developments in cryogenics? Two obstacles need to be overcome. First, the availability of reliable and low maintenance versions of large-scale cryogenic equipment. This would make the implementation of long HTS cables feasible and lead to consumer acceptance of HTS technology. The S-GIL design that we developed will have reduced thermal load and more efficient cryogenic heat transfer characteristics than the currently used HTS cable designs. The reduced thermal load should reduce the complexity of the cryogenic systems.

Second, the development of electrical insulation systems suitable for cryogenic temperatures is critical for the success of HTS power technologies. There are currently only a few electrical insulation materials and designs which are compatible with cryogenic temperature. I am contributing to the CIGRE working group D1.64 studying the fundamentals and applications of electrical insulation techniques for superconducting power apparatus and other applications at cryogenic temperatures. Development of reliable electrical insulation materials and designs will give greater consumer confidence on the reliability and resiliency of HTS power devices which should hopefully make them a more desirable option over conventional technology.

What advances do you hope to see in the future? Within my lifetime I would like to see HTS technology incorporated as an efficient and high power dense solution for the electrical power grid. Our society is dependent on electricity, and this trend is set to dramatically increase with the electrification of transportation. We will need to provide large quantities of power to urban areas which have limited easements/room for new infrastructure. HTS power device technology will be an option.
An established HTS technology market will advance demand for cryo technology in large systems.

Where can readers find out more about your projects? Google scholar https://scholar.google.com/citations?user=IV98K1MAAAAJ&hl=en or on research gate https://www.researchgate.net/profile/Peter_Cheetham2

Nikolay Bykovskiy, 28
My educational and professional background: I have a BS and MS in physics and engineering from Moscow Engineering and Physics Institute and a PhD in physics completed at École polytechnique fédérale de Lausanne.

How I got into cryogenics: I started to work in applied superconductivity in late 2010 when I joined the superconductivity group of Russian Scientific R&D cable institute.

My mentor and my experience with him/her: Professor Vitaly Vysotsky inspired me to learn about superconductivity and its applications. Under his guidance, I completed my BS and MS studies working on HTS materials. Later, he motivated me to continue my research as a PhD student at EPFL and even at long distance, Vitaly is willing to help and advise on any issues I ever have.

I was also lucky to be supervised by Pierluigi Bruzzone during my PhD, who always had time and patience to keep my studies well on the track. Under his thorough guidance, high current ReBCO fusion cables, a frontier achievement in the field, were realized.

Currently, I’m working at CERN as a postdoc, it’s a great experience to be on the team with Herman ten Kate and Alexey Dudarev, who not only provide me with new ideas for my work but also strongly support their realization.

My present company/position: I work at CERN as a postdoctoral fellow in the Experimental Physics department.

Awards/honors:
— EPFL Physics Thesis Distinction, 2018
— Plenary presentation at MT–25 conference, ’Young Scientist’ session, 2017
— IEEE CSC Graduate Study Fellowship in Applied Superconductivity, 2016

My contributions to the cryogenic field: For my MS and PhD studies, I was primarily focused on using twisted stacks of HTS tapes for high current applications. Based on this cabling layout, we performed extensive characterizations of its electromagnetic and electromechanical properties both numerically and experimentally. Encasing tape stacks in copper shells to obtain round geometry further scaled the concept up to meet the requirements of fusion conductors. As a result of full-scale R&D activity, the first 60kA/12T ReBCO tape-based cable prototypes were manufactured and successfully tested in 2015. The results demonstrated the feasibility of using HTS materials for fusion applications.

Currently, I’m involved in the development of magnet technology for detector magnets. As spin-offs of the main project—10 m long / 50 MJ NbTi dipole magnet for axion search—the novel proposals are, in particular, high current switches made of ReBCO tapes and self-protected coil windings based on canted cosine-theta winding design.

What are the most important developments in cryogenics? After many years of development, it is truly impressive how the HTS tape technology matured for the full-scale applications. However, in spite of the long list of its advantages, high cost of the materials still prevents them from coming into widespread use. I was involved in the development of high field ReBCO fusion conductors designed for applications in the central solenoid of tokamaks, which would lead to reduction of the size and the overall cost of the machines. This result not only fully justifies the use of HTS for fusion but also creates a large demand for the materials, which should reduce their cost by substantially increasing the production volume.

What advances do you hope to see in the future? I’m looking forward to the new developments in magnet technology. There is a large potential and interest in pushing the limits of generated magnetic fields in various applications, such as medicine and energy sectors. With many new ideas already proposed (>1GHz NMR magnets, compact all-ReBCO fusion reactors etc.), I’m sure many of them will come to fruition in less than 10 years.

Where can readers find out more about your projects? https://www.researchgate.net/profile/Nikolay_Bykovskiy or http://orcid.org/0000-0003-2009-3112

Roland Gyuráki, 29
My educational and professional background: I have completed my BEng (Hons) energy and environmental engineering degree at the Edinburgh Napier University in Scotland and I have a double-degree in MSc energy technologies from Karlsruhe Institute of Technology (KIT), Germany, and from Uppsala University, Sweden.

How I got into cryogenics: I attended a course on superconducting materials for energy applications during the first year of my MSc at KIT taught by my future PhD supervisor, Dr. Francesco Grilli. I was fascinated with the field and possible future applications of superconductors. I started working with superconductivity (mainly high temperature superconductors) during my master’s thesis, where I was researching the effect of transverse resistance in high temperature, filamentary, coated superconductors. Afterwards, I chose to continue with a PhD in the same field, although on a different topic.

My mentor and my experience with him/her: During my MSc thesis and throughout my PhD I received support from many people and for that I am grateful. Dr. Grilli helped and supported me from the beginning by suggesting focus points for my research, discussing the results and allowing me to work self-sufficiently. During my first year and the initial stages of my research, Professor Frédéric Sirois from Montréal also provided valuable help, sharing his knowledge and experience on the behavior of high temperature superconductors.

What is your present company/position? I am currently getting my PhD at the Institute for Technical Physics KIT where I expect to finish this year.

Awards/honors: I received the award for the best young researcher’s presentation at EUCAS 2017 in section “Large Scale”. I was chosen as one of six young researchers at the MT25 conference in 2017 to hold a five-minute plenary pitch talk to introduce my research and raise interest among fellow scientists.

My contributions to the cryogenic field: There are still several challenges to be overcome in the field of HTS, including the AC losses that arise in applications where AC current is required. One solution to reducing such losses in coated conductors is to use a filamentary structure. In my master’s thesis, I investigated the effect of transverse resistance between the filaments of coated conductors and its effects on current distribution.

Another actively researched topic is quench, a sudden loss of superconducting state and return to normal conducting conditions, which requires a deeper understanding. The rapid heating in such an event, often caused by inhomogeneous material properties, can have catastrophic consequences and may lead to destruction of the superconducting apparatus.

I am working on implementation and upscaling of a thermal imaging method, suitable for cryogenic temperatures, using a special, temperature-sensitive fluorescent material. The idea is to thermally image transient effects, such as quench, in HTS applications at time scales of a few milliseconds. By recording the fluctuations in the fluorescent light intensity over the surface of superconductor tapes with the help of a high-speed camera, I have successfully demonstrated the applicability of this thermal imaging method at 77 K.

I have moved from measuring single superconductor tapes and have wound a coil from superconductors with a novel “no-insulation” technique in order to record the thermal behavior of it under load. In such a coil, the turns are not insulated from one another, hence currents can redistribute under some circumstances, allowing bypassing weaker spots and hence contributing to a higher overall stability. Thermal imaging results have provided new insights into how and where this current redistribution happens and confirmed potential weak spots that have to be considered when designing and building larger devices.

What are the most important developments in cryogenics? I feel that ongoing research into high field insert magnets, NMR and MRI magnet applications is promising and is pushing the whole research field in a good direction. I am particularly interested in non-insulated superconducting coils, as they offer a remedy to an accidental burnout that is a major issue with common, insulated coils. Even though this additional stability comes at a cost in some respects, I believe that the significant research that has gone (and is still going) into this topic has already proven the concept and feasibility for certain applications.

What advances do you hope to see in the future? Decades have passed since the discovery of high temperature superconductors, however, truly wide-scale implementation of applications using these materials has still not occurred. We know that superconducting fault current limiters, transformers, DC current cables, motors, generators, high-field magnets and many other applications can be made from HTS, many of which would provide significant benefits over traditional counterparts. However, judging how long the widespread implementation and manufacturing of these will take is not easy. Not only do these devices have to be economically attractive, but significant research will be required to overcome existing challenges. My hope is to take part in reducing the technological challenges over the years to come.

Where can readers find out more about your projects? More details about my work and projects can be found on our institute’s website under www.itep.kit.edu and on the website of our group under http://www.itep.kit.edu/english/639.php.

Chanyeop Park, 33
My education and professional background: I completed my bachelor’s and master’s degree in electrical engineering at Hanyang University in Seoul, South Korea. I received my doctoral degree at Georgia Tech in Atlanta. Currently, I am working as a postdoctoral fellow at Georgia Tech.

How did I got into cryogenics? My research career in cryogenics started with my doctoral program, which was partially funded by the Office of Naval Research, G&W Electric Company and the National Electric Energy Research Testing and Applications Center. My work was to develop new cryogenic gas media with high dielectric strength for medium-voltage direct current superconducting power systems for electric transportation applications. For my doctoral thesis, I theoretically predicted, modeled, and experimentally verified the dielectric strength of gas media that led to the identification of several potential gas mixtures with enhanced dielectric strength. My further research includes cryogenic power electronics and modeling of AC losses in superconductors.

My mentor and my experience with him/her: No words could express my utter gratitude and respect for my advisors Professor Lukas Graber and Professor Sastry Pamidi, whom I consider my mentors.

Working with Lukas has always been pleasant and inspiring. Discussing research ideas with him has been extremely creative and open-ended. He gave me the freedom to explore and decide what the next steps should be and also guided me with his intuition when I was overlooking important factors. I have no doubt that the balance between freedom and inspiration Lukas provided me was the key to my successful research accomplishments.

Without Sastry’s positive spirit and encouragement, my research would not have developed into what it is now. Sastry has been one of the greatest champions of my research, who always encouraged my ideas and approaches. The positive energy radiated from Sastry, at times, made me believe that I had already solved a problem, which gave me great confidence, even before I began working on it.

Over the years, both Lukas and Sastry became more like a family to me. I have great trust in both of them, and they will always be my closest friends and research partners.

Awards/honors:
— College of Engineering Doctoral Student Professional Development Fund, Georgia Institute of Technology, 2017
— Graduate Conference Fund, Georgia Institute of Technology, 2017
— Global Top Talent Forum Best Presentation Award, Hyundai Motors, 2015
— Kwanjeong Educational Foundation Global Fellowship, 2013

My contributions to the cryogenic field: My doctoral research was mainly on electrically insulating properties of cryogenic gases, with the goal of improving the dielectric strength of gaseous cryogenic media for medium-voltage direct current superconducting power applications. My work involved the theoretical estimation of dielectric enhancements, modeling and designing plasma experiments, and conducting high voltage breakdown experiments.

My theoretical analysis and modeling based on electron kinetics and Gibbs free energy minimization enabled me to predict the maximum achievable dielectric strength of cryogenic gases over a wide range of temperature and pressure conditions. To confirm the theoretical predictions, I designed and conducted a plasma diagnostics experiment that was used to derive plasma parameters from the measured electron energy distribution functions and high voltage breakdown experiments.

With my doctoral research findings, I am currently taking part in a CIGRE working group, a global organization in the field of high voltage electricity that investigates the technical and economic aspects of the electrical grid as well as the environmental and regulatory aspects. I am working closely with the D1.64 working group, which collects knowledge and experimental data on the dielectric properties of cryogenic gas, liquid, and solid materials.

As a postdoctoral fellow, I am extending my doctoral research and broadening its scope. For extended research, I have theoretically estimated the dielectric strength of cryogenic gases in arcing conditions for the development of cryogenic switchgear applications. Also, I have developed cryogenic double pulse test experiments for the characterization power electronics switching devices in LN₂ and I am developing a high-power DC-DC converter that operates in LN₂. Moreover, I have tested and reported promising results regarding the feasibilities of film capacitors at cryogenic conditions. Furthermore, I am currently modeling and experimenting with AC losses in 2G (high temperature superconducting) HTS tapes.

What are the most important developments in cryogenics? I think high-performance cryogenic refrigerators and circulation systems are the key enabling technologies for the materialization of cryogenic power systems. One of the major challenges is temperature gradients formed along long cryogenic power cables, which could be addressed with the use of gaseous cryogens. I believe my doctoral research achievements contributed to enabling the use of cryogenic gas media in medium voltage power applications because my research findings showed a way to enhance the dielectric strength of cryogenic gas media by a factor of 4.5, which is now comparable to that of LN₂.

What advances do you hope to see in the future? I hope to see more applied cryogenics technology in the field of power and energy. Amid the growing demand for clean electrical energy, aging power infrastructures, and the trend towards utilizing DC systems, I believe cryogenics and superconducting technologies are promising candidates for advancing our power and energy systems.

Cryogenic power systems and devices that utilize superconductors are being considered for electric aircraft and ships because high power density is a key requirement in these applications. I expect the naval and aviation industries would be at the forefront of cryogenic power technologies, which may be followed by the terrestrial power industry in the long run.

Where can readers find out more about your projects? Most of my research has been published on our lab webpage http://graber.ece.gatech.edu, Google Scholar https://scholar.google.com/citations?user=NoJ-UA8AAAAJ&hl=en, and Research Gate https://www.researchgate.net/profile/Chanyeop_Park

Editor’s note: Part 3 will appear in an upcoming issue. ■