Department+of+Nuclear+and+Quantum+Engineering
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Electron Heating in Weakly Ionized Collisional Plasmas
(from left: Professor Wonho Choe and Research Professor Sanghoo Park)
A KAIST research team successfully identified the underlying principles behind electron heating, which is one of the most important phenomena in plasmas. As the electric heating determines wide range of physical and chemical properties of plasmas, this outcome will allow relevant industries to extend and effectively customize a range of plasma characteristics for their specific needs.
Plasma, frequently called the fourth state of matter, can be mostly formed by artificially energizing gases in standard temperature (25°C) and pressure (1 atm) range. Among the many types of plasma, atmospheric-pressure plasmas have been gaining a great deal of attention due to their unique features and applicability in various scientific and industrial fields.
Because plasma characteristics strongly depends on gas pressure in the sub-atmospheric to atmospheric pressure range, characterizing the plasma at different pressures is a prerequisite for understanding the fundamental principles of plasmas and for their industrial applications.
In that sense, information on the spatio-temporal evolution in the electron density and temperature is very important because various physical and chemical reactions within a plasma arise from electrons. Hence, electron heating has been an interesting topic in the field of plasma.
Because collisions between free electrons and neutral gases are frequent under atmospheric-pressure conditions, there are physical limits to measuring the electron density and temperature in plasmas using conventional diagnostic tools, thus the principles behind free electron heating could not be experimentally revealed.
Moreover, lacking information on a key parameter of electron heating and its controlling methods is troublesome and limit improving the reactivity and applicability of such plasmas.
To address these issues, Professor Wonho Choe and his team from the Department of Nuclear and Quantum Engineering employed neutral bremsstrahlung-based electron diagnostics in order to accurately examine the electron density and temperature in target plasmas. In addition, a novel imaging diagnostics for two dimensional distribution of electron information was developed.
Using the diagnostic technique they developed, the team measured the nanosecond-resolved electron temperature in weakly ionized collisional plasmas, and they succeeded in revealing the spatiotemporal distribution and the fundamental principle involved in the electron heating process.
The team successfully revealed the fundamental principle of the electron heating process under atmospheric to sub-atmospheric pressure (0.25-1atm) conditions through conducting the experiment on the spatiotemporal evolution of electron temperature.
Their findings of the underlying research data on free electrons in weakly ionized collisional plasmas will contribute to enhancing the field of plasma science and their commercial applications.
Professor Choe said, “The results of this study provide a clear picture of electron heating in weakly ionized plasmas under conditions where collisions between free electrons and neutral particles are frequent. We hope this study will be informative and helpful in utilizing and commercializing atmospheric-pressure plasma sources in the near future.”
Articles related to this research, led by Research Professor Sanghoo Park, were published in Scientific Reports on May 14 and July 5.
Figure 1. Nanosecond-resolved visualization of the electron heating structure. Spatiotemporal evolution of 514.5-nm continuum radiation,Te, Ar I emission
Figure 2. Nanosecond-resolved visualization of electron heating. Spatiotemporal evolution of neutral bremsstrahlung at 514.5 nm
2018.09.10 View 6092 -
NEREC Summer Program Keeps Fellows Thinking, Engaged in Nuclear Nonproliferation
Nuclear technology is more than just technology. It is the fruit of the most advanced science and technology. It also requires high standards of policymaking and global cooperation for benefiting the technology.
As part of the fifth annual Nuclear Nonproliferation Education and Research Center (NEREC) Summer Fellows Program at KAIST, 24 students from 15 countries participated in six-week intensive education and training program. NEREC is the only university-based center dedicated to nuclear nonproliferation education and research established in 2014.
The program, which provides multidisciplinary lectures and seminars on nuclear technology and policy as well as international relations, was designed to nurture global nuclear technology experts well equipped in three areas: in-depth knowledge of technology, applicability gained from sound policy building, and negotiating for international cooperation. It now has grown into the most popular summer program at KAIST.
During the program from July 6 to August 18, participants were able to engage in enriching and stimulating learning experiences in tandem with policies and technology for the utilization and provision of peaceful and safe nuclear technology.
Participating fellows also had to conduct a group research project on a given topic. This year, they explored nuclear nonproliferation issues in relation to nuclear exports and brainstormed some recommendations for current policy. They presented their outcomes at the 2018 NEREC Conference on Nuclear Nonproliferation. After intensive lecture sessions and group research work, the fellows went off to key policy think-tanks, nuclear research institutes, and research power facilities in Korea, Japan, and China.
“NEREC emphasizes nuclear nonproliferation issues related to civilian nuclear power and the associated nuclear fuel cycle development from the point of technology users. I am very glad that the number of participants are increasing year by year,” said the Director of NEREC Man-Sung Yim, a professor in the Department of Nuclear and Quantum Engineering.
Participants’ majors vary from nuclear engineering to international relations to economics. The fellows divided into two groups of graduate and undergraduate courses. They expressed their deep satisfactory in the multidisciplinary lectures by scholars from KAIST, Seoul National University, and Korea National Defense University.
Many participants reported that they learned a lot, not only about policy and international relations but on the research they are conducting and what the key issues will be in dealing for producing meaningful research work.
Moad Aldbissi from the KTH Royal Institute of Technology is one of the students who shared the same view. He said, “Coming from a technical background in nuclear engineering, I managed to learn a lot about nuclear policy and international relations. The importance of integrating the technical and political fields became even clearer.”
Most students concurred that they recognized how important it was to make international collaboration in this powerful field for each country through this program.
“As an engineering student, I just approached this program like an empty glass in policy areas. While working with colleagues during the program, I came to understand how important it is to make cooperation in these fields for the better result of national development and international relations,” said Thanataon Pornphatdetaudom from the Tokyo Institute of Technology.
To Director Yim, this program is becoming well positioned to educate nuclear policy experts in a number of countries of strategic importance. He believes the continuous supply of these experts will contribute to promoting global nuclear nonproliferation and the peaceful use of nuclear energy while the use of nuclear technology continues.
2018.09.04 View 8860 -
Extreme Materials for Fusion with Metal Cocktail
The research team under Professor Ryu Ho-jin of the Department of Nuclear and Quantum Engineering has developed a new material for facing fusion plasma environments using metal powder mixing technology. This technology is expected to extend the range of materials that can be designed for use in extreme environments such as in fusion power generators.
The durability of the tokamak vessel, which holds high-temperature plasma, is very important to create fusion power reactors, which are expected to be a future energy source. Currently, high-melting-point metals, such as tungsten, are considered plasma-facing materials to protect the tokamak vessel. However, high-energy thermal shocks, plasma ions, and neutrons are fatal to the plasma-facing material during high temperature fusion plasma operation. Therefore, it is necessary to develop new high-performance materials.
The ITER project, in which seven countries including the United States, the EU, and Korea participate jointly, is constructing a nuclear fusion experimental reactor in France with the goal of achieving the first plasma in 2025 and deuterium-tritium fusion operation in 2035. In Korea, the KSTAR tokamak at the National Fusion Research Institute has succeeded in maintaining high-performance plasma for 70 seconds.
Researchers in Europe, the United States, and China, who are leading the research on fusion plasma-facing materials, are studying the improvement of physical properties by adding a small amount of metal elements to tungsten. However, Professor Ryu’s team reported that by mixing various metals’ powders, including tungsten, they have succeeded in producing a new material that has twice the hardness and strength of tungsten. The difference in the atomic sizes of the well-mixed elements in the alloy is very significant because it makes it difficult to deform the alloy.
The team will continue its research to find alloying compositions that optimize mechanical properties as well as thermal conductivity, plasma interactions, neutron irradiation embrittlement, tritium absorption, and high-temperature oxidation properties.
Professor Ryu said, "Fusion plasma-facing materials are exposed to extreme environments and no metal is capable of withstanding thermal shock, plasma, and neutron damage simultaneously. As a result of this research, attempts to develop complex metallic materials for nuclear fusion and nuclear power are expected to become more active around the world. "
Ph.D. candidate Owais Ahmed Waseem is the first author of this project. The research is supported by the Ministry of Science, ICT and Future Planning, the Korea Research Foundation's Fusion Basic Research project, and the Engineering Research Center. The results were published in 'Scientific Report' on May 16.
Figure 1. Tungsten-based high strengh alloy sample
Figure 2. Fusion plasma facing material development by powder processing of refractory elements
2017.05.26 View 8563 -
KAIST and KTH Establish a Dual Degree Program in Nuclear Engineering
Professor Man-Sung Im, head of the Nuclear and Quantum Engineering Department at KAIST and Director Waclaw Gudowski of the Physics Department at the KTH Royal Institute of Technology in Stockholm (KTH), Sweden, agreed to establish a dual master’s degree program in the field of nuclear and quantum engineering, and signed the agreement on July 4, 2016 at the Faculty Club on the KAIST campus.
Following the first joint degree program in mechanical engineering in 2014, this is the second dual degree program created between the two universities.
Under the agreement, which will be effective beginning in the 2016 fall semester, KAIST and KTH will exchange students, confer students dual degrees when they earn the required number of credits, and support financial aid for exchange students.
Dean Im said, “The two schools have enjoyed an excellent reputation in nuclear and quantum engineering, and offering students more opportunities to study abroad at the other university will produce synergistic effects for the growth of the two schools' education and research.”
Founded in 1827, KTH is regarded one of the most prestigious universities in Northern Europe.
Professor Man-Sung Im of KAIST’s Nuclear and Quantum Engineering (pictured on the left) and Director Waclaw Gudowski of KTH’s Physics Department are shaking hands after signing the agreement for the dual master’s degree program.
2016.07.05 View 8422 -
Omnidirectional Free Space Wireless Charging Developed
The simultaneous charging of multiple mobile devices at 0.5 meter away from the power source is now possible under the international electromagnetic field guidelines.
Mobile devices, such as smartphones and laptops, have become indispensable portable items in modern life, but one big challenge remains to fully enjoying these devices: keeping their batteries charged.
A group of researchers at KAIST has developed a wireless-power transfer (WPT) technology that allows mobile devices to be charged at any location and in any direction, even if the devices are away from the power source, just as Wi-Fi works for Internet connections. With this technology, so long as mobile users stay in a designated area where the charging is available, e.g., the Wi-Power zone, the device, without being tethered to a charger, will pick up power automatically, as needed.
The research team led by Professor Chun T. Rim of the Nuclear and Quantum Engineering Department at KAIST has made great strides in WPT development. Their WPT system is capable of charging multiple mobile devices concurrently and with unprecedented freedom in any direction, even while holding the devices in midair or a half meter away from the power source, which is a transmitter. The research result was published in the June 2015 on-line issue of IEEE Transactions on Power Electronics, which is entitled “Six Degrees of Freedom Mobile Inductive Power Transfer by Crossed Dipole Tx (Transmitter) and Rx (Receiver) Coils.”
Professor Rim’s team has successfully showcased the technology on July 7, 2015 at a lab on KAIST’s campus. They used high-frequency magnetic materials in a dipole coil structure to build a thin, flat transmitter (Tx) system shaped in a rectangle with a size of 1m2. Either 30 smartphones with a power capacity of one watt each or 5 laptops with 2.4 watts each can be simultaneously and wirelessly charged at a 50 cm distance from the transmitter with six degrees of freedom, regardless of the devices’ three-axes positions and directions. This means that the device can receive power all around the transmitter in three-dimensional space. The maximum power transfer efficiency for the laptops was 34%. The researchers said that to fabricate plane Tx and Rx coils with the six-degree-of-freedom characteristic was a bottleneck of WPT for mobile applications.
Dipole Coil Resonance System (DCRS)
The research team used the Dipole Coil Resonance System (DCRS) to induce magnetic fields, which was developed by the team in 2014 for inductive power transfer over an extended distance. The DCRS is composed of two (transmitting and receiving) magnetic dipole coils, placed in parallel, with each coil having a ferrite core and connected with a resonant capacitor. Comparing to a conventional loop coil, the dipole coil is very compact and has a less dimension. Therefore, a crossed dipole structure has 2-dimension rather than 3-dimension of a crossed loop coil structure. The DCRS has a great advantage to transfer power even when the resonance frequency changes in the range of 1% (Q factor is below 100). The ferrite cores are optimally designed to reduce the core volume by half, and their ability to transfer power is nearly unaffected by human bodies or surrounding metal objects, making DCRS ideal to transmit wireless power in emergency situations. In a test conducted in 2014, Professor Rim succeeded in transferring 209 watts of power wirelessly to the distance of five meters. (See KAIST’s press release on DCRS for details: http://www.eurekalert.org/pub_releases/2014-04/tkai-wpt041714.php.)
Greater Flexibility and Safer Charging
The research team rearranged the two dipole coils from a parallel position to cross them in order to generate rotating magnetic fields, which was embedded in the Tx’s flat platform. This has made it possible for mobile devices to receive power from any direction.
Although wireless-power technology has been applied to smartphones, it could not offer any substantial advantages over traditional wired charging because the devices still require close contact with the transmitter, a charging pad. To use the devices freely and safely, including in public spaces, the WPT technology should provide mobile users with six degrees of freedom at a distance. Until now, all wireless-charging technologies have had difficulties with the problem of short charging distance, mostly less than 10 cm, as well as charging conditions that the devices should be placed in a fixed position. For example, the Galaxy S6 could only be charged wirelessly in a fixed position, having one degree of freedom. The degree of freedom represents mobile devices’ freedom of movement in three-dimensional space.
In addition, the DCRS works at a low magnetic field environment. Based on the magnetic flux shielding technology developed by the research team, the level of magnetic flux is below the safety level of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guideline (27µT) for general public exposure to electromagnetic field (EMF).
Professor Rim said, “Our transmitter system is safe for humans and compatible with other electronic devices. We have solved three major issues of short charging distance, the dependence on charging directions, and plane coil structures of both Tx and Rx, which have blocked the commercialization of WPT.”
Currently, the research team and KAIST’s spin-off company, TESLAS, Inc., have been conducting pilot projects to apply DCRS in various places such as cafes and offices.
YouTube Link: https://www.youtube.com/watch?v=JU64pMyJioc
Demonstration of 30 Watts Range Omnidirectional Wireless-charging at a Laboratory on KAIST’s Campus
Figure 1: Wide-range omnidirectional wireless-charging system based on DCRS can charge multiple numbers of mobile devices simultaneously in a 1m3 range. The above is a transmitter, and the below is a Samsung Galaxy Note with a receiver embedded inside.
Figure 2: Demonstration of the omnidirectional wireless-charging system (clockwise from top of the left, robust charging despite the presence of metal obstacles, omnidirectional charging, long distance charging, and multiple devices charging)
2015.07.08 View 16002 -
KAIST-Saudi Nuclear Workforce Training
Nuclear Engineering Intensive Course Program Held in Saudi Arabia from January 5th to 23rd
KUSTAR (The Khalifa University of Science and Technology Studies)-KAIST Institute of Education began its Nuclear Engineering Intensive Course Program on 5th January with researchers from K.A.CARE (King Abdullah City for Atomic and Renewable Energy) of Riyadh, Saudi Arabia.
This program, which was lasted until 23rd January, provided education to students on the basic technologies in the field of nuclear power.
The course involves a wide range of lectures, such as basic nuclear physics, applications using radiation, nuclear reactor design and safety, as well as nuclear power engineering.
In order to utilize the nuclear power and renewable energy, K.A.CARE was established in April 2010. The institution is also involved in the construction of nuclear infrastructure, including the site investigations, the establishment of regulatory bodies and state-owned nuclear companies, along with the newly launched workforce-training program.
The Director of the KUSTAR-KAIST Education Research Institute, Professor Soong-Heung Jang said, “This program is the beginning of long-term cooperation with Saudi Arabia. Our experience can be the basis for the construction of an extensive training program that involves many areas of nuclear engineering field.”
KAIST has been working in close cooperation with various institutions around the world, which also includes the establishment of KUSTAR-KAIST Institute of Education and Research in July 2010. KAIST is also actively cooperating with UAE Khalifa University in Middle East, sharing faculty, holding joint research programs and exchanging students.
2014.02.03 View 9747 -
The key to Alzheimer disease, PET-MRI made in Korea
Professor Kyu-Sung Cho
- Simultaneous PET-MRI imaging system commercialization technology developed purely from domestic technology - - Inspiring achievement by KAIST, National NanoFab Center, Sogang University, Seoul National University Hospital –
Hopes are high for the potential of producing domestic products in the field of state-of-the-art medical imaging equipment that used to rely on imported products.
The joint research team (KAIST, Sogang University and Seoul National University) with KAIST Department of Nuclear and Quantum Engineering Professor Kyu-Sung Cho in charge, together with National Nanofab Institution (NNFC; Director Jae-Young Lee), has developed PET-MRI simultaneous imaging system with domestic technology only. The team successfully acquired brain images of 3 volunteers with the newly developed system.
PET-MRI is integrated state-of-the-art medical imaging equipment that combines the advantages of Magnetic Resonance Imaging (MRI) that shows anatomical images of the body and Position Emission Tomography (PET) that analyses cell activity and metabolism. Since the anatomical information and functional information can be seen simultaneously, the device can be used to diagnose early onset Alzheimer’s disease and is essential in biological science research, such as new medicine development.
The existing equipment used to take MRI and PET images separately due to the strong magnetic field generated by MRI and combine the images. Hence, it was time consuming and error-prone due to patient’s movement. There was a need to develop PET that functions within a magnetic field to create a simultaneous imaging system.
The newly developed integral PET-MRI has 3 technical characteristics: 1. PET detector without magnetic interference, 2. PET-MRI integration system, 3.PET-MRI imaging processing.
The PET detector is the most important factor and accounts for half the cost of the whole system. KAIST Professor Cho and NNFC Doctor Woo-Suk Seol’s team successfully developed the Silicon Photomultiplier (amplifies light coming into the radiation detector) that can be used in strong magnetic fields. The developed sensor has a global competitive edge since it optimises semiconductor processing to yield over 95% productivity and around 10% gamma radiation energy resolving power.
Sogang University Department and Electrical Engineering Professor Yong Choi developed cutting edge PET system using a new concept of electric charge signal transmission method and imaging location distinction circuit. The creativity and excellence of the research findings were recognised and hence published on the cover of Medical Physics in June.
Seoul National University Hospital Department of Nuclear Medicine Professor Jae-Sung Lee developed the Silicon Photomultiplier sensor based PET imaging reconstitution programme, MRI imaging based PET imaging revision technology and PET-MRI imaging integration software.
Furthermore, KAIST Department of Electrical Engineering Professor Hyun-Wook Park was responsible for the development of RF Shielding technology that enables simultaneous installation of PET and MRI and using this technology, he developed a head coil for the brain that can be connected to PET for installation.
Based on the technology describe above, the joint research team successfully developed PET-MRI system for brains and acquired PET-MRI integrated brain images from 3 volunteers last June.
In particular, this system has the distinct feature of a detachable PET module and MRI head coil to the existing whole body MRI, so that PET-MRI simultaneous imaging is possible with low installation cost.
Professor Cho said, “We have prepared the foundation of domestic commercial PET and the system has a competitive edge in the global market of PET-MRI system technology.” He continued, “It can reduce the cost of the increasing brain related disease diagnosis, including Alzheimer’s, dramatically.”
Funded by Ministry of Trade, Industry and Energy as an Industrial Foundation Technology Development Project (98 billion won in 7 years), the research applied for over 20 patents and 20 CSI theses.
Figure 1.Brain phantom images from developed PET-MRI system
Figure 2. Brain images from developed PET-MRI system
Figure 3. Domestic PET-MRI clinical trial
Figure 4. Head RF coil and PET detector inserted in MRI
Figure 5. Insertion type PET detector module
Figure 6. Silicon Photomultiplier sensor (Left) and flash crystal block (right)
Figure7. Silicon Photomultiplier sensor
Figure 8. PET detection principle
2013.11.28 View 12426 -
New wireless charging device developed
The On-line Electric Vehicle (OLEV) developed by KAIST has made a step towards commercialization with the development of a more economic wireless charging device.
Professor Chun-Taek Rim from the Department of Nuclear and Quantum Engineering at KAIST has developed a new I-shaped wireless charging device that differs from the pre-existing rail-type electricity feeder. This device can be modularly produced and requires relatively less construction, significantly reducing the cost of implementation.
The KAIST OLEV is a new concept electric car that has a special electricity collecting device underneath it. The car’s battery is charged by magnetic fields produced from electric lines buried 15cm underneath the road. The vehicle was first tested in 2009, making it the first wireless electric car in the world. OLEV can be charged during stoppage time between traffic lights and receives real-time power when running. OLEV is currently in operation at the KAIST Munji Campus in Daejeon and is also being exhibited at the Yeosu Expo and Seoul Grand Park.
The device itself has a charging capacity of 15kW, and the electricity is supplied through an electricity feeder with a width of 80cm with a space interval of 20cm. Despite being hailed as a technological breakthrough and revolutionary concept, KAIST OLEV has been criticized for problems in commercialization, due to the difficulties in installing wires beneath existing roads, which costs a considerable amount of money.
The new I-shaped wireless charging device reduces the width of the electricity feeder by 10cm, a mere one-eighth of the size of the previous version, and greatly increases the charging power to 25kW. Furthermore, the left and right permissible space of automobiles has increased to 24cm and the magnetic field complies with the international design guidelines, making the OLEV safe for the human body.
The reduction of the width has made the mass production of modules possible, making the installation of KAIST OLEV more economical and marketable. Professor Rim emphasized that compared with the existing rail-type electricity feeder, the new technology will need only one-tenth of the construction time and 80% of the cost, significantly improving OLEV’s constructability and workability.
The research was published in the IEEE Transactions on Power Electronics last December, and Professor Rim was invited to talk at the Conference on Electric Roads & Vehicles, which was held in February in the United States, about the new technology.
2012.07.06 View 10772