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March 28, 2018
Plasma Research Extending to the Fields of Energy, Medical Treatment, Industry, and Outer Space: Presentations Delivered at the National Institutes of Natural Sciences Research Symposium

The National Institutes of Natural Sciences has held the “Natural Sciences Research Symposium” since 2005. At this conference, researchers explain leading edge research in the sciences to the general public in an easy to understand manner. On March 11, 2018, under the planning and management of the National Institute for Fusion Science (NIFS), the twenty-fifth symposium was held at Nagoya University. Talks on energy development, medicine and industry, and outer space were presented, and introduced the use of plasma research in various fields.

Plasma is called the fourth state of materials, and indicates the condition iin which materials are ionized and the atomic nucleus (ion) and the electron scatter. In general, a plasma reaches a temperature of more than several thousand degrees. In plasma research that aims to realize the generation of fusion energy, NIFS generates extremely high temperatures that exceed one hundred million degrees in the device with ultra-high vacuum. Plasmas of varying temperatures are found in our environment, such as candles (approximately 2,000 degrees), auroras (approximately 10,000 degrees), and the sun (approximately 15 million degrees). Utilizing properties that respond to the temperature and the density of the plasma, research that utilizes plasma in a broad range of fields is advancing.

First, in the medical field, utilizing low temperature plasma of below 1,000 degrees that was generated under the atmospheric pressure, plasma medical research is advancing. “Cancer” is generated by abnormal proliferation of cancer cells. It has been discovered that the cancer cells ruin themselves (apoptosis) when low temperature plasmas are radiated to the cells. Due to plasma irradiation, the regeneration of central nerve cells, the alleviation of the stanching and the inflammation, and other phenomena have been found. And possibilities for new medical advances are being demonstrated. Further, high-density plasma of several tens of thousands of degrees is contributing to research of biomaterials for artificial bones and artificial dental roots. When a laser is irradiated to biomaterials in the supersaturated solution of calcium phosphate, which composes bones and teeth, the calcium phosphate film is formed on the surface of the biomaterial. The biomaterial coated with the calcium phosphate film becomes familiar with bones, and foreign-body reaction is suppressed. Further, when fluorine is added to this supersaturated solution up to appropriate fluorine density and a laser is irradiated to the solution, fluorine and calcium phosphate combine intricately at the nano-size on the biomaterial surface. It has been found that, due to this reaction, the surface function resistant to acid and cavity is given to the biomaterial. Research on functional materials utilizing these technologies is advancing.

Next, in industrial fields, atmospheric plasma of temperatures reaching several thousand degrees is being utilized. The size of transistors utilized in electronic equipment such as personal computers is extremely minute, that is, below 100 nanometers (10,000 parts to 1 of one millimeter) for leading-edge transistors. The manufacturing process of this extremely minute transistor utilizes plasma in the processes of film formation and etching. The etching is inevitable for the production of minute transistors. In the etching process the substrate of which surface is coated with oxidized film is irradiated with plasma. Ions in plasma dig in only the unnecessary parts of oxidized film and channels are formed. This technology of plasma treatment makes possible the production of super-fine transistors.

Turning to the natural world, plasma is the most common state of matter in space. The sun is composed of plasma and outer space is filled with plasma. In the sun, due to the reconnection of magnetic fields (magnetic reconnection) which appear in dark spots, the phenomenon in which a massive plasma is released abruptly occurs. This is called a solar flare. When the released plasma reaches Earth, damage to GPS positioning systems and large-scale power outages occur. Because there is the possibility of modern society receiving fatal effects from solar flare eruptions, research on space forecasts regarding the occurrence of solar flares and their effects upon Earth is advancing.

Regarding such varied plasma research, on the day of the symposium Professor Masaki Osakabe of National Institute for Fusion Science, Specially Appointed Professor Kenji Ishikawa of Nagoya University, Executive Advisory Engineer Ivan Ganashev of Shibaura Mechatronics Corporation, Principal Investigator Ayako Oyane of National Institute of Advanced Industrial Science and Technology, and Professor Kanya Kusano of Nagoya University presented speeches. Approximately 230 persons attended the event. The National Institutes of Natural Sciences symposium is held two times each year. The next symposium, too, will introduce the newest research results. We hope that all of you will attend the next symposium.