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February 8, 2017

The Nineteenth Experimental Cycle Started

The National Institute for Fusion Science has initiated its nineteenth cycle of plasma experiments. A “cycle” refers to the period of several months during which experiments are continuously conducted. This experimental cycle is the nineteenth since the first experimental cycle in Heisei 10 (1998).

During this period the Large Helical Device (LHD) has marked many achievements, including extremely important discoveries in plasma physics, in addition to setting numerous world records. For example, ion temperature, which is an indicator of plasma performance, has reached 94,000,000 degrees Kelvin, the world record in helical devices.

From this experimental cycle, we will generate plasma using deuterium gas and begin the “Deuterium Experiment,” which will seek still higher performance in plasmas. To date in world-leading experimental devices, deuterium plasma is known to have higher performance than hydrogen plasma (light hydrogen). In the LHD, too, computer simulations have predicted that performance will increase in the change from hydrogen plasma to deuterium plasma. And it is expected that the ion temperature will approach a temperature of 120,000,000 degrees Kelvin, which is the final goal of the experiment. In using deuterium, which has a mass two times greater than hydrogen, it is asked why plasma performance will increase. The reason for this increase is still not understood. Solving this riddle, too, is one of the research goals of the LHD deuterium experiment.

In the deuterium experiment, neutrons and a very small amount of tritium will be generated. The neutrons will be shielded by a concrete wall of the building, and the tritium will be recovered using a removal system. There will be no effect upon the nearby environment. The nineteenth plasma experimental cycle will begin with experiments using light hydrogen as before. Upon confirming the experimental procedures and the performance of the experimental apparatus from March 7, 2017, we will begin the conditioning experiment that will use deuterium. After having confirmed all of the safety procedures in the conditioning experiment we will begin the full-fledged deuterium experiment from after the beginning of April. In the final stage of the experiment, the hydrogen experiment will be conducted for approximately one month. The experiment is scheduled to conclude on August 3, 2017.

The National Institute for Fusion Science, together with seeking still higher plasma performance, has developed the planning for the LHD deuterium experiment that will advance research to new phases. During this period, regarding the necessity and the safety of the deuterium experiment we have accomplished numerous preparations for undertaking this experiment, and based upon the understanding of local residents and the cooperation and support of local community organizations, today we are thankful for being able to open this first day of the nineteenth experimental cycle. While feeling tense, we will move forward with experiments with safety as our first priority. We seek your continuing cooperation.