Comparative study of electron density profiles in compact torus plasma merging experiments

• Published in: Electrical engineering in Japan 2004-07, Vol.148 (2), p.14-21
• Main Authors: Hayashiya, Hitoshi, Asaka, Takeo, Katsurai, Makoto
• Format: Article
• Language: English
• Subjects: compact torus (CT); electron density profile; laser interferometer; plasma merging; spherical tokamak (ST); TS-3
• ISSN: 0424-7760; 1520-6416
• DOI: 10.1002/eej.10312

Following two previous papers on comparative studies of the electron density distributions for a single compact torus (CT) and a spherical tokamak (ST), and for a single ST and a merged ST, a comparative study on the dynamics of the electron density profile during and after the CT and ST plasma merging process was performed. The sharpness of the peak in the electron density profile around the midplane just after the merging of CT with a low safety factor (q value) such as RFP or spheromak is found to be related to the speed of the magnetic axis during the plasma merging process. It is also found that the electron density gradient near the plasma edge in a high‐q ST is larger than that of a low‐q CT. High‐q ST is found to have a magnetic structure which is able to sustain a large thermal pressure by a strong j × B force. Despite these differences in the electron density profile between CT and ST during merging, the confinement characteristics evaluated from the number of electrons confined within the magnetic separatrix after the completion of the merging are almost similar between the merging CT and the merging ST. For all configurations, the electron density profiles after the completion of the merging are analogous to those of the corresponding single configuration produced without the merging process. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(2): 14–21, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10312