Ion acceleration and direct ion heating in three-component magnetic reconnection

Formation and sustainment of field reversed configuration (FRC) plasmas by spheromak merging and neutral beam injection

“…These TS-3 and MRX experiments demonstrated that the plasma merging formation scheme could successfully produce both spheromaks and FRCs. These experiments also revealed a violent plasma acceleration and strong ion heating during the spheromak merging process [17]. These effects were observed in both merging configurations, but they were particularly strong in the counter-helicity case.…”

“…Since spheromak plasmas are inductively formed in much slower time scale than the Alfven time, a large amount of magnetic flux can be generated resulting in a large FRC target plasma before injecting high energy ion beams. In the counter-helicity merging, a violent plasma acceleration was observed through a slingshot effect in the toroidal direction [17] as the field lines contracted after the merging of two toroidal plasmas of the opposite helicities [ Fig.2]. This acceleration mechanism and direction is significantly different from that conjectured in the typical 2-D models.…”

“…Spheromak merging was first studied on the TS-3 device at the University of Tokyo in the late 1980's and then further developed on the MRX device in 1990's [15][16][17][18][19][20][21][22]. These TS-3 and MRX experiments demonstrated that the plasma merging formation scheme could successfully produce both spheromaks and FRCs.…”

“…When the difference was larger than the threshold value, the FIGURE 2. Time evolution of the flux contours, toroidal field (red for negative values and blue for positive values), and ion temperature during the formation of an FRC plasma by merging counter-helicity spheromaks [17].…”

“…This configuration utilizes a stabilizing shell and neutral beam injection with a practically broad velocity distribution [10]. Slow formation of an FRC plasma by the merging of spheromak plasmas has been successfully demonstrated in a number of experiments as described above [15][16][17][18][19][20][21]. The experimental observation of the co-interchange instability in MRX [24] yields further motivation for the NBI system included in the SPIRIT concept.…”