Compact toroid injection experiment in JFT-2M

Abstract

Compact toroid (CT) injection experiments with H mode plasmas were carried out for the first time in the JFT-2M tokamak. The soft X ray emission profile shows deep CT penetration into the core region of H mode plasmas heated by 1.2 MW NBI as well as in OH plasmas, with a toroidal magnetic field of 0.8 T. The line averaged electron density rapidly increased by ∆ne ≈ 0.2 × 10 19 m −3 at a rate of 4 × 10 21 m −3 • s −1 in H mode and the fuelling efficiency was roughly 20%. An asymmetric radial profile in the soft X ray emission was produced for ∼50 µs by deep penetration of the CT.

Deceleration mechanism of spheromak-like compact toroid penetrating into magnetized plasmas

“…The conventional simple theoretical model, which we call the conducting sphere ͑CS͒ model, has been widely employed, so far, to estimate the penetration depth of the injected CT. 2,6,8 The model indicates that the CT, for which an incompressible, perfectly conducting, sphere is substituted, penetrates by slipping through the target magnetic field, that is, the CT can penetrate until its initial kinetic energy is exceeded by the magnetic energy required to exclude the magnetic field from its volume:…”

“…In recent years, compact toroid ͑CT͒ plasmoid injection has been considered as one of the advanced fueling methods for a fusion reactor, [1][2][3][4][5][6][7][8][9][10][11][12][13][14] since the injection velocity of fuel by this method is much faster than that by any of the other methods. Since 1997, in the Japan Atomic Energy Research Institute ͑JAERI͒, the CT injection experiment into JAERI Fusion Torus-2M ͑JFT-2M͒ has been carried out in cooperation with the Himeji Institute of Technology.…”

“…Since 1997, in the Japan Atomic Energy Research Institute ͑JAERI͒, the CT injection experiment into JAERI Fusion Torus-2M ͑JFT-2M͒ has been carried out in cooperation with the Himeji Institute of Technology. 7,8 Also in the National Institute for Fusion Science, a CT injection experiment into Large Helical Device ͑LHD͒ is planned. 14 Although these studies have shown the possibility of fueling by this method, several unsolved problems have remained.…”

Effect of magnetic reconnection on CT penetration into magnetized plasmas

“…So far, the CS model has been widely employed to estimate the penetration depth of the injected CT (Raman et al, 1994;Gouge et al 1997;Ogawa et al, 1999). This model indicates that the CT, for which an incompressible, perfectly conducting sphere is substituted, penetrates by slipping through the target magnetic field, that is, the CT can penetrate until its initial kinetic energy is exceeded by the magnetic energy required to exclude the magnetic field from its volume:…”

“…It has been discussed in relation to several experimental (Brown et al, 1992;Raman et al, 1994;Raman et al, 1997;Raman et al, 1999;Gouge et al, 1997;Slough et al, 1996;Yee and Bellan, 1998;Fukumoto et al, 1996;Ogawa et al, 1999;Miyazawa et al, 1998) and theoretical (Parks et al, 1988;Perkins et al, 1988;Newcomb, 1991;Hwang et al, 1999) studies. Although these studies have shown the possibility of fuelling by this method, several unsolved problems have been remaining.…”