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A killer pellet is an impurity pellet that is injected into a tokamak plasma in order to terminate a discharge without causing serious damage to the tokamak machine. In JT-60U neon ice pellets have been injected into OH and NB heated plasmas and fast plasma shutdowns have been demonstrated without large vertical displacement. The heat pulse on the divertor plate has been greatly reduced by killer pellet injection (KPI), but a low-power heat flux tail with a long time duration is observed. The total energy on the divertor plate increases with longer heat flux tail, so it has been reduced by shortening the tail. Runaway electron (RE) generation has been observed just after KPI and/or in the later phase of the plasma current quench. However, RE generation has been avoided when large magnetic perturbations are excited. These experimental results clearly show that KPI is a credible fast shutdown method avoiding large vertical displacement, reducing heat flux on the divertor plate, and avoiding (or minimizing) RE generation.

Internal modes with m = 1 and m ≥ 2, which localize around a pitch minimum, have been studied for ultra-low-q plasmas with 1/2 ≤ qa < 1 in REPUTE-1, where m is the poloidal mode number and qa is the safety factor at the plasma surface. One-dimensional stability analysis has shown that, for finite beta, m ≥ 2 modes have a relatively large growth rate compared with those of the m = 1 modes. The internal structure of the magnetic fluctuations with m = 1 and m ≥ 2 is found to be consistent with the numerically calculated eigenfunctions.

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The nonlinear dynamics and structure of plasmas with tightly twisted magnetic field lines have been studied using a toroidal plasma device. Stepwise magnetohydrodynamic (MHD) relaxation occurs, resulting in a discontinuous change in the pitch of magnetic field lines. This discrete nature of the pitch stems from the instability of kink (torsional) modes. The MHD relaxation stabilizes kink modes by selecting (self-organizing) appropriate pitches. The self-organized state displays the characteristic of a ‘dissipative structure’ in that it is accompanied by enhanced energy dissipation; the global resistance of the plasma current is substantially enhanced. The magnetic energy, which is generated by the internal plasma current, first changes into fluctuation energy through the kink instability, and then it goes mainly to ion thermal energy through viscous dissipation of the fluctuating flow. The viscosity dissipates the fluctuation energy with conservation of helicity. The self-organization of the stabilized magnetic field is characterized by the preferential conservation of the helicity.

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Tanikawa 1 J once proposed a theory of universal Fermi interactions in terms of the intermediary action of bosons with baryon number. Recently, Kinoshita 2 J suggested a test experiment of the Tanikawa theory by observing the possible resonance effect which should be produced in the scattering of the high energy neutrinos. We now point out that there still remain simple effects which are not yet measured, which should as well be expected from the Tanikawa theory. These are the energy spectra of the electrons emitted in the t3-decay, Adecay and 1'-decay.

301 Some consequences inferred from the intermediate boson hypotheses of weak interactions proposed by Tanikawa and Watanabe are suggested to be compared with the recent neutrino experiments. Some of recent experiments 1 ), 2 ) have indicated the possible existence of the resonance phenomena in the neutrino-induced events predicted by T. Kinoshita 3 ) from the intermediate boson theory of weak interactions which was proposed by one of the present authors, Y. Tanikawa, and S. Watanabe. 4 )They have suggested that the lower limit of 2130nze would be placed on the mass of the intermediate boson. In this note, we want to explore some other consequences inferred from the theory, which also could be tested by neutrino experiments. ~ I. The resonant and non-resonant neutrino elastic processesIf we assume that the conservation of nucleon and lepton holds, we can easily show that the reaction v~"+n~p+/1-IS a resonance (non-resonance) process, and the reactionis a non-resonance (resonance) process, when the effective Fermi interaction intermediated by the spin 0 boson is of the type V-A (V +A). These resonance and non-resonance characters of the processes of (I) . and (2) are in-. terchanged for the interaction intermediated by the spin 1 boson, so that (1) is non-resonant (resonant) and (2) is resonant (non-resonant), when the induced Fermi interaction is of the type, V-A (V +A). by guest on March 30, 2015 http://ptp.oxfordjournals.org/ Downloaded from