Alfven ion-cyclotron modes are generated over a wide range of anisotropy parameter P±(T±/T\\) 2 in ICRF-heated central cell plasmas of the GAMMA 10 tandem mirror. The fluctuations are observed at a small driving force in the convectively unstable region predicted theoretically in an infinite plasma. Before reching the ft limit of p± = 3.52x (T\\/T±) 2 , above which the absolute instability is predicted, relaxation of pressure anisotropy is observed for the first time by use of an array of diamagnetic loops together with a Faraday cup and secondary-electron emission detectors.PACS numbers: 52.35.Qz, 52.50.Gj, 52.55.Jd Generation of an Alfven ion-cyclotron (AIC) instability is expected in a magnetized plasma with strong pressure anisotropy. However, there have been limited experimental works, especially in laboratory plasmas. The first experimental evidence of the AIC mode was performed in the end cell of the TMX tandem mirror [1,2]. A high p± (the ratio of the perpendicular plasma pressure to the magnetic field pressure) plasma with strong pressure anisotropy is produced by intense neutral-beam injection (NBI) in the direction perpendicular to the magnetic field line at the midplane of the minimum-/? mirror field. The AIC mode was also observed in an ion-cyclotron-rangeof-frequency-(ICRF-) heated plasma in the central cell of the TAR A tandem mirror [3]. The interaction between alpha particles and the generated Alfven modes is going to be a critical subject for future fusion devices. Effects of the AIC mode on the plasma parameters were described precisely in computer simulations [4][5][6][7]. Also, rapid pitch angle scattering due to the AIC mode has been simulated in a space plasma [8]. Relaxation of the pressure anisotropy is predicted theoretically; however, a direct observation of the relaxation due to the generation of the AIC mode has not been reported in laboratory plasmas.In this Letter we report a parametric study of the AIC fluctuation for a wide range of the anisotropy parameter, in order to compare with an available theory. We report the first observations of the anisotropy relaxation associated with the AIC mode in the ICRF-heated central cell plasma of the GAMMA 10 tandem mirror.GAMMA 10 is a minimum-/? anchored tandem mirror with axisymmetric plug/thermal-barrier regions at both ends [9,10]. The central cell is 5.6 m long with a field strength of 0.4 T at midplane. The mirror ratio is 5. The diameter of the limiter which is set near the midplane of the central cell is 0.36 m. Double half-turn antennas are located near the end of the central cell for ion heating at the fundamental ion-cyclotron resonance layer near the midplane. So-called Nagoya type-Ill antennas [11] are installed on the outer side of the double half-turn antennas. They are used for producing and sustaining a plas-ma, together with hydrogen gas puffing into the central cell and short-pulse (1 ms) plasma guns at both ends [12]. In the present experiment, no other heating systems such as electron-cyclotron heating (ECH) and NBI a...
We study the physical properties of a Luttinger liquid in a superlattice that is characterized by alternating two tunneling parameters. Using the bosonization approach, we describe the corresponding Hubbard model by the equivalent Tomonaga-Luttinger model. We analyze the spin-charge separation and transport properties of the superlattice system. We suggest that cold Fermi gases trapped in a bichromatic optical lattice and coupled quantum dots offer the opportunity to measure these effects in a convenient manner. We also study the classical Ising chain with two tunneling parameters. We find that the classical two-point correlator decreases as the difference between the two tunneling parameters increases.
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