244 research outputs found
Interaction between Resistive Interchange Mode and Helically Trapped Energetic Ions and its Effects on the Energetic Ions and Bulk Plasmas in LHD
Simultaneous excitation of the snake-like oscillations and the m/n = 1/1 resistive interchange modes around the iota = 1 rational surface just after hydrogen pellet injections in LHD plasmas
Two types of oscillation phenomena are found just after hydrogen ice pellet injections in the Large Helical Device (LHD). Oscillation phenomena appear when the deposition profile of a hydrogen ice pellet is localized around the rotational transform ι = 1 rational surface. At first, damping oscillations (type-I) appear only in the soft X-ray (SX) emission. They are followed by the second type of oscillations (type-II) where the magnetic fluctuations and density fluctuations synchronized to the SX fluctuations are observed. Both oscillations have poloidal/toroidal mode number, m/n = 1/1. Since the type-II oscillations appear when the local pressure is large and/or the local magnetic Reynold\u27s number is small, it is reasonable that type-II oscillations are caused by the resistive interchange modes. Because both types of oscillations appear simultaneously at slightly different locations and with slightly different frequencies, it is certain that type-I oscillations are different from type-II oscillations, which we believe is the MHD instability. It is possible that type-I oscillations are caused by the asymmetric concentration of the impurities. The type-I oscillations are similar to the impurity snake phenomena observed in tokamaks though type-I oscillations survive only several tens of milliseconds in LHD
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
Excitation of helically-trapped-energetic-ion driven resistive interchange modes with intense deuterium beam injection and enhanced effect on beam ions/bulk plasmas of LHD
Energetic ion driven resistive InterChange modes (EICs) accompanying repeated bursts of the magnetic fluctuations were found in hydrogen campaign of large helical device. The pressure gradient of helically trapped energetic particles, which are mainly produced by perpendicularly injected beams, drives this mode. Recently, perpendicular neutral beam injection (PERP-NBI) systems are upgraded for deuterium plasma campaign. The beam energies of the two PERP-NBIs are increased from 40/40 keV to 60/80 keV, respectively. And the injection powers increase from 6/6 MW to 9/9 MW, as well. As results of these upgrades of NBIs, the β value of helically trapped energetic ions, , has increased up to  ∼0.35% and induced EICs with larger bursts and smaller repetition frequencies. It is found that the threshold of to excite EICs increases with deuterium PERP-NBIs. The amplitude of each burst and effect on energetic beam ions become larger when is larger. In addition, a large electrostatic potential about  −25 kV is observed when EICs are excited, which is about two times larger than the potential observed in hydrogen campaign. The transient increases of the electron density and temperature in edge regions are clearly observed when the electrostatic potential is formed
Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays
By analyzing about 33 data sample collected at and around 3.773
GeV with the BES-II detector at the BEPC collider, we directly measure the
branching fractions for the neutral and charged inclusive semimuonic decays
to be and , and determine the ratio of the two branching
fractions to be
- …