Results 1 - 10 of 3725
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[en] Several different mechanisms of emittance growth in the Accelerator Test Facility (ATF) at KEK are investigated: the author calculates rise times of the fast beam-ion instability for the damping ring (DR), and discusses the emittance growth caused by coherent synchrotron radiation in the beam-transport line (BT), the effect of quadrupole wake fields in the injector linac, and, finally, a single-bunch head-tail ion effect that can occur in both the DR and the BT. A first attempt to measure the quadrupole wake on the real machine is also reported
[en] A numerical study shows that in a cylindrical tokamak the internal kink mode (m=1) develops non-linearly into a helical equilibrium state that possesses a singular current sheet. In the large-aspect-ratio limit, the neighbouring equilibria obtained agree well with the asymptotic analytic theory of Rosenbluth et al. (author)
[en] For arbitrary closed-line magnetohydrostatic equilibria the continuous spectra are studied which correspond to singularities not in the direction of the pressure gradient. Unlike the familiar Alfven- and cusp continua, these new continua may be unstable. Their stability is governed by the closed-line version of the ballooning-mode criterion, and the corresponding growth rates are the eigenvalues of an ordinary differential operator of fourth order (rather than of second order). (author)
[en] The nonthermal effects on the Buneman instability due to the ion streaming are investigated in Lorentzian dusty plasmas. The growth rates and frequency of the Buneman instability are obtained as functions of the spectral index of the Lorentzian plasma. It is shown that the nonthermal effect suppresses the growth rates as well as the real frequency term of the unstable root. Hence, the growth rates of the Buneman instability in nonthermal plasmas are found to be always smaller than those in Maxwellian plasmas. It is also found that the nonthermal effects on the growth rates decrease with increasing wave number.
[en] Excitation of zonal flow by the modulational instability in the presence of mean shear flow is considered. The presence of the mean flow without large amplitude increases the modulational instability growth rate and favors zonal flow generation, whereas sufficiently strong mean shear significantly reduces the instability growth rate.
[en] In this paper, the authors present a method for computing growth rates and frequency shifts of a beam containing multiple non-rigid bunches. With this approach, they calculate non-rigid multibunch effects which can impact phenomena which are traditionally treated as single-bunch effects, such as the transverse mode-coupling instability. This approach is important for high current storage rings such as PEP-II at SLAC (the B-Factory) which have very strong interbunch forces. Typical calculations treat multibunch and single bunch effects separately, and thus eliminate important interactions between the two. To illustrate the technique, the authors calculate growth rates and frequency shifts using PEP-II as an example
[en] The equilibrium and stability properties of the plasma in Modified Bumpy Torus, which is an asymmetric system with closed magnetic lines of force, is reported. For small beta value, the growth rate of m=1 mode instability in MBT can be smaller than that of Scyllac configuration. The results of 1/4 toroidal sector experiment are reported. (author)
[en] Numerical simulation of the MHD instabilities in Heliotron-E lead to critical <β> values well under what is observed experimentally. If this difference persists, stellarator stability properties may be significantly better than those of Tokamaks. (author)
[en] Analytical simulations of fast-electron currents induced by high-density laser-plasma interactions require estimation of various plasma and beam parameters, including temperatures, densities, and collision rates. This note describes a technique used to estimate or calculate these parameters for the case of contemporary multi-terawatt experiments using foil targets as well as for anticipated fast-ignition-scale experiments