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Plasma Science, IEEE Transactions on

Issue 5 • Date Oct 1995

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Displaying Results 1 - 9 of 9
  • Ion acoustic solitons in a relativistic warm plasma with density gradient

    Page(s): 813 - 815
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    Modified Korteweg-deVries equation (mK-dV), which governs the behavior of ion acoustic solitons in a relativistic warm plasma with density gradient, is derived. The electron inertia is also taken into account which is important when the streaming ions are present in the plasma. A solution of the mK-dV equation is obtained for the constant density gradient. When the ion acoustic soliton propagates into the lower plasma density region, its amplitude and energy increase, but the width decreases; the same is the case for the stronger density gradients View full abstract»

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  • Effect of charge exchange collisions on the static properties of a fully collisional ion sheath

    Page(s): 816 - 821
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    The effect of charge exchange collisions on the properties of a fully collisional, static ion sheath is considered. The existing collisional law, which excludes the effect of electrons, is derived from the fluid equations. The effect of electrons are later considered and an approximate power law solution for the potential is obtained. The effect of collisionality on the sheath properties is discussed. The approximate power law solution, derived with the help of fluid equations, is applied to find the ion energy distribution at the electrode View full abstract»

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  • The dispersion and matching characteristics of the helical resonator plasma source

    Page(s): 833 - 843
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    The dispersion characteristics and the fields of a helical resonator are obtained. The coil is approximated by a helical current layer with infinite conductivity along the current direction (a “sheath helix”). The plasma column is modeled as a cylindrical dielectric in which the dielectric losses can be neglected in determining the propagation properties of the resonator. Assuming the plasma losses are known, the model can be used to study the matching of the helical resonator to an external power source which is connected to the helix by a tap. The resonator is modeled as a parallel connection of two transmission line segments on each side of the tap position. We determine the efficiency of power transfer to the resonator as a function of the tap position driving frequency, and plasma loading. We find that whereas for a small plasma loading it is possible to achieve perfect matching, there exists a critical value of plasma loading beyond which a perfect match is no longer possible View full abstract»

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  • Multislit streak camera investigation of plasma focus in the steady-state rundown phase

    Page(s): 870 - 873
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    The technique of multislit streak photography was applied to investigate the plasma focus in the steady-state rundown phase. This enabled the axial and radial positions, and the rundown velocity of the current-carrying plasma sheath to be measured simultaneously. From these measurements, the radial profile of the plasma sheath in the plasma focus tube could be reconstructed and the plasma current was calculated. These calculated currents represented about 70% of the total circuit current flowing out of the capacitor bank, and these agreed with earlier results which were obtained via computer simulations of the measured voltage and current waveforms View full abstract»

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  • High enthalpy extraction numerical experiment in a plasma vane MHD generator

    Page(s): 844 - 851
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    A numerical experiment in a plasma vane (current carrying plasma nonuniformity) MHD generator is presented. The numerical calculations are based on a time-dependent two-dimensional model. The gas constituting the plasma is assumed to be ideal. Viscosity and heat losses are neglected. In order to optimize the generator performance, a parametric analysis is carried out. The results of the calculations indicate that enthalpy extractions larger than 30% can be obtained View full abstract»

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  • On the collisional transient sheath

    Page(s): 865 - 869
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    A theory of the transient sheath spanning the entire range of ion collisionality and treating finite rise-time voltage pulses is developed. This theory predicts the maximum ion impact energy, and the temporal dependence of the sheath width, the ion impact energy, and the ion flux. It is found that the ion impact energy is greatly reduced by even small amounts of collisionality, whereas the sheath width and ion flux at the target (i.e., ion current density) are relatively insensitive to collisionality. In the collisional sheath, the maximum ion impact energy is found to decrease with increasing rise time and collisionality. Good agreement is found between the theory and fluid simulations. In particular, the collisional dependence of the ion impact energy is well described by the theory View full abstract»

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  • Phase-locking of a second-harmonic gyrotron oscillator using a quasi-optical circulator to separate injection and output signals

    Page(s): 822 - 832
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    Phase-locking in a 34.5-GHz special complex cavity gyrotron oscillator operating at the second harmonic of the electron cyclotron frequency was studied. Injection of the locking power was made via a quasi-optical circulator connected to the gyrotron output. Locking bandwidth was measured by comparing the phase of the injection signal and output signal using a balanced mixer. Locking was observed with input power level as low as 40 dB below the gyrotron output power. The locking bandwidth is, however, narrower than in gyrotrons operating at the fundamental cyclotron frequency which may be attributed to the longer resonant cavity in the second harmonic gyrotron and the corresponding larger value of external quality factor. The measurements are roughly in agreement with predictions of Adler's phase-locking equation which is given for our system in terms of powers propagating in the output waveguide toward and away from the gyrotron cavity View full abstract»

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  • Mechanism of unstable behavior of parallel fuses as an opening switch

    Page(s): 860 - 864
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    Fuses, when used as an opening switch, are often connected in parallel to handle large energies. Here, an experiment using two fuses is carried out to understand the behavior of parallel fuses clearly. The waveforms of current flowing through each fuse are different. Unstable behaviors, in which the difference of the currents flowing into the two fuses increases, are observed, and the condition and probability of appearance of the unstable behavior are discussed. The cause of the unstable behavior is that the rate of change of fuse-resistivity with input energy is different depending on the state of the wire. Any differences in initial dimensions of the parallel fuses or any kind of disturbance during the fuse action could immediately trigger off the unstable behavior View full abstract»

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  • Comparative measurements on thermal plasma jet characteristics in atmospheric and low pressure plasma sprayings

    Page(s): 852 - 859
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    The ion and electron temperatures and plasma flow velocities are measured and compared between atmospheric and low pressure plasma spraying systems. The measurements of ion temperature for two systems are carried out by an optical emission spectroscopy which uses the relative emissivities of isolated Ar I emission lines. The electron density and temperature are measured by a Langmuir probe rotating across the plasma jets. The ion saturation currents collected by a Mach probe at two orientations, perpendicular and parallel to the plasma jet, determine the flow velocity. The spatial distributions of electron density, plasma flow velocity, and the associated shock activity in thermal plasma jets are discussed in conjunction with their direct dependency upon the ambient pressures as well as the torch powers. Measurements on temperatures and velocity profiles of thermal plasma jets reveal the general features of the LPPS jet characteristics, i.e., higher velocity flow with lower temperature, longer heating zone of expanded flame, and more extended accelerating zone compared with those of the APS jets. The shock activity clearly exists in the form of standing shock waves in the plasma jet of LPPS in view of flow compression and abrupt velocity drop which are appeared in the results of measurements on the variations of electron density and flow velocity along the plasma jet. In the center of the plasma jet of APS, the electron density is high enough to reach the LTE criterion, and the difference between ion and electron temperatures becomes insignificant as the torch input power increases View full abstract»

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IEEE Transactions on Plasma Sciences focuses on plasma science and engineering, including: magnetofluid dynamics and thermionics; plasma dynamics; gaseous electronics and arc technology.

 

 

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