S. C. Kuo

Monte Carlo simulation of electron behavior in an electron cyclotron resonance discharge

Electron behavior in an electron cyclotron resonance microwave discharge maintained by the TM01 mode fields of a cylindrical waveguide has been investigated via a Monte Carlo simulation. Since this discharge has high degree of ionization (≥1%), a self‐consistent simulation of the plasma dynamics is achieved through the use of the ponderomotive and grad B (−μ∇∥B) forces. Accumulation of negative charges on the boundary surface sets up a sheath whose influence is also taken into account. The time averaged, spatially dependent electron energy distribution (EED) is computed self‐consistently by integrating electron trajectories subjected to the microwave fields, the divergent background magnetic field, the space charge field, and the sheath field, and taking into account electron–electron collisions and collisions with the neutral hydrogen atoms. The EED is characterized by two electron temperatures with the population of the tail increasing for decreasing pressure. At low pressures (∼0.5 mTorr), the sheath p...

Analysis of the harmonic gyrotron traveling wave amplifier

A single nonlinear differential equation is derived for describing the spatial evolution of the wave field in a gyrotron amplifier of the cylindrical guide geometry. This equation is then used to determine the efficiencies and the optimized interaction lengths for gyrotrons operated with TEN1 modes at the N-th cyclotron harmonic.

The effect of axial temperature profile on the thermal instability in high current‐carrying plasmas

Current‐carrying plasmas exhibit strong temperature gradients in the proximity of bounding electrodes. A modal analysis of the thermal instability shows that a constriction always starts near the electrodes. It is localized there, where the temperature dependence of the thermal and electrical conductivities are assigned parameter values that are characteristic of plasmas in magnetohydrodynamic channels. In the case of practically full ionization and very large pressures, that prevail in arc‐driven railguns, the constriction expands axially over the entire length of the discharge.

Functional dependence of the V-I characterstic of an arc on the thermal parameters

Numerical and analytical results of a self-consistent analysis of the voltage-current (V-I) characteristic of an electrical discharge are presented. The dependences of the critical current density for the onset of the arc and the peak voltage drop on the exponent n characterizing the dependence of conductivity on temperature are examined. They are found empirically to be proportional to (n - 3/2)-(n+1)/2(n-1) and (n - 3/2)-1/2, respectively.

A generation mechanism for the frequency up-shifted plasma lines observed in the Tromso's HF heating experiments

Summary form only given. A new spectral feature in the backscattering spectrum of EIS CAT 933 MHz radar was observed throughout most of the observing period of the heating experiments performed with O-mode heater transmitting near Tromso, Norway on August 16-18, 1986. The radar returns were enhanced at frequencies offset from the radar frequency by a frequency a few hundred KHz more than the heater frequency of 4.04 MHz [Isham et al., 1990]. Thus, a different physical mechanism is considered in the present work for explaining the Tromsos observations. It is the parametric decay of a right handed circularly polarized pump wave (0-mode) into a whistler wave (decay mode) and a frequency upshifted Langmuir wave (sideband). Since the frequency of whistler wave extends to the range of a few hundred kHz, the frequency of the exited Langmuir wave agrees with that of the experimental observation.

Monte Carlo simulation of electron behavior in an electron cyclotron resonance microwave discharge

Summary form only given. Electron behavior in an electron cyclotron resonance microwave discharge maintained by the TM/sub 01/ mode fields of a cylindrical waveguide has been investigated via a Monte Carlo simulation. Since this discharge has a high degree of ionization (> 1%), a self-consistent simulation of the plasma dynamics is performed using the ponderomotive and Grad-B (-/spl muspl utrisub /spl parB) forces. Accumulation of negative charges on the boundary surface sets up a sheath whose influence is also taken into account. The time averaged, spatially dependent electron energy distribution is computed self-consistently by integrating electron trajectories subject to microwave fields, the divergent background magnetic field, the space charge field, and the sheath field, taking into account electron-electron collisions and collisions with the neutral hydrogen atoms. At low pressures (approximately 0.5 mTorr), the sheath potential is the order of 100 V and decreases with increasing pressure. This observation suggests a pressure range for operation of reactors for diamond-like carbon film deposition.

Monte-Carlo Simulation of Electron Properties in a Magnetized Microwave Discharge

Abstract Electron properties of a longitudinally magnetized ECR microwave discharge in a cylindrical waveguide are studied via a Monte-Carlo simulation. Temporally and spatially dependent TM wave solutions are obtained from the field analysis. The wave is strongly attenuated in the propagating direction. Time averaged electron energy distributions are computed by integrating, over time, electron trajectories subjected to the electromagnetic field and collisions with hydrogen molecules. Near the electron cyclotron resonance layer, the ponderomotive force exerted on electrons enhances the downstream plasma.