M.S. Dincer

Measurement of ionization and attachment coefficients in SF6 and SF6+N2

Prebreakdown ionization currents have been measured in SF6, N2, and SF6+N2 mixtures by the Townsend method over the E/p range 100–450 V cm−1 Torr−1. A digital computer analysis is used for evaluation of the ionization and attachment coefficients. The variation of (α−η)/p in SF6 and N2 mixtures is found to be nonlinear with the percentage mixture ratio. Sparkover voltage measurements are carried out for SF6, N2, and SF6+N2 mixtures in the pd interval of 3.5≤pd≤25 Torr cm. Furthermore, the apparent secondary ionization coefficients have been deduced in SF6+N2 mixtures. They decrease significantly with increasing partial pressure of SF6. The reduction observed in this coefficient is attributed to the increased photon absorption coefficient.

Monte Carlo simulation of the motion of electrons in SF6 in uniform electric fields

The motion of electrons in SF6 in uniform electric fields is simulated using a Monte Carlo technique for the range of reduced electric fields 100≤E/p≤180 V cm−1 Torr−1. The swarm parameters evaluated are compared with the experimental results of drift velocity, ratio of diffusion coefficient to mobility, ionization, and attachment coefficients. The electron‐molecule collision cross sections adopted in the simulation result in a good agreement with the experimental values over the range of E/p investigated.

Limiting fields in SF/sub 6/+argon predicted from basic data

The limiting fields in SF/sub 6/+Ar binary mixtures are evaluated directly from a Monte-Carlo simulation technique. Pulsed Townsend mean energies and time-of-flight electron drift velocities are also presented at the corresponding limiting fields.

Ionization and Attachment Coefficients in SF6 + N2 Mixtures

Steady-state ionization growth currents have been measured in N2 and SF6 + N2 mixtures in the E/N range of 1.82×101-15 ¿ E/N ¿ 2.58×10-15 V cm2. Least-square analysis is used for the evaluation of apparent ionization, ionization, and attachment coefficients. Experimental E/N limits are observed for several SF6 concentrations in the mixture. The variation of (¿-¿)/N is non-linear with the percnetage mixture ratio.

Effective Ionization Coefficients and Transport Parameters in Ultradilute

The effective ionization coefficients in ultradilute SF₆ + N₂ gas mixtures are calculated from a Monte Carlo technique over the range 100 ≤ E/N ≤ 270 Td together with electron drift velocities and pulsed Townsend mean energies. SF₆ contents in the mixtures of 0.1%, 0.3%, 0.5%, 0.7%, and 1% are considered. The effective ionization coefficients decrease with the increase of the SF₆ concentration in the mixtures at a given E/N, while the variation of the drift velocities and pulsed Townsend mean energies with respect to SF₆ concentrations is relatively constant in the E/N range of this paper.

\hbox{SF}_{6} + \hbox{N}_{2}

The limiting equivalent electric fields in Ar+SF/sub 6/ binary gas mixtures due to Townsend discharges are evaluated directly from a Monte-Carlo simulation when the mixture is subjected to orthogonal electric and magnetic fields. Along with the limiting equivalent electric fields, transverse and perpendicular drift velocities, electron mean energies and collision frequencies are also determined within the scope of the Monte-Carlo simulation. The equivalent reduced electric field (EREF) concept for the corresponding limiting electric fields is also investigated for the calculated mean energy levels and collision frequencies. The EREF values are found to be in good agreement with the previously published limiting electric field data.

Mixtures

The motion of electrons in nitrogen in uniform E*B fields is simulated using the Monte Carlo technique for 240 >

Limiting equivalent electric field response in Ar+SF/sub 6/ subjected to orthogonal electric and magnetic fields

Limiting field behavior of the electron swarms in SF/sub 6/+N/sub 2/ mixtures is investigated by a Monte Carlo simulation technique. (E/N)/sub lim/ values directly obtained from the simulation are given for 5, 10, 20, 40, 60 and 80 SF/sub 6/ fractional component in the mixture together with the corresponding electron drift velocities and mean energies. Furthermore, in the E/N range of 243/spl les/E/N/spl les/606T/sub d/, effective ionization coefficients and mean energies in SF/sub 6/+N/sub 2/ mixtures are also evaluated with fractional SF/sub 6/ contents of 0, 20, 40, 60, 80 and 100%. The simulation results obtained are compared with the available data in the literature. >

Monte Carlo simulation of electron swarms in nitrogen in uniform E*B fields

Reports electron swarm parameters in SF6 in uniform E*B fields employing a Monte Carlo simulation technique. The parameters studied are transverse and perpendicular drift velocities, magnetic deflection angle, collision frequency, mean energy and effective ionization coefficients for 30<or=E/p<or=200 V cm-1 Torr-1 and 0<or=B/p<or=6*10 T Torr-1. At a given E/p, application of a magnetic field causes decreases in the transverse drift velocity, the mean energy and the effective ionization coefficient. The validity of the effective reduced electric field concept is also investigated for the evaluated collision frequency, mean energy and effective ionization coefficient.

Simulation of limiting field behavior in electron swarms in SF/sub 6/+N/sub 2/ gas mixtures

The effective ionization coefficients and transport parameters such as electron mean energy drift velocity and transverse diffusion coefficient in binary and ultradilute SF6–Ar gas mixtures have been calculated for density reduced electric field strength E/N values from 10 to 400 Td. These calculations have been performed by using the two-term spherical harmonic expansion to obtain the numerical solution of the Boltzmann transport equation based on the finite element method under steady-state Townsend condition. In order to confirm the model and code developed in this study, the Reid ramp model has been used as a benchmark test and then effective ionization coefficients and transport parameters have been evaluated for SF6 contents of 1%, 10%, 25%, 50%, 70% and 100% in the binary mixture. Finally SF6 contents in the ultradilute mixtures of 0.1%, 0.3%, 0.5% and 0.7% are taken into account with the evaluated effective ionizations and transport parameters of electron mean energy, drift velocity and transverse diffusion coefficients.