In the present paper, a coaxial transmission line resonator is constructed, which is always capable of generating cold microwave plasma jet plumes in ambient air in spite of using argon, nitrogen, or even air, respectively. Although the different kind of working gas induce the different discharge performance, their ionization processes all indicate that the ionization enhancement has taken place twice in each pulsed periods, and the electron densities measured by the method of microwave Rayleigh scattering are higher than the amplitude order of 10^18m^-3. The tail region of plasma jets all contain a large number of active particles, like NO, O, emitted photons, etc., but without ozone. The formation mechanism and the distinctive characteristics are attributed to the resonance excitation of the locally enhanced electric fields, the ionization wave propulsion, and the temporal and spatial distribution of different particles in the pulsed microwave plasma jets. The parameters of plasma jet could be modulated by adjusting microwave power, modulation pulse parameters (modulation frequency and duty ratio), gas type and its flow rate, according to the requirements of application scenarios.

The microwave plasma jet has the advantage of high plasma density and abundant active particles but fails to produce large-scale microwave plasmas in ambient air which hinders the application of microwave plasma ignition and combustion. We have applied a surface wave resonator (including a Zn-coated iron wire trigger) to produce a large-scale Ar/Zn pulsed microwave plasma jet. The discharge experiment shows that the plasma jet generally presents three discharge modes, namely, filamentous argon discharge (P < 120 W), bright argon plasma filaments covered by Ar/Zn thin plasma layers (120 W ≤ P ≤ 150 W), and bright thick Ar/Zn plasma columns (P ≥ 155 W). The optical emission spectrum indicates that the electron temperature is ∼4000–5000 K, the electron density is on the order of 1015 cm−3, and the plasma has the characteristic of local thermodynamic equilibrium. According to the transient discharge photos and the simulated electric fields, the mechanism of the three discharge modes and their transformations could be attributed to the combined interactions (the mutual resonance enhancement between the surface wave and the plasma jet, the propagation of the ionization wave, and the different particle states in the Ar/Zn pulsed microwave plasma). The results have suggested that the large-scale Ar/Zn pulsed microwave plasma jet can be generated by adding Zn vapor into the Ar microwave plasma jet and the proposed Ar/Zn pulsed microwave plasma jet is suitable for the application of plasma ignition and combustion.

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The increasing number and complexity of vacuum control systems at the Stanford Synchrotron Radiation Laboratory has resulted in the need to computerize its operations in order to lower costs and increase efficiency of operation. Status signals are transmitted through digital and analog serial data links which use microprocessors to monitor vacuum status continuously.Each microprocessor has a unique address and up to 256 can be connected to the host computer over a single RS232 data line. A FORTRAN program on the host computer will request status messages and send control messages via only one RS232 line per beam line, signal the operator when a fault condition occurs, take automatic corrective actions, warn of impending valve failure, and keep a running log of all changes in vacuum status for later recall. Wiring costs are thus greatly reduced and more status conditions can be monitored without adding excessively to the complexity of the system. Operators can then obtain status reports at various locations in the lab quickly without having to read a large number of meter and LED's.

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