A. M. Gorbachev

Numerical modeling of a microwave plasma CVD reactor

Abstract This paper presents the results of numerical simulation of a microwave CVD reactor operating in CW and pulsed regimes. Dependencies of discharge parameters on the hydrogen pressure and microwave power have been studied. The possibility to use the pulse–periodic regime of discharge for deposition of diamond films has been analyzed. It is shown that a pulsed discharge may be used to improve the quality and increase the growth rate of the films.

Studies of pulsed and continuous microwave discharges used to deposit diamond films

Results are presented from optical measurements of the atomic hydrogen density and the gas temperature in a reactor for depositing diamond films from the plasmas of pulsed and continuous microwave discharges at a fixed mean microwave power. The results obtained make it possible to explain the fact that the growth rate of diamond films in the plasma of a pulsed microwave discharge is larger than that in a continuous microwave discharge.

Modeling of plasma chemical processes in the artificial ionized layer in the upper atmosphere by the nanosecond corona discharge

Abstract The plasma chemical processes in the corona discharge formed in air by a series of high voltage pulses of nanosecond duration are investigated experimentally. The experimental conditions (reduced electric field, duration and repetition frequency of the pulses, gas pressure in the chamber) modeled the regime of creation of the artificial ionized layer (AIL) in the upper atmosphere by a nanosecond microwave discharge. It was found that in a nanosecond microwave discharge predominantly generation of ozone occurs, and that the production of nitrogen dioxide is not large. The energy expenditures for the generation of one O 3 molecule were about 15 eV. On the basis of the experimental results the prognosis of the efficiency of ozone generation in AIL was made.

Studies of pulse operation regime of microwave plasma CVD reactor

Abstract This paper presents the results of experimental investigation of the pulse regime of MPACVD reactor operation. The mole fraction of atomic hydrogen that plays an important role in the process of the film growth and the gas temperature were measured in this reactor. It was found that the use of the Ar (7504 A) line for actinometry measurements could yield erroneous results. It was shown that it is possible to measure the density of atomic hydrogen in the MPACVD reactor by observing the ratio of intensities of the H γ (4340 A)–Ar (8115 A) lines. The results obtained were compared with the numerical model.

High Power Accelerator R&D at the NRL 11.424‐GHz Magnicon Facility

An 11.424‐GHz magnicon amplifier has been jointly developed by the Naval Research Laboratory and Omega‐P, Inc. as an alternative technology to klystrons for powering a future X‐band linear collider. This paper will discuss its background, operating principles, and results to date, as well its present status as part of a facility for collaborative research on accelerator‐related technologies that require high‐power 11.424‐GHz radiation. Two collaborative research programs are currently under way using the magnicon output. The first, a collaboration with Omega‐P, Inc. and the Institute of Applied Physics, is investigating active microwave pulse compressors using plasma switch tubes. The second, a collaboration with Argonne National Laboratory and SLAC, is investigating dielectric‐loaded accelerating (DLA) structures, with the ultimate goal of developing a compact DLA accelerator.

A plasma switch based on TE02 → TE01 round waveguide mode conversion for high-power X-band microwave compressors

A new type of a plasma switch is proposed, which provides Q-switching of the energy storage cavity of a high-power microwave compressor and ensures high electric strength in all stages of compressor operation. In a compressor with this switch, the energy is accumulated on the TE02 mode and extracted on the TE01 round-waveguide mode. The principle of operation of the proposed switch is based on a sharp increase in the TE02 → TE01 mode conversion coefficient during plasma generation in an electrically controlled gas-filled discharge tube arranged in the switch. The high electric strength of the switch is ensured by placing the discharge tube surface at the node of a standing wave field formed in the switch.

Nanosecond microwave discharge as an ozone source in the upper atmosphere

Abstract The processes of ozone generation in a nanosecond microwave discharge formed in air by a series of pulses are investigated. The experimental conditions (gas pressures and temperature) corresponded to the height of the ozone layer. It was shown that at these heights ozone can be efficiently generated by microwave nanosecond pulses with insignificant production of nitrogen oxides.

Active microwave pulse compressor utilizing an axisymmetric mode of a circular waveguide

A novel active microwave pulse compressor in the form of an axisymmetric cavity is implemented and investigated. The cavity is formed by: a) a Bragg reflector, b) a cylindrical section, and c) an output resonance reflector in the form of an electrically controlled gas-filled spark gap. The compressor is excited by the TE01 mode of a circular waveguide at a frequency of 9.4 GHz. Working at atmospheric pressure, the compressor produces output pulses with a power of 1.8 MW and duration 25 ns at a compression coefficient of around 20.

Bragg superlattices formed in growing chemically vapor deposited diamond

A Bragg superlattice is created in the process of the diamond growth from a gaseous phase via the nanoscale boron modulation doping method. To maximize the Bragg superlattice reflection coefficient at the violet edge of the visible range, the thicknesses of either of two layers in its period were made close to the quarter-wavelength of radiation in this spectral domain. The vacuum wavelength dependence of the transition coefficient of electromagnetic radiation in the optical and near infrared range through this superlattice is measured. The most pronounced Bragg features are lying at the violet edge of the optical range, where the contrast of the diamond dielectric permittivity due to modulation doping is much smaller than in the red and infrared domain. Its accordance with simulation results based on secondary ion mass spectroscopy data on the thicknesses and boron atom concentrations for doped layers is demonstrated.

Hydrocarbon Plasma Chemistry in a Continuous Microwave Discharge

A study is made of the relation between the kinetic processes involving carbon-containing species and the intensity ratios of different emission lines in synthesizing diamond films in a microwave discharge plasma. The intensity ratios of the emission lines are measured as functions of the pressure, composition, and flow rate of the gas mixture. The kinetic processes involving carbon-containing components are simulated under conditions close to the experimental ones. It is shown that the intensity ratios of different pairs of lines can be used to control diamond film deposition.