Sergey Macheret | Purdue University (original) (raw)

Papers by Sergey Macheret

Nucleation and Atmospheric Aerosols, 2005

The paper reviews some of the recent studies of applications of weakly ionized plasmas to superso... more The paper reviews some of the recent studies of applications of weakly ionized plasmas to supersonic/hypersonic flight. Plasmas can be used simply as means of delivering energy (heating) to the flow, and also for electromagnetic flow control and magnetohydrodynamic (MHD) power generation. Plasma and MHD control can be especially effective in transient off-design flight regimes. In cold air flow, nonequilibrium plasmas must be created, and the ionization power budget determines design, performance envelope, and the very practicality of plasma/MHD devices. The minimum power budget is provided by electron beams and repetitive high-voltage nanosecond pulses, and the paper describes theoretical and computational modeling of plasmas created by the beams and repetitive pulses. The models include coupled equations for non-local and unsteady electron energy distribution function (modeled in forward-back approximation), plasma kinetics, and electric field. Recent experimental studies at Princeton University have successfully demonstrated stable diffuse plasmas sustained by repetitive nanosecond pulses in supersonic air flow, and for the first time have demonstrated the existence of MHD effects in such plasmas. Cold-air hypersonic MHD devices are shown to permit optimization of scramjet inlets at Mach numbers higher than the design value, while operating in self-powered regime. Plasma energy addition upstream of the inlet throat can increase the thrust by capturing more air (Virtual Cowl), or it can reduce the flow Mach number and thus eliminate the need for an isolator duct. In the latter two cases, the power that needs to be supplied to the plasma would be generated by an MHD generator downstream of the combustor, thus forming the ``reverse energy bypass'' scheme. MHD power generation on board reentry vehicles is also discussed.

2021 IEEE 21st Annual Wireless and Microwave Technology Conference (WAMICON), 2021

This paper introduces a new technology for a high-speed, high-power mobile form-factor tuner util... more This paper introduces a new technology for a high-speed, high-power mobile form-factor tuner utilizing gas discharge tube plasma cells as switching components. To the best of our knowledge, this represents the first plasma-enabled RF matching network. Technology development is reviewed, the fabrication and measurement of a proof-of-concept switched stub impedance tuner are presented, and techniques for improvement are discussed. The proof-of-concept impedance tuner functions with a 27% bandwidth from 3 to almost 4 GHz and shows a power gain better than-2.5 dB across all switching state-frequency combinations at a 50 W input power level with spread coverage of the Smith chart. State change transient timing is measured to be on the order of 500 ns. This technology demonstration highlights the potential of miniaturized, rapidly-tunable, high-power, plasma-based RF devices. Index Terms-Gas discharge tube (GDT), high-power, impedance tuner, plasma, plasma switch.

Bulletin of the American Physical Society, 2017

excellent electrical, thermal and structural properties. Roll-to-roll radio frequency chemical va... more excellent electrical, thermal and structural properties. Roll-to-roll radio frequency chemical vapor deposition (RFCVD) uses capacitively coupled radio frequency (CCRF) plasma to grow carbon nanostructures from radical precursors generated in the plasma. The transition of the plasma from the α mode dominated by impact ionization in the plasma bulk and displacement current in the sheaths, to the γ mode dominated by secondary electron emission and conduction current in the sheaths, controls the heat and precursor fluxes onto the growth substrate. Thus, characterizing these transitions under various input conditions is imperative to the optimization of the deposition. In the current work, we model CCRF plasma using the Poisson equation, hydrodynamic model with drift-diffusion approximation for electrons, modified Maxwell-Stefan equations, and the heat conduction equation. The effect of input voltage, pressure, frequency and waveform on α-to-γ transitions are studied for argon and hydrogen discharges. The differences in properties between monatomic and diatomic gases are explored for square wave voltage input.

Bulletin of the American Physical Society, 2019

capacitors and inductors are key elements of any reconfigurable RF system. Weakly ionized plasma,... more capacitors and inductors are key elements of any reconfigurable RF system. Weakly ionized plasma, and particularly CCP, devices are attractive for this because they can handle high power and because their properties can be electronically altered. In this work, we experimentally investigated two symmetric parallel-plate CCP devices: one in air, nitrogen, or argon at a pressure on the order of 1 Torr and with 2 cm gap between the electrodes, and a commercial Gas Discharge Tube (GDT) with 0.6 mm interelectrode gap. We developed a method and a setup that enabled the discharge to be sustained by a variable (10-250 MHz) excitation frequency source, and the real and imaginary parts of the device impedance to be measured at probing frequencies in the range of 300-3000 MHz. The results demonstrate wide tunability of both the magnitude and the sign of the reactance at any probing frequency by changing the excitation frequency and/or power.

Bulletin of the American Physical Society, 2017

due to the low power budget, efficient ionization, and enhanced production of excited species. To... more due to the low power budget, efficient ionization, and enhanced production of excited species. To study the dynamics of such plasmas, time-resolved probe measurements of voltage and current as well as microwave interferometry measurements of the spatially-averaged electron density were conducted in argon at a pressure of several Torr and parallel-plate electrode spacing of several centimeters. From the measured electron density decay between the pulses, the recombination rate coefficients were inferred. This provided an insight into the recombination mechanisms. In particular, the dimer ions Ar2+ were found to be dominant, so the recombination was primarily dissociative. The relaxation time of the electron temperature was also determined and found to be much shorter than the recombination time. Since the time interval between the pulses is much longer than the pulse duration and the electron temperature relaxation time, most of the time the plasma has a relatively high electron density but low electron temperature and hence low Johnson-Nyquist noise. Such plasmas could thus be useful in radio-frequency electronics.

Bulletin of the American Physical Society, 2017

2018 IEEE International Conference on Plasma Science (ICOPS), 2018

As any electrical conductor, weakly ionized plasmas can be potentially used in RF antennas, but s... more As any electrical conductor, weakly ionized plasmas can be potentially used in RF antennas, but since plasmas can be turned on and off and their properties can be changed, plasmas could form a basis for reconfigurable antennas and arrays. Modeling of resonant dipole antennas shows that if the plasma conductivity exceeds a certain level, the antenna gain should be within a few dB of similar metallic antennas. Simulation of antenna arrays also demonstrates that cross-coupling between plasma array elements would be considerably lower than that between metallic dipoles, thus giving plasma an advantage.

Physics of Fluids, 2019

A previously proposed classical impulsive model for dissociation of diatomic molecules in direct ... more A previously proposed classical impulsive model for dissociation of diatomic molecules in direct simulation Monte Carlo (DSMC), the Macheret-Fridman for direct simulation Monte Carlo (MF-DSMC) model [Luo et al., “Classical impulsive model for dissociation of diatomic molecules in direct simulation Monte Carlo,” Phys. Rev. Fluids 3, 113401 (2018)], is extended in this work. To improve the prediction of state-specific rates at high vibrational energy, the anharmonic vibrational phase angle distribution function is first incorporated into the model. Then, to improve the prediction of thermal equilibrium dissociation rates, the general concept of calculating total collision cross sections with the MF-DSMC model is discussed and the framework of implementing a collision model based on exponential potential is constructed. The improved model is validated by comparisons with quasiclassical trajectory calculations, empirical estimations, and experimental measurements. In general, better agr...

IEEE Transactions on Microwave Theory and Techniques, 2018

In this paper, a new plasma-based high-power microwave single-pole single-throw (SPST) switch is ... more In this paper, a new plasma-based high-power microwave single-pole single-throw (SPST) switch is introduced and experimentally investigated. This switch is composed of a two-pole evanescent-mode cavity structure loaded with two gas discharge tubes over its posts. Since part of the energy required for the tubes ignition is supplied by the incoming electromagnetic waves, the switching mechanism is quasi absorptive. A prototype SPST switch at the frequency range of 2.8-3.9 GHz is fabricated and successfully examined over the power range of 2-20 W. With less than 1 dB of insertion loss, the ON/OFF isolation varies from 13 dB to 22 dB, depending on the input power. The measured switching time was on the order of 10s of ns, and the input third-order intercept point (IIP3), that characterizes linearity, was +53 dBm. Upon ignition, the microwave-sustained plasma in the switch operates in the α-discharge regime, ensuring that the switch performance is quite stable, with no degradation after long periods of operation.

The European Physical Journal D, 2017

Abstract Rate constants for the Boudouard reactions: CO + CO → CO2 + C and CO + CO → C2O + O, inv... more Abstract Rate constants for the Boudouard reactions: CO + CO → CO2 + C and CO + CO → C2O + O, involving ground and vibrationally excited states for both singlet–singlet and singlet–triplet reactant CO molecules, have been obtained by using the transition-state theory on an ab initio generated potential energy surface. The dependence of the activation energies for the different processes on the vibrational energy of reactants has been estimated through a parametrization that accounts for the utilization of vibrational energy and is calculated by the forward and backward ab initio activation energies of the relevant processes at zero vibrational energy. The results and their comparison with available experimental reaction rates demonstrate the importance of vibrational excitation not only for the singlet–singlet reactions, but also for the singlet–triplet ones, which are here investigated for the first time. Finally, the implications of the present results on the kinetics of CO/CO2 cold plasmas are discussed: for their modeling the temperature dependence of the obtained rates for singlet–singlet and singlet–triplet reactants in the ground vibrational states have been represented by both Arrhenius and deformed Arrhenius equations. Graphical abstract

Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services. Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arington. VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE 3. DATES COVERED (From-To) 03-11-2006 1 FINAL 01/01/2003-12/31/2005 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Shock Control and Power Extraction by MHD Processes in Hypersonic Air Flow 5b. GRANT NUMBER F49620-03-1-0028 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Prof. Richard B. Miles and Dr. Sergey 0. Macheret 5e. TASK NUMBER 5f. WORK UNIT NUMBER

AIP Conference Proceedings, 2005

The presentation discusses recent research on conformal antennas incorporating microcavity plasma... more The presentation discusses recent research on conformal antennas incorporating microcavity plasma elements. Tests of simple dipole antennas show excellent RF reception performance and low noise fl oor. The presentation also discusses using microplasmas in metamaterial antennas that would enable those antennas to be electronically tunable.

44th AIAA Aerospace Sciences Meeting and Exhibit, 2006

In this work we demonstrate that a small amount of microwave power below its breakdown threshold ... more In this work we demonstrate that a small amount of microwave power below its breakdown threshold can be locally absorbed into a flame combustion zone. The absorbed microwave power can significantly change the flame speed of both laminar and turbulent flames. PIV technique was employed to measure the laminar flame speed. It was found that microwave assisted flame speed enhancement was greatly dependent on Q of the microwave cavity. Due to the unsteady nature of interaction, microwave assisted flame speed measurements were difficult to make, however, preliminary observations of the flame luminosity indicated that there was energy addition occurring without microwave breakdown and the flame speed was increased.

43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005

Long autoignition delay time and low lateral flame propagation speed are among the key problems i... more Long autoignition delay time and low lateral flame propagation speed are among the key problems in developing high-speed combustors for ram/scramjet engines. Plasma-assisted combustion can help to solve these problems. Estimates indicate that uniform volumetric nonequilibrium cold plasma ignition of fuel-air mixtures in ram/scramjet combustors can require large amounts of power to be deposited into the flow. In this paper, we explore a possibility of using microwaves for increase of flame propagation speed, which would be complementary to plasma ignition, allowing the latter to be applied to a smaller volume. The results suggest that the flame propagation speed strongly depends on the Q of the microwave cavity. For high values of Q (~1000), the input microwave power requirement decreases sharply from kilowatts to hundreds of watts. A 20% increase in the premixed methane-air flame propagation speed was observed for 400 Watt of input microwave power which was operating at 2.45 GHz. It was found that the power absorbed by the flame increases with the increase in the input subcritical microwave power.Theoretical estimations suggest that a small amount of power (on the order 10 W) was absorbed in the flame. These theoretical estimates support the observed experimental data.

Nucleation and Atmospheric Aerosols, 2005

2021 IEEE 21st Annual Wireless and Microwave Technology Conference (WAMICON), 2021

Bulletin of the American Physical Society, 2017

Bulletin of the American Physical Society, 2019

Bulletin of the American Physical Society, 2017

2018 IEEE International Conference on Plasma Science (ICOPS), 2018

Physics of Fluids, 2019

IEEE Transactions on Microwave Theory and Techniques, 2018

The European Physical Journal D, 2017

AIP Conference Proceedings, 2005

44th AIAA Aerospace Sciences Meeting and Exhibit, 2006

43rd AIAA Aerospace Sciences Meeting and Exhibit, 2005