A. Fruchtman - Academia.edu (original) (raw)

Papers by A. Fruchtman

Research paper thumbnail of The time-dependent electron density and magnetic field distributions in a 70-ns plasma opening switch

12th International Conference on High-Power Particle Beams. BEAMS'98. Proceedings (Cat. No.98EX103)

ABSTRACT

Research paper thumbnail of Strong cyclotron damping of electron cyclotron waves in nearly parallel stratified plasmas

Propagation of extraordinary mode waves in nearly parallel stratified plasmas (magnetic beach geo... more Propagation of extraordinary mode waves in nearly parallel stratified plasmas (magnetic beach geometry) is investigated. Since the plasma is unable to shield out the right circular component of the electric field, these waves are very heavily damped. The resonance region is treated by a boundary layer expansion which reduces the problem to an integrodifferential system in one dimension. It is proved analytically that for moderate to high density, waves incident from the high field side are totally absorbed with no reflected wave. At very low density some transmission is possible, where the transmission coefficients are being given correctly by cold plasma theory. Numerical solution of the integrodifferential system shows that the power deposition profile can differ significantly from that predicted from a local WKB theory.

Research paper thumbnail of Low Power Hall Thrusters for Small Satellites

Research paper thumbnail of Breakdown of the Brillouin limit and classical fluxes in rotating collisional plasmas

Physics of Plasmas, 2015

The classical collisionless analysis displaying the occurrence of slow and fast rigid body rotati... more The classical collisionless analysis displaying the occurrence of slow and fast rigid body rotation modes in magnetized plasmas is extended to collisional discharges. Collisions speed up the fast mode, slow down the slow one, and break down the classical Brillouin limit. Rigid body rotation has a strong impact on transport, and a collisional radial transport regime, different from the classical Braginskii collisional flux, is identified and analyzed.

Research paper thumbnail of Observation of ion velocity distributions and electric fields in a plasma opening switch

Research paper thumbnail of Magnetic Field Evolution, Flux Penetration And energy dissipation due to the Hall field in the plasma opening switch configuration

Research paper thumbnail of Plasma transport under neutral gas depletion conditions

Journal of Physics D: Applied Physics, 2007

Research paper thumbnail of Investigation of electric fields in plasmas under pulsed currents

Interaction of the magnetic field with plasmas is an intriguing subject of modern plasma physics. ... more Interaction of the magnetic field with plasmas is an intriguing subject of modern plasma physics. Detailed and reliable measurements of the key plasma parameters, as well as the development of the diagnostic methods, are highly required for improving the ...

Research paper thumbnail of Heat Flux Measurements in the Hall Thruster Plume

A heat flux probe has been developed for the purpose of measuring the heat flux density in the pl... more A heat flux probe has been developed for the purpose of measuring the heat flux density in the plume of the Hall thruster. The measurement is based on comparing the rates of heating and cooling of the probe during its exposure to and isolation from the plasma flow. In the case of a helicon plasma source this is accomplished easily by turning on and off the plasma flow. The measured heat flux into the negatively-biased probe is in a very good agreement with the calculated heat flux carried by the impinging plasma ions, indicating that there are no energetic neutrals. This method will be employed for the plume of the Hall thruster and is expected to provide an estimate of the heat flux carried by energetic neutrals.

Research paper thumbnail of Particle and energy balance in a Helicon plasma source

Research paper thumbnail of Modification of short scale-length tearing modes by the Hall field

Physics of Fluids B: Plasma Physics, 1993

The calculation of the growth rate of tearing modes is extended to short scale lengths by includi... more The calculation of the growth rate of tearing modes is extended to short scale lengths by including the Hall field. A unified dispersion relation is found that describes usual tearing modes at one limit and the Hall tearing modes with the enhanced growth rate at the opposite limit. The dispersion relation is valid for both collisional and collisionless plasmas.

Research paper thumbnail of Additional information on Phys. Plasmas

Research paper thumbnail of Optical guiding in a sheet-beam free-electron laser

Physical Review A, 1988

The inAuence of electron density gradients on optical guiding in free-electron lasers (FEL's) is ... more The inAuence of electron density gradients on optical guiding in free-electron lasers (FEL's) is considered. %'e study a model problem of a FEL which employs a sheet electron beam in the absence of a cavity or a waveguide. %'e calculate the gain and the rate of optical guiding by solving for the eigenvalues and the actual eigenmodes of the system. Similar to what has been found by Moore for a cylindrical beam [Nucl. Instrum. Methods A239, 19 (1985)], we find that two parameters characterize the interaction: a coupling parameter and a detuning parameter. We solve the problem for two density profiles, a uniform density profile and a triangular-shaped density profile. For large and small values of the coupling parameter we obtain the results analytically. For intermediate values of the coupling parameter we obtain numerical results. %'hen the coupling parameter is small"diffraction is large. The gain and the wave profile are then similar for the two density profiles. When the coupling parameter is large, optical guiding is large. The gain for the triangular-shaped beam is then larger by 2' ' than the gain for the uniform beam. W'hen the coupling parameter is large, the wave profile for the uniform density beam converges to a certain profile confined to the beam volume. For the triangular-shaped beam the wave profile becomes more and more concentrated near the midplane of the sheet beam. For the solution of the problem we derive an energy integral that determines the domain in the complex plane where nonreal eigenvalues are allowed. We also show the existence of an accumulation point of nonreal eigenvalues in certain cases.

Research paper thumbnail of Thermomagnetic instability in a magnetized plasma

Physics of Fluids B: Plasma Physics, 1992

The thermomagnetic instability, driven by gradients of the plasma density and temperature, which ... more The thermomagnetic instability, driven by gradients of the plasma density and temperature, which are parallel to each other and orthogonal to the magnetic field, is studied. The focus of this paper is on a magnetized plasma, in which the electron cyclotron frequency is larger than the electron collision frequency. The nature of the transverse heat conductivity in the magnetized plasma causes the instability to be driven by opposite density and temperature gradients. The growth rate in the magnetized plasma is much smaller than in the unmagnetized plasma. In a very strong magnetic field heat convection is larger than heat conduction, and the instability is further stabilized by the Hall field.

Research paper thumbnail of Mass separation in a 100-ns plasma opening switch

IEEE Conference Record - Abstracts. 1999 IEEE International Conference on Plasma Science. 26th IEEE International Conference (Cat. No.99CH36297)

ABSTRACT

Research paper thumbnail of Evolution of a magnetic field and plasma pushing in the presence of a parallel magnetic field

Physics of Fluids B: Plasma Physics, 1992

Research paper thumbnail of Neutral gas depletion in low temperature plasma

Journal of Physics D: Applied Physics, 2017

Research paper thumbnail of A kinetic full wave theory of strong spatial damping of electron cyclotron waves in nearly parallel stratified plasmas

Physics of Fluids, 1987

ABSTRACT

Research paper thumbnail of Simulations Of Fast Magnetic Field Penetration Into A Plasma

Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)

Fast magnetic field penetration into plasmas has been hypothesized as a possible explanation for ... more Fast magnetic field penetration into plasmas has been hypothesized as a possible explanation for the operation of plasma opening switches. The authors have begun an in-depth numerical study of the behavior of plasma opening switches (POS),a nd relevant experimental results. Simulations using the 2-1/2 dimensional PIC codes OOPIC, MAGIC, and ISIS are compared with theory. Because of the difficulty in applying and comparing PIC simulations to actual POS experiments, the numerical work is at present concerned with validating the more modest scenarios predicted by theory, e.g., the penetration skin depth of the magnetic field. The state-of-the-art graphical user interface of OOPIC is especially convenient for observing the field penetration as a real-time movie. A review of previous experiments (NRL, Weizmann, etc.) will be examined to indicate if the phenomenon of fast magnetic field penetration into plasmas can account for some experimental observations. Experimental scenarios, e.g., the direction of the density gradients, values of the plasma collision frequency, electron orbits, etc. in a typical POS are discussed.

Research paper thumbnail of Channel length and wall recombination effects in the Hall thruster

36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2000

Research paper thumbnail of The time-dependent electron density and magnetic field distributions in a 70-ns plasma opening switch

12th International Conference on High-Power Particle Beams. BEAMS'98. Proceedings (Cat. No.98EX103)

ABSTRACT

Research paper thumbnail of Strong cyclotron damping of electron cyclotron waves in nearly parallel stratified plasmas

Propagation of extraordinary mode waves in nearly parallel stratified plasmas (magnetic beach geo... more Propagation of extraordinary mode waves in nearly parallel stratified plasmas (magnetic beach geometry) is investigated. Since the plasma is unable to shield out the right circular component of the electric field, these waves are very heavily damped. The resonance region is treated by a boundary layer expansion which reduces the problem to an integrodifferential system in one dimension. It is proved analytically that for moderate to high density, waves incident from the high field side are totally absorbed with no reflected wave. At very low density some transmission is possible, where the transmission coefficients are being given correctly by cold plasma theory. Numerical solution of the integrodifferential system shows that the power deposition profile can differ significantly from that predicted from a local WKB theory.

Research paper thumbnail of Low Power Hall Thrusters for Small Satellites

Research paper thumbnail of Breakdown of the Brillouin limit and classical fluxes in rotating collisional plasmas

Physics of Plasmas, 2015

The classical collisionless analysis displaying the occurrence of slow and fast rigid body rotati... more The classical collisionless analysis displaying the occurrence of slow and fast rigid body rotation modes in magnetized plasmas is extended to collisional discharges. Collisions speed up the fast mode, slow down the slow one, and break down the classical Brillouin limit. Rigid body rotation has a strong impact on transport, and a collisional radial transport regime, different from the classical Braginskii collisional flux, is identified and analyzed.

Research paper thumbnail of Observation of ion velocity distributions and electric fields in a plasma opening switch

Research paper thumbnail of Magnetic Field Evolution, Flux Penetration And energy dissipation due to the Hall field in the plasma opening switch configuration

Research paper thumbnail of Plasma transport under neutral gas depletion conditions

Journal of Physics D: Applied Physics, 2007

Research paper thumbnail of Investigation of electric fields in plasmas under pulsed currents

Interaction of the magnetic field with plasmas is an intriguing subject of modern plasma physics. ... more Interaction of the magnetic field with plasmas is an intriguing subject of modern plasma physics. Detailed and reliable measurements of the key plasma parameters, as well as the development of the diagnostic methods, are highly required for improving the ...

Research paper thumbnail of Heat Flux Measurements in the Hall Thruster Plume

A heat flux probe has been developed for the purpose of measuring the heat flux density in the pl... more A heat flux probe has been developed for the purpose of measuring the heat flux density in the plume of the Hall thruster. The measurement is based on comparing the rates of heating and cooling of the probe during its exposure to and isolation from the plasma flow. In the case of a helicon plasma source this is accomplished easily by turning on and off the plasma flow. The measured heat flux into the negatively-biased probe is in a very good agreement with the calculated heat flux carried by the impinging plasma ions, indicating that there are no energetic neutrals. This method will be employed for the plume of the Hall thruster and is expected to provide an estimate of the heat flux carried by energetic neutrals.

Research paper thumbnail of Particle and energy balance in a Helicon plasma source

Research paper thumbnail of Modification of short scale-length tearing modes by the Hall field

Physics of Fluids B: Plasma Physics, 1993

The calculation of the growth rate of tearing modes is extended to short scale lengths by includi... more The calculation of the growth rate of tearing modes is extended to short scale lengths by including the Hall field. A unified dispersion relation is found that describes usual tearing modes at one limit and the Hall tearing modes with the enhanced growth rate at the opposite limit. The dispersion relation is valid for both collisional and collisionless plasmas.

Research paper thumbnail of Additional information on Phys. Plasmas

Research paper thumbnail of Optical guiding in a sheet-beam free-electron laser

Physical Review A, 1988

The inAuence of electron density gradients on optical guiding in free-electron lasers (FEL's) is ... more The inAuence of electron density gradients on optical guiding in free-electron lasers (FEL's) is considered. %'e study a model problem of a FEL which employs a sheet electron beam in the absence of a cavity or a waveguide. %'e calculate the gain and the rate of optical guiding by solving for the eigenvalues and the actual eigenmodes of the system. Similar to what has been found by Moore for a cylindrical beam [Nucl. Instrum. Methods A239, 19 (1985)], we find that two parameters characterize the interaction: a coupling parameter and a detuning parameter. We solve the problem for two density profiles, a uniform density profile and a triangular-shaped density profile. For large and small values of the coupling parameter we obtain the results analytically. For intermediate values of the coupling parameter we obtain numerical results. %'hen the coupling parameter is small"diffraction is large. The gain and the wave profile are then similar for the two density profiles. When the coupling parameter is large, optical guiding is large. The gain for the triangular-shaped beam is then larger by 2' ' than the gain for the uniform beam. W'hen the coupling parameter is large, the wave profile for the uniform density beam converges to a certain profile confined to the beam volume. For the triangular-shaped beam the wave profile becomes more and more concentrated near the midplane of the sheet beam. For the solution of the problem we derive an energy integral that determines the domain in the complex plane where nonreal eigenvalues are allowed. We also show the existence of an accumulation point of nonreal eigenvalues in certain cases.

Research paper thumbnail of Thermomagnetic instability in a magnetized plasma

Physics of Fluids B: Plasma Physics, 1992

The thermomagnetic instability, driven by gradients of the plasma density and temperature, which ... more The thermomagnetic instability, driven by gradients of the plasma density and temperature, which are parallel to each other and orthogonal to the magnetic field, is studied. The focus of this paper is on a magnetized plasma, in which the electron cyclotron frequency is larger than the electron collision frequency. The nature of the transverse heat conductivity in the magnetized plasma causes the instability to be driven by opposite density and temperature gradients. The growth rate in the magnetized plasma is much smaller than in the unmagnetized plasma. In a very strong magnetic field heat convection is larger than heat conduction, and the instability is further stabilized by the Hall field.

Research paper thumbnail of Mass separation in a 100-ns plasma opening switch

IEEE Conference Record - Abstracts. 1999 IEEE International Conference on Plasma Science. 26th IEEE International Conference (Cat. No.99CH36297)

ABSTRACT

Research paper thumbnail of Evolution of a magnetic field and plasma pushing in the presence of a parallel magnetic field

Physics of Fluids B: Plasma Physics, 1992

Research paper thumbnail of Neutral gas depletion in low temperature plasma

Journal of Physics D: Applied Physics, 2017

Research paper thumbnail of A kinetic full wave theory of strong spatial damping of electron cyclotron waves in nearly parallel stratified plasmas

Physics of Fluids, 1987

ABSTRACT

Research paper thumbnail of Simulations Of Fast Magnetic Field Penetration Into A Plasma

Proceedings of 1994 IEEE 21st International Conference on Plasma Sciences (ICOPS)

Fast magnetic field penetration into plasmas has been hypothesized as a possible explanation for ... more Fast magnetic field penetration into plasmas has been hypothesized as a possible explanation for the operation of plasma opening switches. The authors have begun an in-depth numerical study of the behavior of plasma opening switches (POS),a nd relevant experimental results. Simulations using the 2-1/2 dimensional PIC codes OOPIC, MAGIC, and ISIS are compared with theory. Because of the difficulty in applying and comparing PIC simulations to actual POS experiments, the numerical work is at present concerned with validating the more modest scenarios predicted by theory, e.g., the penetration skin depth of the magnetic field. The state-of-the-art graphical user interface of OOPIC is especially convenient for observing the field penetration as a real-time movie. A review of previous experiments (NRL, Weizmann, etc.) will be examined to indicate if the phenomenon of fast magnetic field penetration into plasmas can account for some experimental observations. Experimental scenarios, e.g., the direction of the density gradients, values of the plasma collision frequency, electron orbits, etc. in a typical POS are discussed.

Research paper thumbnail of Channel length and wall recombination effects in the Hall thruster

36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 2000