Cyclotron Resonance Conditions Research Articles

Influence of the shear flow on electron cyclotron resonance plasma confinement in an axisymmetric magnetic mirror trap of the electron cyclotron resonance ion source

Influence of shear flows of the dense plasma created under conditions of the electron cyclotron resonance (ECR) gas breakdown on the plasma confinement in the axisymmetric mirror trap ("vortex" confinement) was studied experimentally and theoretically. A limiter with bias potential was set inside the mirror trap for plasma rotation. The limiter construction and the optimal value of the potential were chosen according to the results of the preliminary theoretical analysis. This method of "vortex" confinement realization in an axisymmetric mirror trap for non-equilibrium heavy-ion plasmas seems to be promising for creation of ECR multicharged ion sources with high magnetic fields, more than 1 T.

Generation of high charge state metal ion beams by electron cyclotron resonance heating of vacuum arc plasma in cusp trap

A method for generating high charge state heavy metal ion beams based on high power microwave heating of vacuum arc plasma confined in a magnetic trap under electron cyclotron resonance conditions has been developed. A feature of the work described here is the use of a cusp magnetic field with inherent "minimum-B" structure as the confinement geometry, as opposed to a simple mirror device as we have reported on previously. The cusp configuration has been successfully used for microwave heating of gas discharge plasma and extraction from the plasma of highly charged, high current, gaseous ion beams. Now we use the trap for heavy metal ion beam generation. Two different approaches were used for injecting the vacuum arc metal plasma into the trap--axial injection from a miniature arc source located on-axis near the microwave window, and radial injection from sources mounted radially at the midplane of the trap. Here, we describe preliminary results of heating vacuum arc plasma in a cusp magnetic trap by pulsed (400 μs) high power (up to 100 kW) microwave radiation at 37.5 GHz for the generation of highly charged heavy metal ion beams.

Extraction of negative hydrogen ions from a compact 14 GHz microwave ion source

A pair of permanent magnets has formed enough intensity to realize electron cyclotron resonance condition for a 14 GHz microwave in a 2 cm diameter 9 cm long alumina discharge chamber. A three-electrode extraction system assembled in a magnetic shielding has formed a stable beam of negative hydrogen ions (H(-)) in a direction perpendicular to the magnetic field. The measured H(-) current density was about 1 mA∕cm(2) with only 50 W of discharge power, but the beam intensity had shown saturation against further increase in microwave power. The beam current decreased monotonically against increasing pressure.

Self-induced transparency, compression, and stopping of electromagnetic pulses interacting with beams of unexcited classical oscillators

The self-induced transparency effects that emerge when short (on the relaxation time scale) light pulses propagate in a two-level noninverted medium are well known in optics. The interaction of microwave pulses with an initially rectilinear electron beam under cyclotron resonance conditions can serve as a classical analog of the described effects. In this case, at a certain intensity of the input signal, the cyclotron absorption is replaced by self-induced transparency when the input pulse propagates almost without any change of its profile, forming a soliton whose amplitude and duration are rigidly related to its velocity. In a certain domain of parameters, this process is accompanied by significant two- or threefold compression of the initial pulse, which is of practical interest for the generation of multigigawatt picosecond microwave pulses. Since the soliton velocity lies between the unperturbed group velocity of the radiation and the translational velocity of the particles, another nontrivial effect in the case of interaction with a counterpropagating electron beam is the possibility of a significant deceleration or full stopping of the electromagnetic pulse.

Formation of Multicharged Metal Ions in Vacuum Arc Plasma Heated by Gyrotron Radiation

A new method for the generation of high charged state metal ion beams is developed. This method is based on microwave heating of vacuum arc plasma in a magnetic trap under electron cyclotron resonance (ECR) conditions. Two gyrotrons for plasma heating were used, which were with the following parameters. The first is with a wave frequency of 37.5 GHz, a pulse duration of 1 ms and power of 100 kW, another is with 75 GHz, 0.15 ms and 400 kW. Two different magnetic traps were considered for vacuum arc plasma confinement. The first one is a simple mirror trap. Such system was already investigated and could provide high charge state ions. The second trap was with a cusp magnetic field configuration with native “minimum-B" field structure. Two different ways of metal plasma injection into the magnetic trap were used. The first one is an axial injection from an arc source located out of the trap, and the second is a radial injection from four arc sources mounted at the center of the trap. Both traps provide up to 200 eMA of ion beam current for platinum ions with highest charge state 10+. Ion beams were successfully extracted from the plasma and accelerated by a voltage of up to 20 kV.

ON SMALL-SIGNAL AMPLIFICATION IN A GYRO-TWT

The corrected dispersion relation governing the linear interaction of a TE mode in a circular cylindrical wave guide with an annular beam of gyrating electrons in a gyro-TWT conflguration is derived. The derivation of the correct dispersion relation no longer involves any integration with respect to the radial coordinate ro of the electron guiding center as the relevant equilibrium distribution function turns out to be independent of ro. When the cyclotron resonance condition is satisfled by the TE mode for a positive s-number, the small-signal theory is shown to predict an initial exponential growth of the mode with interaction length over a small but flnite band of frequencies around the design frequency.

Non-Equilibrium Heavy Gases Plasma MHD-Stabilization in Axisymmetric Mirror Magnetic Trap

Experimental researches of the shear flows influence on the confinement in the mirror trap of the dense nonequilibrium helium and nitrogen plasma created under conditions of the electron cyclotron resonance (ECR) gas breakdown were made.Limiter with electric potential relative to the vacuum chamber was set inside the mirror trap.During the increasing of the value of limiter potential over Ucrit = 70-100 V the considerable increasing of the full ion flux from the trap was obtained (about of 3-4 times) that is apparently indicates that the plasma density and may be electron temperature increased in the trap that can be interpreted as the transversal losses decrease that is the result of “vortex confinement” regime realization. Pointed effect was obtained in the helium and nitrogen plasma both. Azimuthal modes with m = 1, m = 2 dominated in spatial spectrum of plasma oscillations.This method of “vortex confinement” regime realization for non-equilibrium heavy ions plasmas seems to be perspective for new generation of ECR heavy multicharged ion sources creation.

Self-Induced Transparency and Electromagnetic Pulse Compression in a Plasma or an Electron Beam under Cyclotron Resonance Conditions

Based on analogy to the well-known process of the self-induced transparency of an optical pulse propagating through a passive two-level medium we describe similar effects for a microwave pulse interacting with a cold plasma or rectilinear electron beam under cyclotron resonance condition. It is shown that with increasing amplitude and duration of an incident pulse the linear cyclotron absorption is replaced by the self-induced transparency when the pulse propagates without damping. In fact, the initial pulse decomposes to one or several solitons with amplitude and duration defined by its velocity. In a certain parameter range, the single soliton formation is accompanied by significant compression of the initial electromagnetic pulse. We suggest using the effect of self-compression for producing multigigawatt picosecond microwave pulses.

Formation of a Hot Electron Ring in an ECR Mirror Trap Through a Particle-in-Cell Simulation Study

Plasma structure and electron ring formation in a magnetic mirror trap under electron cyclotron resonance (ECR) conditions is studied numerically through a simulation of the Newton–Lorentz equation by a particle-in-cell method. The plasma self-generated electric field is calculated through a numerical solution of the Poisson equation with the help of the fast Fourier transform technique. The zone where the ECR conditions are fulfilled is almost of a one-sheet hyperboloid shape. It is shown that in the middle transversal plane of the trap, a stable gyrating electron ring is formed. Some trajectories of the hot and superhot electrons comprising the ring are visualized.

Three-Dimensional Particle-In-Cell Simulation of Spatial Autoresonance Electron-Beam Motion

The relativistic dynamics of an electron beam which is accelerated by a circular polarized standing electromagnetic wave in an axisymmetric steady-state magnetic field under cyclotron-resonance conditions is studied. The profile of the inhomogeneous magnetic field is chosen such as to maintain the beam electrons in the space cyclotron autoresonance regime. The influence of the self-consistent field under space-autoresonance conditions is simulated by using the particle-in-cell method. The electric potential produced by electron beams on each time step is found by solving the Poisson equation under the Dirichlet boundary conditions through the fast Fourier transform technique. The axisymmetric magnetic field and the self-consistent electric field are found in the particle positions through bilinear and trilinear interpolations of the mesh node data, which are extensions of the linear interpolation to dimensions D = 2 and D = 3. The beam trajectory and its energy evolution are obtained by solving the relativistic Newton-Lorentz equation employing the Boris leapfrog procedure. The 6-kV/cm TE112 microwave mode of 2.45-GHz frequency is used for the numerical simulations. It is shown that an electron beam of an initial longitudinal energy of 10 keV injected into the axisymmetric magnetic field is found in the resonance phase band, and it is accelerated up to an energy of 0.2 MeV. The main purpose of this paper is to determine the optimum parameters for an electron beam acceleration via the spatial autoresonance mechanism using a numerical modeling.

Calcium Ion Cyclotron Resonance (ICR), 7.0 Hz, 9.2 μT Magnetic Field Exposure Initiates Differentiation of Pituitary Corticotrope-Derived AtT20 D16V Cells

The aim of this work is the study of the effect of electromagnetic radiations (ELF-EMF) tuned to the calcium cyclotron resonance condition of 7.0 Hz, 9.2 μT on the differentiation process of pituitary corticotrope-derived AtT20 D16V cells. These cells respond to nerve growth factor by extending neurite-like processes. To establish whether exposure to the field could influence the molecular biology of the pituitary gland, a corticotrope-derived cells line (AtT20 D16V) was exposed to ELF-EMF at a frequency of 7.0 Hz, 9.2 μT electromagnetic field by a Vega Select 719 power supply. Significant evidence was obtained to conclude that as little as 36 h exposure to the Ca2+ ICR condition results in enhanced neurite outgrowth, with early expression and aggregation of the neuronal differentiation protein NF-200 into neurite structures.

Heating and deceleration of minor ions in the extended fast solar wind by oblique Alfvén waves

Using one‐dimensional hybrid simulations, the interaction between oblique propagating Alfvén waves and minor ions in the fast solar wind stream is investigated in this paper. In typical fast solar wind conditions, these waves and the drifting minor ions satisfy the ion cyclotron resonance condition: ω = −Ωi + k∥v∥. (Here ω is the wave angular frequency, Ωi is the gyration frequency of an ion species i, k∥ is the wave number component along the background magnetic field B0, and v∥ is the particle velocity component of the ion species parallel to B0.) These waves are able to heat minor ions while decelerating them at the same time. The heating is primarily in the direction perpendicular to the background magnetic field, and the deceleration helps to restrict minor ion and proton beam‐drifting speed at or just lower than the local Alfvén speed (in relative to the speed of the core proton component).

Design, fabrication, and characterization of a solenoid system to generate magnetic field for an ECR proton source

Solenoid coils with iron jacket (electromagnets) have been designed and developed for generation and confinement of the plasma produced by an electron cyclotron resonance source operating at 2450MHz frequency. The magnetic field configurations designed using the solenoid coils are off-resonance, mirror, and flat, satisfying electron cyclotron resonance condition along the axis of the plasma chamber. 2D Poisson software was used for designing. Details of design, fabrication, and magnetic field mapping of the solenoid coils are presented in this paper.

Transient magnetoresponse of photoexcited electrons: Negative cyclotron absorption and evolution of Faraday angle

The transient magnetooptical response of electrons with partly inverted initial distribution produced by an ultrashort optical pulse near the optical phonon energy is studied theoretically. Transient cyclotron absorption and Faraday rotation of polarization plane are considered for bulk semiconductors (GaAs, InAs, and InSb) as well as for a GaAs-based quantum well. Damping of the response due to electron momentum relaxation associated with elastic scattering from acoustic phonons is taken into account in calculations, as well as the evolution of the electron distribution due to quasi-elastic energy relaxation at acoustic phonons and effective inelastic transitions accompanied by spontaneous emission of optical phonons. Nonstationary negative absorption in the cyclotron resonance conditions and peculiarities of Faraday rotation of the polarization plane associated with partial inversion of the initial distribution are considered. The possibility of transient enhancement of the probe field under cyclotron resonance conditions is indicated.

Parametric generation of low-frequency waves by plasma electrons accelerated under electron cyclotron resonance conditions

It has been shown experimentally that the diamagnetic effect appearing when electrons of a magnetized plasma in the antenna near field are accelerated under electron cyclotron resonance conditions can be used to generate low-frequency waves. The amplitude modulation of a signal supplied to the antenna is accompanied by the modulation of the diamagnetic effect and leads to the emission of waves at the modulation frequency to the surrounding plasma. In this process, the extended plasma region containing accelerated electrons serves as a parametric bodiless antenna. The results of the model laboratory experiments make it possible to propose a method for the parametric generation of low-frequency whistler waves in the Earth’s ionosphere by a powerful amplitude-modulated signal supplied to the satellite-borne antenna.

10.1007/s11454-008-1001-x

Interaction between the thermal fluctuation electromagnetic field of a condensed medium and a weak external factor, say, a weak effective magnetic field including an external magnetic field, rigid rotation of the medium, and Coriolis force, imparts a torque to any charged free or bound particles (atoms, molecules, etc.). which indicates that the medium is sensitive to weak actions. The torque is proportional to thermal energy kT and may increase substantially under the cyclotron resonance conditions. The so-called kT problem is solved, so that many observations having to do with the field of physics that can be called the physics of weak actions (≪kT) can now be theoretically explained.

Comparisons of Electron Temperature and Density, and Ion Temperature Profiles in the TJ-II Stellarator

Charge exchange-neutral particle analyzer diagnostics are used to obtain majority ion temperature profiles for plasmas created in the TJ-II stellarator. However, because of technical limitations, measurements are limited to two radial positions per discharge. Therefore plasma reproducibility for a large number of discharges is essential for performing scans across the plasma minor radius and hence for obtaining ion temperature profiles. Such conditions have recently been achieved in the TJ-II by the implementation of a lithium wall coating which has significantly facilitated this task. In this paper, ion temperature profiles obtained under electron cyclotron resonance (ECR) and neutral beam injection (NBI) plasma heating conditions are compared with electron temperature and density profiles obtained using a Thomson Scattering diagnostic. From this, similarities in the forms of the ion temperature and electron density profiles are noted for ECR heated plasmas whilst for NBI heated plasmas similarities are observed between ion temperature and electron temperature profiles. Finally, after explaining the different behaviours of the profiles in terms of ion power absorption profile, we demonstrate the possibility of determining ion temperature profiles using two localized ion temperature measurements plus Thomson Scattering profiles.

Transient Magnetoresponse of Photoexcited Electrons: Oscillating Conductivity and Negative Cyclotron Absorption

The nonlinear transient magnetoresponse of two-dimensional (2D) electrons is studied theoretically. Transient conductivity is calculated under exact cyclotron resonance condition. Two cases are considered: (a) the electrons excited by an ultrashort optical pulse, and isotropy of the initial distribution is expected; (b) dc electric field impose strongly anisotropic initial distribution. In case (b), evolution is strongly dependent on the initial phase of a circularly polarized wave. After the streaming distribution is formed, the magnetoresponse demonstrates periodically oscillating conductivity for both cases. The negative cyclotron absorption caused by the transient absolute negative conductivity effect is predicted for a certain range of parameters.

Influence of Shubnikov de Haas and cyclotron resonance effect on terahertz detection by field effect transistors

AbstractExperiments on terahertz radiation detection with InGaAs/InAlAs field‐effect transistor in quantizing magnetic field are reported. We observed oscillations of the photovoltaic signal analogous to Shubnikov‐de Haas oscillations, as well as their strong enhancement at the cyclotron resonance conditions. The results are described quantitatively within the frame of a theory which takes into account a new source of nonlinearity related to the Landau quantization of the conduction band. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Plasma waves Terahertz detection by field effect transistor in Quantinzing magnetic fields

Detection of THz radiation by a Field Effect Transistor InGaAs/InAlAs transistor was investigated at 4.2 K as a function of the magnetic field and gate voltage. We observed oscillations of the photovoltaic signal analogous to Shubnikov-de Haas oscillations, as well as their strong enhancement at the cyclotron resonance conditions. The results are successfully quantitatively described within the frame of a recent theory, taking into account a new source of nonlinearity related to Shubnikov-de Haas effect. We show that the detection is due to gated plasmon.