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A recent event study suggested a coupling process whereby suprathermal protons (10–100 eV), as a result of perpendicular heating by pre-existing magnetosonic waves, can excite electromagnetic ion cyclotron (EMIC) waves with frequency near the local proton cyclotron frequency ( f ~ 0.95 f cp ). The present study tests this coupling process. First, one-dimensional hybrid (kinetic ions/massless fluid electrons) simulations of parallel-propagating EMIC waves initialized with the plasma conditions derived from the event prove that high frequency EMIC waves can be generated by anisotropic suprathermal protons instead of more energetic (10s of keV) ring current protons. Calculation of the quasilinear pitch-angle diffusion coefficient for electrons using the simulated waves suggests that these high frequency EMIC waves outside the plasmasphere can play a role in the pitch-angle scattering of ~ MeV electrons due to the large wavenumber of the excited EMIC waves. Second, the role of the pre-existing magnetosonic waves in the suprathermal proton heating is examined using quasilinear diffusion theory and simple test particle calculation. It is found that the quasilinear diffusion becomes ineffective in energies relevant to the suprathermal protons, indicating that the low-energy ( 10 eV) protons cannot be efficiently energized to the observed level through multi-harmonic cyclotron resonances with the magnetosonic waves observed. Rather, some kind of non-resonant process may have been at play, if the magnetosonic waves were actually involved in the heating. This result suggests that more quantitative understanding of the suggested energy coupling process through magnetosonic waves is needed.

The solar wind plasma is characterized by unequal effective kinetic temperatures defined in perpendicular and parallel directions with respect to the ambient magnetic field. For electrons, the excessive perpendicular temperature anisotropy leads to quasi-parallel electromagnetic electron cyclotron (or whistler) instability and aperiodic electron-mirror instability with oblique wave vectors. The present paper carries out a direct side-by-side comparison of quasi-linear (QL) theory and particle-in-cell (PIC) simulation of combined mirror and cyclotron instabilities acting upon the initially anisotropic electron temperatures, and find that the QL theory satisfactorily encapsulates the non-linear aspect of the combined instability effects. However, a discrepancy between the present study and a previous PIC simulation result is also found, which points to the need for further investigation to resolve such an issue.

It is shown that ions can be accelerated to about 100 keV in the direction perpendicular to the magnetic field by the ExB mechanism of electrostatic waves. The acceleration occurs in discrete steps of duration being a small fraction of the gyroperiod and can explain observations of ion energization to 10 keV at quasi-perpendicular shocks and to hundreds keV at quasi-parallel shocks. A general expression is provided for the maximum energy of ions accelerated in shocks of arbitrary configuration. The waves involved in the acceleration are related to three cross-field current-driven instabilities: the lower hybrid drift (LHD) instability induced by the density gradients in shocks and shocklets, followed by the modified two-stream (MTS) and electron cyclotron drift (ECD) instabilities, induced by the ExB drift of electrons in the strong LHD wave electric field. The ExB wave mechanism accelerates heavy ions to energies proportional to the atomic mass number, which is consistent with satellite observations upstream of the bow shock and also with observations of post-shocks in supernovae remnants. The results are compared with other acceleration mechanisms traditionally discussed in the literature.

The electron cyclotron heating (ECH) and current drive system is one of the main plasma heating systems for ITER. It uses high-power microwave beams with the power deposition location steerable acr...

A 500 GHz TE85 mode continuously frequency-tunable gyrotron has been designed, fabricated and investigated experimentally. In the experiment, the gyrotron operates at the second cyclotron harmonic stably. The operating frequency is tuned by means of adjusting the operating magnetic field or the beam energy. The variation of the output power is also investigated. It is found that when the operating magnetic field is changed, the frequency-tuning range is much bigger than that when the beam energy is changed.

The dependence was studied of the level of density fluctuations recorded at different devices on the minor and major radii of the tokamak. It is known that a high level of density fluctuations can negatively affect the operation of diagnostics, in particular, the plasma reflectometry diagnostic. The increase of density fluctuations decreases the quality of raw data by increasing the error of measuring the density profile and, when density fluctuations exceed the threshold value, it renders such measurements impossible. Based on experimental data obtained on devices with substantially different sizes, a dependence of the density fluctuation level on the major and minor tokamak radii was proposed. Since the main experiments were carried out in round limiter tokamaks in ohmic (OH) heating regimes, the extrapolation result is applicable, generally speaking, to installations of larger size with the same configuration and regimes. However, experiments with electron cyclotron heating at the T-10 tokamak also allow one to extend the obtained dependence to regimes with auxiliary heating. It was shown that the obtained dependence is applicable to limiter tokamaks Tore Supra and TFTR of larger size. The applicability of the dependence to installations with diverter configuration is discussed and the possible level of density fluctuations is extrapolated to the international reactor tokamak ITER that is being constructed in France.

In this paper, we calculated the radiation from the state where an electron in cyclotron motion under the uniform magnetic field Bex was accelerated by the externally applied circularly polarized wave with strong Ein and Bin. The electron was accelerated in the parallel direction by the term β⊥ × Bin (β⊥: perpendicular velocity of the electron) as well as in the perpendicular direction by the electric field of the wave Ein. Then, the electron can be resonantly accelerated when the Bex is set to the magnetic field strength which is equivalent to frequency of the externally applied circularly polarized wave. The radiation from such an accelerated electron was confirmed to have helical wavefront at harmonics cyclotron frequency.

We propose a novel source of high-power 1–3-THz radiation based on frequency multiplication in a planar gyrotron, with transverse energy extraction. In such a scheme, it is possible to increase significantly the transverse size both of the cavity and of the electron beam, and, correspondingly, the output power at the fundamental harmonic. At the same time, equidistant mode spectrum of a cavity of planar gyrotrons is favorable for generation at high-order cyclotron harmonics in the frequency multiplication regime, providing a much higher efficiency of nonlinear conversion when compared with conventional cylindrical gyrotron schemes. In simulations of a 1-THz planar gyrotron, within the multimode time-domain model, we demonstrate a possibility of kilowatt-level radiation at the second cyclotron harmonic and power of several watts at the third one. The obtained results are partially confirmed based on direct 3-D particle-in-cell (PIC) simulations.

The correlation between the parameters of electromagnetic ion cyclotron waves in Earth’s magnetosphere and the parameters of trapped and precipitating ring current ions is analyzed using the example of a single event. It is shown that the observed energies and the degree of isotropy of proton fluxes at low altitudes correspond to the results from calculating the coefficient of pitch-angle diffusion using data on ion cyclotron wave parameters.

Influence of a longitudinal stationary current on the absorption and the radial structure of fast waves in a cylindrical current-carrying plasma is discussed. To evaluate the dispersion equation for fast waves, there was used the dielectric tensor taking into account the radial current structure and geometry of the confining helical magnetic field by the plasma safety factor. It is shown that the damping rate of fast waves in a non-equilibrium current-carrying plasma differ from those for an equilibrium plasma column in a homogeneous magnetic field nearby the cutoffs and resonances due to the rotational transformation (including shear-effects) of the helical magnetic field lines.

An investigation is performed of the relaxation of plasma excitations in two-dimensional electron systems (2D-ESes) in GaAs/AlGaAs heterostructures. The effect radiational and incoherent collisional relaxation mechanisms have on the linewidth of cyclotron magnetoplasma resonance (CR) is studied. CR arises as a pure resonance that does not hybridize with dimensional magnetoplasma excitations. It is shown how magnetoplasma resonances form a CR’s fine structure due to the interaction between coherent radiative and incoherent collisional mechanisms of two-dimensional plasma relaxation. A comparative analysis is performed of the dependences of cyclotron and transport periods of relaxation on both the temperature and electron density of 2D-ESes. It is demonstrated that the period of cyclotron relaxation could exceed that of transport at low electron densities.

The parametric decay instability of microwaves with extraordinary polarization is analyzed that leads to their anomalous scattering by oscillations of the intermediate frequency range, localized in the edge transport barrier of a fusion installation. This effect can occur during electron cyclotron heating of the plasma at the second harmonic of the resonance frequency by multi megawatt microwave beams.

This is a study of drift waves in the electron-positron plasma of the magnetosphere of a pulsar. It is shown that the nonlinear interaction of the drift waves with the plasma particles leads to the formation of small-scale structures. The cyclotron instability which develops in these structures may be the reason for the formation of the nano-outbursts discovered in the radio emission of a pulsar in the Crab nebula.

Terahertz (THz) radiation from a plasma cylinder with embedded radial electric and axial magnetic fields is investigated. The plasma density and the electric and magnetic fields are such that the electron plasma frequency is near the electron cyclotron frequency and in the THz regime. Two-dimensional particle-in-cell simulations show that the plasma electrons oscillate not only in the azimuthal direction but also in the radial direction. Spectral analysis shows that the resulting oscillating current pattern has a clearly defined characteristic frequency near the electron cyclotron frequency, suggesting resonance between the cyclotron and plasma oscillations. The resulting far-field THz radiation in the axial direction is also discussed.

A method of improving the selectivity of open cavities of electron cyclotron masers (gyrotrons) operating at high cyclotron harmonics in the terahertz frequency range is proposed and described. This method is purely electrodynamical and based on a simple deformation of the cavity wall. The proposed approach paves the way for the increase in the gyrotron frequencies and for enhancing the selectivity of open cavities in other applications.

This paper presents a conceptual design of the compact SC230 superconducting cyclotron that accelerates a beam of protons to 230 MeV and is intended for proton therapy and biomedical research. SC230 is an isochronous four-sector cyclotron based on a shell-type magnet with a magnetic field in the center of 1.7 T. Superconducting coils will be enclosed in a cryostat; all other parts of the cyclotron are warm. Acceleration is carried out at the fourth harmonic mode of the accelerating high-frequency (HF) system consisting of four resonators located in the cyclotron valleys. The accelerator employs an internal Penning-type hot cathode source. Extraction is carried out using an electrostatic deflector located in the gap between the sectors and two passive magnetic channels.

In Fourier-transform ion cyclotron resonance mass spectrometry, ions are detected by measuring image current induced in the detecting electrodes by trapped ions rotating in a magnetic field at their cyclotron frequencies. The ion trap used for this purpose is called the Penning trap. It can have various configurations of electrodes that are used to create a trapping electric field, to excite cyclotron motion, and to detect the induced signal. The evolution of this type of mass spectrometry is mainly driven by progress in the technology of superconducting magnets and in the constantly improved design of the ion cyclotron resonance (ICR) measuring cell. In this review, we focus on ICR cell designs. We consider that the driving forces of this evolution are the desire to increase resolution, mass accuracy and dynamic range, as well as to adapt new methods for creating and trapping ions.

The dispersion relation of a new electrostatic ion cyclotron (IC) instability of a plasma with a sheared current of the oxygen ions along the magnetic field is investigated analytically and solved by numerical analysis. The considered case corresponds to the upward sheared flow of the oxygen ions in the aurora where the velocity shearing rate of ion current may be larger than the cyclotron frequency of O+ ion. In such a plasma, we found a new instability in the IC frequency range which develops in the sheared flow and can have a growth rate larger than O+ cyclotron frequency. This instability develops jointly with the known IC instability for the uniform current with a growth rate much less than O+ cyclotron frequency

The study is continued of the temporal changes of the parameters of turbulent plasma density fluctuations during multi-pulse electron cyclotron (EC) heating of the plasma on the L-2M stellarator. The plasma density fluctuations with different wave vectors (k = 30, 20, 2, and 1 cm –1) in different spatial regions of the plasma column were recorded by the method of collective scattering of microwave radiation. The time dependence of plasma density fluctuations, which has a bursty shape, was analyzed, including the discharges in which the gyroresonance region was shifted by 3–4 cm from the center of the plasma column toward the inside of the torus. A comparison was made between the specificities of the evolution of plasma density fluctuations and the evolution of their statistical characteristics. It was found that the kurtosis (M4) of the scattering signals deviates from the value 3, which also occurs in bursts. During a EC heating pulse, three groups of different bursts (of signal intensity, its kurtosis and their increments) were observed. Autocorrelation analysis of density fluctuations and their increment was carried out and it showed that the half-width of the autocorrelation functions changes during multi-pulse EC heating. The probability of the initiation of bursty processes by perturbations in the near-wall plasma region is discussed.

Based on the analysis of electron–wave interaction, we study the possibility of developing a gyrotron that is able to provide a megawatt output power in quasi-continuous (long-pulse) oscillations at both first and second gyrofrequency harmonics. For selective excitation at the second cyclotron harmonic when the operating current is significantly higher than its starting value, we propose to lock the gyrotron by a weak (several percent power) monochromatic incoming signal which suppresses spurious oscillations at the fundamental cyclotron resonance in the gyrotron start-up process. Simulations of a two-frequency gyrotron with an output power of 1 MW at the first cyclotron harmonic (19 GHz) and 0.8 MW at the second one (38 GHz) based on a nonstationary self-consistent system of equations are presented. Such a source of radiation is of interest for plasma-heating systems in spherical tokamaks.

Coherent subterahertz radiation in the continuous-wave regime was obtained in a large-orbit gyrotron (LOG) operated at a high harmonic of the cyclotron frequency. An electron–optical system containing a gun with a cusp followed by a section of adiabatic magnetic compression with a factor of 1000 ensures the formation of a 30 keV/0.7 A helical axis-encircling electron beam with acceptable velocity spread and pitch factor in a magnetic field of 5 T. Stable singlemode operation was obtained at frequencies of 0.394 and 0.267 THz with radiation powers of 0.37 and 0.9 kW at the third and second cyclotron harmonics, respectively. Tuning of the generation frequency in the gyrotron during its operation at the second cyclotron harmonic and complex regimes of competition of two waves excited at the second and third cyclotron harmonics are also studied.

A numerical calculation to study the effect of laser pulse polarization on the strength of the axial wakefield in a magnetized plasma has been presented. The influence of different laser polarization, including linear (ordinary wave), elliptic (extraordinary wave), and right- and left-hand circular polarization on the wake wave amplitude, has been evaluated for various values of laser and plasma frequency at a fixed cyclotron frequency. Comparing the results, it is found that an extraordinary laser wave can excite the largest wake wave amplitude. The upper-hybrid wakefield is in the order of $E_{w}\approx 70~$ GV/m, which, under appropriate conditions, is generated by an elliptic Gaussian laser pulse with a relatively low intensity ( $a_{0}=0.3$ ).

A plasma with an anisotropic velocity distribution of particles in a magnetic field is considered. It is shown that the Weibel instability arises in the reference frame rotating together with the particles, for example, ions. When considered in the immobile reference frame, this instability is known as the Alfvén cyclotron instability.

A method of increasing the selectivity of highly-oversized open cavities is experimentally demonstrated in the electron cyclotron maser (gyrotron) operating at the second cyclotron harmonic in a high transverse mode (presumably, TE58,13) of a circular cylindrical cavity at a frequency near 1.2 THz in the magnetic field of 24 T. This method is purely electrodynamical and based on a simple deformation of the cavity wall. The proposed approach paves the way for increase of the gyrotron frequencies and for enhancing the selectivity of open cavities in other applications.

The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) is a linear device used to develop the source and heating concept for MPEX, an experiment to study plasma–material interactions for future fusion reactors. This article will highlight recent analysis and results on Proto-MPEX using an infrared (IR) camera, a key tool for imaging heat fluxes measured at the material target. The target heat fluxes are crucial to understanding the source and heating concepts. The recent analysis includes the application of homography and 3-D finite-element methods to provide between-shot measurements of the 2-D target heat flux profile. The IR camera inferred heat flux is shown to correlate with Langmuir probe inferred heat fluxes for a range of parameters in helicon only and helicon + electron cyclotron heated discharges. Results show both desirable central and undesirable edge heat flux for helicon source and electron heating on the target. These heat flux measurements are shown to be important for better understanding of the source and heating physics.

In this article, the time-dependent multimode competition equations, the dependence of the starting current on the static magnetic field, and the current ratio of a coaxial cavity gyrotron with multiple electron beams are investigated according to the linear and nonlinear theories. By numerical calculation, the mode competition of a 170-GHz coaxial cavity gyrotron is studied when it has one, two, and three electron beams. Researches demonstrate that under the given magnetic field $B$ , electron beam voltage $U$ , and pitch factor ${\alpha }$ , a gyrotron with different electron beam numbers has different startup scenarios, which show that the gyrotron with three electron beams has potential in the selection of mode, the depression of mode competition, and the increase of output power. Results find that the coaxial cavity gyrotron with three electron beams can operate steadily in the ${\text {TE}_{38,18-}}$ mode at 170.39 GHz and it has an output power of 5.02 MW and a beam–wave interaction efficiency of 35.42% when $B=6.82\text{T}$ , $U=88$ kV, $\alpha =1.3$ , $I=158$ A and the three electron beams locate at 11.14, 12.93, and 14.32 mm. Three electron beams in the gyrotron have different beam–wave interaction efficiencies, and the closer the electron beam is to the inner conductor, the higher its beam–wave interaction efficiency is.

The mechanism that the author’s recently developed for plasma fusion at kiloelectron volts (keV) has been extended from the D-3He fusion with extremely heated 3He ions to the D-T fusion with extremely heated tritons. Two major significances of this extension are that the D-T fusion has the highest reactivity and the plasma does not need H ions, which do not participate in the fusion, because the plasma needs only to generate current-driven electrostatic D-cyclotron (CDEDC) waves for the extra heating of tritons rather than current-driven electrostatic H-cyclotron (CDEHC) waves for the extra heating of 3He ions. The extended mechanism works in a two-stage heating process when an electric current is driven through plasma that contains deuterons and tritons. First, the current ohmically heats the plasma up to some keV, at which the resistivity in the plasma is too low for the current to be significantly dissipated further. When the electric current is continuously driven up to a critical point, however, CDEDC waves are excited, which can preferentially heat tritons via the second-harmonic resonance further to tens of keV or higher, at which the nuclear fusion between the extremely heated tritons and the relatively cold deuterons occurs. In addition, this mechanism can greatly reduce technology and engineering difficulties in plasma control and confinement. This article also develops a new anisotropic model for plasma heating by ion-cyclotron waves and indicates that ions are mainly heated perpendicularly via the cyclotron resonances, while electrons are mainly heated in parallel via the Landau resonance.

Many conventional experimental analyses have helped us to understand most of the properties of plasma wave interactions and its behavior; nonlinear dynamics has helped us to enhance our analysis. In this paper we have tried to analyze a plasma jerk system for an ion cyclotron plasma oscillation in a magnetic field by including a higher-order source term caused by large-amplitude fluctuations. The multistability and antimonotonicity properties of the plasma system are discussed which were not explored earlier. We have also shown that the large-amplitude limit cycle in the original jerk system model of plasma is now reduced to a much smaller chaotic cycle for the new proposed system with higher-order source term.

The Prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory is developing a helicon radio frequency (RF) source for plasma production along with microwave electron heating and RF ion heating. Proto-MPEX has several magnetic mirrors that affect plasma transport. The magnetic field near the helicon source is ~ 0.05 T, and the peak magnetic field in Proto-MPEX is ~ 1.8 T, which results in a large magnetic well for particles sourced at the helicon transporting toward the target region. Keeping the helicon source field and the target field constant, experiments have been conducted by methodically changing the magnetic field, at a local axial location, within the source and the target. Plasma flow measurements using Mach probes have shown a decrease in the flow as a function of the magnetic mirror ratio. Plasma flows were further investigated with ion cyclotron resonant heating (ICH). Results with the addition of ICH measured upstream of the antenna have shown a decrease in Mach number as a function of mirror ratio when compared to helicon discharges. Such flow behavior demonstrated slowing down of the plasma due to the increased reverse plasma flow toward the helicon plasma source. However, in high magnetic fields, when the resonant magnetic field moved away from the ICH antenna, no effects on the plasma flow due to ICH were observed.

To enhance parameters of the plasma and improve the magnetic confinement performance, a 105-GHz electron cyclotron resonance heating (ECRH) system is being built on the J-TEXT. We designed a quasi-optical launcher which mainly consists of a focusing mirror and a steering mirror. The focusing mirror is optimized by considering the localized deposition, and the steering mirror is close to the plasma boundary for flexible adjustment of the toroidal and poloidal injection angles of the wave. The toroidal and poloidal rotation angles of the steering mirror are independently controlled by the mechanical structure. For our design, the beam radius at the plasma center for perpendicular incidence is about 20 mm; the adjustable range of the toroidal and poloidal injection angles is ±14° and ±31°, respectively. These can meet the requirements for physics experiments on J-TEXT.

With allowance for the centrifugal and gradient drifts of ions, a new approximate dispersion equation is obtained for the ion Bernstein (IB) wave propagating strictly transverse to the external inhomogeneous magnetic field. Using this equation, it is shown that if, in the high-temperature plasma, the drift of ions is taken into account, the resonance frequency ranges in the vicinities of the ion cyclotron frequency harmonics can strongly overlap. In this case, the ion Bernstein waves turn out to be strongly damped, despite the absence of the longitudinal component of the wave vector.

We propose a robust way of advancement of the gyrotrons into the region of terahertz frequencies and MW-level power of radiation while retaining high efficiency and high stability of the frequency. These gyrotrons may be used for electron cyclotron resonance heating and current drive systems (ECRH&CD) in future fusion setups, in large complexes of coherently radiating gyrotrons for THz data and energy transmission, for THz particles acceleration. We at first demonstrate the advantages of this way at the example of the gyrotron with very-high-order operating mode TE56.24, driven by a relatively weak external monochromatic signal, and show that in the phase- and frequency-locking mode a significant enhancement of radiation parameters – frequency, power and efficiency – can be achieved.

The generalized expression for the Bernstein waves in the nonrelativistic limit is analyzed for pair ion plasma with the contribution of electrons. The effect of temperature and mass asymmetry on the propagation of the Bernstein waves is studied in detail. It is observed that due to asymmetry an extra curve exists below the lower harmonics. When we include electrons in pair ion plasma, we observe that the electron temperature affects the propagation of these waves.

The NSCL has successfully used linear gas stopping cells for more than a decade to slow down near-relativistic projectile fragments to energies of tens of keV; first for experiments at low energy and later for reacceleration to Coulomb-barrier energies. In order to stop and rapidly extract light and medium-mass fast ions, which are difficult to efficiently thermalize in linear gas cells, a gas-filled, reverse cyclotron has been constructed. The device uses a cyclotron-type magnet and helium gas in a liquid-nitrogen (LN) cooled stopping chamber to confine and slow down the injected beam. The stopped ions are transported to the center of the magnet by an RF-carpet system, extracted axially through the bore with an ion conveyor and accelerated to For magnet commissioning and low-energy ion tests, the cyclotron gas stopper was constructed in a location that did not allow connection to the NSCL high-energy beamlines. However, all other components have been installed for the device. Efficient ion transport has been demonstrated with ions from a movable alkali source with the magnet energized. An experimental vault is being prepared to allow the connection of the cyclotron gas stopper to the NSCL beamline. The design for a dedicated momentum-compression beam line, similar to the ones feeding the existing linear gas cells [1] , [2] , is complete and the components are under construction. Offline tests have ended and moving the cyclotron stopper to its destination has begun.

An important challenge in plasma physics is to determine whether ionized gases can be confined by strong magnetic fields. After properly formulating the model, this question leads to a penalized version of the Relativistic Vlasov Maxwell system, marked by the role of a singular factor e −1 corresponding to the inverse of a cyclotron frequency. In this paper, we prove in this context the existence of classical C 1-solutions for a time independent of e. We also investigate the stability of these smooth solutions.

The Beijing Radioactive ion beam facility Isotope Separator On-Line (BRISOL) is a radioactive ion beam facility based on a 100 MeV cyclotron providing 200 μA proton beam bombarding the thick target to produce radioactive nuclei, which are transferred into an ion source to produce singly charged ion beams. In order to improve the ionization efficiency for alkali metals, an innovative ion source with the ability of dual ionization mode, including surface ionization mode and FEBIAD ionization mode, was developed. The design and results of this ion source will be presented in this paper.

In this paper we show that two significant phenomena of magnetospheric chorus emission can be explained by the participation of beam-like electron structures, created by Landau-resonant interaction with growing oblique whistler waves. The first concerns the widely observed spectral gap near half the electron cyclotron frequency Ωe; the second is related to the observation of very obliquely propagating lower-band waves that cannot be directly generated by temperature anisotropy. Concerning the gap, kinetic dispersion theory reveals that interference of the beam-related cyclotron mode ω~Ωe-kVb with the conventional whistler mode leads to mode splitting and the appearance of a ‘forbidden’ area in the ω-k space. Thereby the beam velocity Vb appears as an essential parameter. It is directly related to the phase velocity of the most unstable whistler wave mode, which is close to VAe/2 for sufficiently hot electrons (VAe is the electron Alfven velocity). To clarify the second point, we show that Landau-resonant beams with Vb < VAe/2, which arise in cold plasmas from unstable upper-band waves, are able to generate lower-band whistler mode waves at very oblique propagation (θ ≥ 60°). Our studies demonstrate the important role of Landau-resonant electrons in nonlinear whistler wave generation in the magnetosphere.

Increased interest in the development of negative ions sources is related to the emergence of important applications of negative-ion beams. These are, first of all, tandem accelerators, high-energy implantation and accelerator-based mass spectrometry, supercollimated beams, charge-exchange injection into cyclic accelerators and storage rings, charge-exchange extraction of beams from cyclotrons, injectors of high-energy neutrals in plasma systems, and charge-exchange beam separation. The development of sources of negative ions and their use in academic research and industry are reviewed. Physical bases and designs of surface-plasma sources of negative ions, as well as the history of their development, are presented.

The systematization of experimental data related to development of the parametric decay instability in tokamak plasma during RF power input within the lower hybrid frequency range was performed, which allows its characteristics to be compared with theoretical representations. The spectra of pumping waves and radiation from the plasma are obtained, which illustrate the appearance of satellites that are shifted from a pump frequency by a value that is a multiple of the ion cyclotron frequencies, toward the “red” and “blue” sides. It is noted that with a rise in density, a considerable broadening of the line of a pumping wave occurs. Values of the RF power and plasma density are observed, which are threshold values for the onset of the development of parametric decay instability. Using the diagnostic complex, the analysis of the low-frequency region of the plasma oscillation spectrum was carried out. The conditions of the development of instability were analyzed within the existing theoretical representations.

The cold plasmaspheric plasma, the ring current and the radiation belts constitute three important populations of the inner magnetosphere. The overlap region between these populations gives rise to wave-particle interactions between different plasma species and wave modes observed in the magnetosphere, in particular, electromagnetic ion cyclotron (EMIC) waves. These waves can resonantly interact with multiple particle species, being an important loss process for both ring current ions and radiation belt electrons, as well as a cold plasma heating mechanism. This mini-review will focus on the interaction between EMIC waves and cold and thermal plasma, specifically the role of EMIC waves in cold and thermal electron and ion heating. It will discuss early theoretical results in conjunction with numerical modelling and recent satellite observations, and address outstanding problems and controversies in this field.

We report observations of electromagnetic emissions at electron cyclotron harmonics in a mirror-confined electron cyclotron resonance (ECR) plasma. The present research has achieved a new understanding of electron cyclotron instabilities by comparing measurements of emissions from a well-diagnosed laboratory plasma, with the predictions of analytical theory supported by Vlasov simulations. The presence of multi-component electron distribution functions involving a warm and ring-distributed 1 200-400 eV mirror-confined population of electrons and a much colder 1 eV component lead to electrostatic electron cyclotron instabilities and results in microwave emissions. This results have relevance many areas where electron cyclotron instabilities are of fundamental importance, including astrophysical plasmas 2 , near-Earth solar-terrestrial plasmas 3 , laboratory tokamak and stellarator fusion plasmas and electron cyclotron resonance sources.

Observations of proton density fluctuations of the solar wind at 1 au have shown the presence of a decade-long transition region of the density spectrum above sub-ion scales, characterized by a flattening of the spectral slope. We use the proton density fluctuations data collected by the BMSW instrument on-board the Spektr-R satellite in order to delimit the plasma parameters under which the transition region can be observed. Under similar plasma conditions to those in observations, we carry out 3D compressible magnetohydrodynamics (MHD) and Hall-MHD numerical simulations and find that Hall physics is necessary to generate the transition region. The analysis of the kω power spectrum in the Hall-MHD simulation indicates that the flattening of the density spectrum is associated with fluctuations having frequencies smaller than the ion cyclotron frequency.

Theoretical and experimental investigations on a frequency-tunable terahertz gyrotron have been presented in this paper. The effects of the slightly up-tapered sections in an improved multi-section gyrotron cavity on the resonant frequency and the quality factor are investigated in detail. In an optimized multi-section gyrotron cavity, the quality factor for all axial modes can maintain an order of magnitude in the cold cavity approximation, it means that the operating current for all axial modes can keep an order of magnitude. A resonator-based gyrotron oscillator can play dual functions: gyromonotron and reflected-type gyro-BWO corresponding to forward-wave and backward-wave operation. the field profile of the axial mode and beam-wave interaction efficiency of the gyromonotron and the reflected-type gyro-BWO are dramatically different from each other. And the gyromonotron state can switch to the reflected-type gyro-BWO state by means of increasing the operating magnetic field. A 263GHz frequency-tunable gyrotron at the fundamental cyclotron harmonic for the 400MHz DNP/NMR spectroscopy and a 527GHz frequency-tunable gyrotron at the second cyclotron harmonic for the 800MHz DNP/NMR spectroscopy are experimentally investigated.

A compact neutron spectrometer based on the BC-501A liquid organic scintillator was applied to neutron measurements at the TUMAN-3M tokamak. The spectrometer was calibrated using measurements from the ion beam of the cyclotron accelerator. Neutron spectra were measured during discharges using a neutral deuterium beam injection into the TUMAN-3M D-plasma. An energy distribution of the neutrons from the plasma that hit the spectrometer was obtained from the measured BC-501A instrumental spectra by the DeGaSum code using detector response functions obtained in the course of the calibration. This allowed for the estimation of the 2.45 MeV neutron yield and the evaluation of both the time evolution of the DD fusion rate and the characteristic time of the injected deuterium slowing down in discharges with neutral beam injection heating.

In the GAMMA 10/PDX tandem mirror, plasma with strong ion-temperature anisotropy is produced by using the ion cyclotron range of frequency waves. This anisotropy of ion temperature causes several Alfven-Ion-Cyclotron (AIC) waves to spontaneously excite in the frequency range just below the ion cyclotron frequency. In addition, difference-frequency (DF) waves are excited in the radial inner region of the plasma by wave–wave coupling among the AIC waves. The radial density profiles were measured at multi-axial positions using a frequency-modulation reflectometer with an axial array of microwave antennas, and an axial variation of the density was found to be significant. In addition, a relative phase difference of the DF wave between axially separated two points was first obtained by finely choosing the probing frequency of the reflectometers with a maximum coherence used as a measure, indicating that the DF wave is a propagating wave, while the pump AIC waves are standing waves in the axial region of measurement.

The modulational instability of ion-acoustic waves (IAWs) in a four-component magneto-plasma system consisting of positive–negative ions fluids and non-Maxwellian (r,q) distributed electrons and positrons, is investigated. The basic system of fluid equations is reduced to a three-dimensional (3D) nonlinear Schrödinger Equation (NLS). The domains of the IAWs stability are determined and are found to be strongly affected by electrons and positrons spectral parameters r and q and temperature ratio Tp/Te (Tp and Te are positrons and electrons temperatures, respectively). The existence domains, where we can observe the ion-acoustic rogue waves (IARWs) are determined. The basic features of IARWs are analyzed numerically against the distribution parameters and the other system physical parameters as Tp/Te and the external magnetic field strength. Moreover, a comparison between the first- and second-order rogue waves solution is presented. Our results show that the nonlinearity of the system increases by increasing the values of the non-Maxwellian parameters and the physical parameters of the system. This means that the system gains more energy by increasing r, q, Tp, and the external magnetic field through the cyclotron frequency ωci. Finally, our theoretical model displays the effect of the non-Maxwellian particles on the MI of the IAWs and RWs and its importance in D–F regions of Earth’s ionosphere through (H+,O2−) and (H+,H−) electronegative plasmas.

International audience; Orbiting Earth's dayside outer magnetosphere on 29 September 2015, the Magnetospheric Multiscale (MMS) satellites measured plasma composition, simultaneous electromagnetic ion cyclotron waves, and intermittent fast plasma flows consistent with ultralow frequency waves or convection. Such flows can accelerate typically unobservable low-energy plasma into a measurable energy range of spacecraft plasma instrumentation. We exploit the flow occurrence to ensure measurement of cold ion species alongside the hot particles—consisting of ionospheric heavy ions and solar wind He++—during a subinterval of wave emissions with spectral properties previously described as peculiar. Through application of the composition and multisatellite wave vector data to linear theory, we demonstrate the emissions are in fact consistent with theory, growing naturally in the He++ band with sufficient free energy.

Gyrotrons are high-frequency, high-power microwave sources with potential applications in plasma generation, energy generation, spectroscopy, and security. The Department of Science and Technology initiated the development of a 42 GHz, 200 kW, continuous wave (CW) gyrotron for the Indian Tokamak system through a multi-institutional project. The activity is targeted toward indigenous development of India’s first high-power gyrotron. In gyro-devices, frequency of operation is determined by the cyclotron frequency, and thereby the magnetic field. The development of a high-field intensity normal conducting cavity magnet was an imperative step during the testing and integration of the gyrotron tube assembly to achieve the desired beam transmission with a moderate operating cost. A high and spatially homogeneous magnetic field (1.61 T) is required to be established in the beam–wave interaction region by the cavity magnet. The desired magnetic field, as a function of axial distance from the gun to the collector, is governed by the requirements of gun optics, focusing field in the interaction region, and the adiabatic expansion of the beam into the collector. A water cooled electromagnet has been designed to produce the requisite magnetic field in the cavity region over an axial length of 40 mm with field homogeneity better than ±0.35%. Magnet design was optimized to meet the field requirements in the cavity and cathode gun. Magnetic field simulations were carried out in conjunction with the electrostatic field and space charge analysis. This paper presents finite element computations, design optimization, development and testing of a continuous duty iron core electromagnet for a first harmonic interaction mode (TE03) gyrotron cavity. Magnetic, electrical, thermal, and hydraulic design of the electromagnet is discussed in this paper.

Plasma current start-up and pre-ionization is an important motivation in Taban tokamak. The plasma current start-up has been successfully achieved using a central solenoid and a pre-ionization system and the experimental conditions have been optimized. Two distinct schemes were used to start-up the plasma current. Hot cathode emitter and electron cyclotron resonance (ECR) was used as the pre-ionization system. ECR pre-ionization circuit of 2.45 GHz magnetron was modified for long duration pulse mode. The transient plasma parameters were measured during discharge as a function of time in different conditions, while a toroidal field of 0.1 T with 4 ms flat-top was being applied. The experimental results showed that the plasma current could be started up by both ECR and hot cathode emitter. In the optimum conditions, a plasma current of 7.5 kA has been achieved with pulse duration of ~ 0.7 ms using the electron cyclotron pre-ionization system. Under such circumstances, the X-ray emission, as well as, the impurity level was minimized.

We developed an algorithm for processing of the dynamic spectra of plasma emission, which makes it possible to extract chirped elements with both increasing and decreasing frequencies. The algorithm was tested on a set of experimental data obtained by studying the emission spectra of the rarefied plasma of an electron cyclotron resonant discharge in an open magnetic trap. The efficiency of the method is close to 100% for signals with a signal-to-noise ratio of more than 30 dB and about 50% with a signal-to-noise ratio of 20 dB. This method can be used for automated analysis of dynamic emission spectra of both laboratory and space plasmas.