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A phase-space distribution of a weak electron-beam injected into a cold plasma is experimentally investigated in electron time scales. It is shown that electron-beam holes in phase-space evolve dynamically from appearance to collapse, as synchronized with a wave packet dominated by a beam mode. The dependence of the hole velocity radii on the packet crest amplitudes indicates that the holes are induced by self-trapping of the beam. It is found that the beam is well trapped while the packet grows linearly, but easy to be detrapped after that.

It is observed that electron-beam holes in phase-space evolve dynamically from arising to collapsing in electron time scales in an electron-beam-plasma system. The holes are synchronized with a wave packet dominated by a beam mode of the two-stream instability, and their velocity radii depend on the amplitudes of the packet crests. This shows that the holes are induced by the self-trapping of the beam. The observed images indicate that the holes keep alive due to the hard detrapping of the beam during the packet linear growth, but begin to collapse due to the easy detrapping in the packet saturation.

We have observed repetitive, large-amplitude (> 80 kV/cm) parallel electric-field wave packets with electron density modulation in the current limiting phase of a high-voltage linear plasma discharge. The power spectral density of the whole span of the wave packets shows the peak frequency, 65 MHz, in the vicinity of the lower hybrid frequency.

Spatial cyclotron resonance of an ion beam in a wavy magnetic field is investigated to realize the separation of stable isotopes. To perform the experiment, a surface-ionizing lithium ion beam source, which is collisionless and charge-neutralized, has been developed. A wavy magnetic field is produced by setting two magnet-arrays face to face. At the resonance condition, clear scattering of the lithium ion beam is observed and the concentration of 6 Li is obtained on a target.

Two categories of electron energization associated with a strong Buneman double layer are discovered by the simultaneous observation of both the directivity of hard X-ray (bremsstrahlung) fluxes and the plasma diamagnetism. One is characterized by production of nonthermal electrons with a highly anisotropic velocity distribution, and the other by production of a hot electron plasma, almost thermal in the bulky sense.

The behavior of lithium ion beams in a periodic wavy magnetic field is investigated experimentally to prove the spatial cyclotron resonance of selected isotope. Surface-ionized lithium ion beam source, which is collisionless and charge-neutralized, has been developed to perform the experiment. The wavy magnetic field is produced by setting arrays of magnets face to face in a homogeneous magnetic field. The spatial cyclotron resonance is clearly observed at the resonance condition. This resonance can be used to perform the lithium mass separation.

One dimensional nonlinear evolution and localized structure of a high frequency beam mode were experimentally studied. Test waves were first linearly unstable, but stabilized in the nonlinear stage. The wave envelope behaved such as ki sech [ki(z-zo)] as a function of position z along the beam path, where ki is the linear growth rate. The results are discussed by a nonlinear theory on unstable beam waves in an electron beam plasma.

An ion energy increment by externally excited ion acoustic waves has been studied in a simple double plasma device. The energy increment was measurd in detail by means of a small electrostatic energy analyzer whose resolving power was better than 0.1 eV. A small energy increment of about 10% was observed under the condition where ion fluctuations caused by the wave fields were less than 10% and the ratio of the electron-to-ion temperature was about 10. The measured energy increment was approximately proportional to the wave frequency and to the square of the wave potential. The fact is well understood if the wave energy is transferred to the ions through the Landau damping. The electron energy increment, however, was negligible in accordance with the above interpretation.

Using a coaxial double-plasma device of a new type, we excited lower hybrid waves propagating almost perpendicularly to the magnetic field. The dispersion relation of the excited waves agree well with the theoretical value obtained with the warm plasma approximation. These waves were mainly subject to the ion Landau damping, and then the ion energy efficiently increased in the direction perpendicular to the magnetic field.

Plasma density distribution and low frequency noise spectrum have been measured in detail around a line cusp field generated by permanent magnet arrays in Ar, Ne and He plasmas. Low frequency broad noise spectrum with a fairly sharp peak or peaks, respectively, 10, 15 and 30 kHz were observed in those plasmas. The frequencies of these peaks are consistent with an interpretation in terms of a low frequency drift wave instability of the universal type, with k ·B = kB . Another possible explanation in terms of an ion-cyclotron wave is discussed.

The propagation of an ion-acoustic soliton in an Ar (or Ar–He) plasma is investigated experimentally in a double plasma device. The various patterns of signals propagating from the separation grid into the target region are classified into three types, Besides the normal soliton pattern, there appear signals with either a shallow dip or a deep valley. The K–dV equation with a term expressing the effect of ion Landau damping is solved numerically with parameters corresponding to the experimental conditions. One of the types observed in the experiment (with a shallow dip) is fully reproduced theoretically with the corresponding plasma parameters. Effects of the initial height of the perturbation on the evolution of the signal are investigated experimentally and theoretically. The minority He ion which causes an increase of the ion Landau damping rate had the same effect as the decrease of the initial height of the signal.

Parametric excitations of ion plasma oscillations are investigated by using a simple model based on the modulation of ion density in the uniform electron background. This model is useful to calculate the higher order nonlinear terms, and gives a good interpretation to the new nonlinear phenomena observed in a mercury vapour plasma without magnetic field. The nonlinear effects observed are; (1) the frequency shift and the amplitude increase of the resonant oscillations with increasing of pumping power, (2) the existence of the resonance frequency region, and (3) the asymmetrical parametric excitation with hysteresis.

Nonlinear phenomena in parametric resonances of electron plasma oscillations predicted and partially found out in previous papers (J. Phys. Soc. Japan 30 (1971) 309 and Rep. Fac. Sci. Shizuoka Univ. 5 (1970) 9) are investigated. A frequency of externally applied electric field f ex swept automatically near twice the plasma frequency 2 f pe and an amplitude of oscillations excited with resonance frequency f r ≃ f pe are displayed on the X - and Y -axes of a monitor scope, respectively. Threshold values of pumping voltage V 0 for the parametric excitation of the oscillation and nonlinear shift of the resonance frequency due to the input voltage V in were measured, and the asymmetrical hysteresis curve of the excited oscillation amplitude for increasing and decreasing f ex was easily observed by convenient method in which the detection frequency f r was swept by a servomotor. Parameters including a collision frequency and an electron density gradient are also determined from experimental data.

Using a coaxial double plasma device we excited the lower hybrid wave in an argon plasma in mirror magnetic fields. When the lower hybrid wave was excited the perpendicular ion energy E⊥ and the plasma density n were increased. A relation between the relative changes of the average energy ΔE ⊥/ E ⊥ and the density Δn n agrees very well with a relation expected from loss-cone considerations.

Plasma density increment is calculated when the ion energy is increased transversely in a magnetic mirror in stationary scheme. Increase in the transverse energy of ions decreases number of ions with velocities in the loss cone. Electron density is assumed to be equal to ion density. It is found that the relative change of the plasma density is proportional to the relative change of the transverse ion energy and the coefficient of the proportionality is given.

An ion heating by excited lower hybrid waves has been observed in a coaxial type double plasma device. The lower hybrid resonance heating is examined on the two components of the kinetic energy perpendicular and parallel to the magnetic field.

Mesure des distributions du potentiel spatial, des courants de saturation des ions et des electrons du plasma d'argon autour de deux sortes d'obstacles immerges dans un ecoulement de plasma supersonique, de nombre de Mach 3 a 5. Des lames metalliques (acier inoxydable d'epaisseur 0,3 mm) et des lames de verre (d'epaisseur 3 mm) ont ete utilisees comme obstacles

Lower hybrid waves were excited in a coaxial type double plasma device, where their wave vectors were almost perpendicular to the magnetic field. The dispersion relation of the excited waves agrees fairly well with the theoretical one. The waves are effectively excited by the sinusoidal potential differences between the driver and target plasmas without insertion of metal electrodes. The method may be applicable to the plasma heating due to lower hybrid waves in high temperature plasmas.

Asymmetrical and hysteresis behavior on a parametric excitation of ion plasma waves was observed in a mercury discharge plasma with no magnetic field.