[en] Stark splitting of energy levels of a turbulent plasma is discussed. Experimental and theoretical data of stark splitting are reviewed. (U.K.)

[en] This paper presents a review of experiments in which different types of instabilities on relativistic electron beams have led to unprecedented levels of coherent electromagnetic radiation

[en] An experiment is underway to investigate the microwave and electron beam characteristics of a Free Electron Laser amplifier, similar to the Ubitron. In this experiment, a 35keV, 1A electron beam is produced by a thermionic cathode. The beam pulsewidth is 1-5μsec, with a 0.001 duty cycle. A guiding axial magnetic field, generated by a series of D.C. powered, water cooled solenoid coils, is variable up to a maximum of B/sub o/ = 3kG. This field both prevents radial expansion of the beam and allows investigation of the FEL gain near the resonance condition, k/sub o/V/sub ''/ - Ω/sub o//γ = 0. (k/sub o/ = 2π /iota, iota = wiggler period, Ω/sub o/ = (eB/sub o//m/sub o/), γ = (1 - β/sup 2/))/sup -1/2/). A set of 480 samarium cobalt permanent magnets produces a linearly polarized wiggler magnetic field. The wiggler is 60 periods long, with periodicity iota = 2.0cm, and entrance and exit tapers. The wiggler amplitude is variable from 0.1 to 1.0kG

[en] Observations are reported on a nonlinear, three wave interaction process occurring during high power electron cyclotron heating in the Versator II tokamak. The measured spectra and the threshold power are consistent with a model in which the incident power in the extraordinary mode of polarization decays at the upper-hybrid resonance layer into a lower-hybrid wave and an electron Bernstein wave

[en] Brief discussions of research progress are given for each of the following areas: (1) building equipment, (2) rf heating, (3) interferometry, (4) gas puffing, (5) mm collective scattering, (6) uv spectroscopy, (7) soft x radiation, (8) charge exchange, and (9) Thomson scattering

[en] The beam emittance and brightness from a mildly relativistic (200 to 400 kV) high current density (0.5 to 3.5kA/cm²) planar, field emission diode provided with a velvet covered cathode have been studied experimentally as a function of the applied electric field (100 to 600kV/cm). Transverse beam spreading has been measured using a conventional pinhole arrangement followed by a fluorescent screen and open shutter camera. Good turn-on, and a high normalized beam brightness (B/sub n/ = 300kA/cm²-rad²) have been observed. The results are compared with those obtained with a graphite cathode. 11 refs., 6 figs

[en] A survey is presented of tokamak devices and their role in magnetic fusion research. (U.K.)

[en] The research in plasma physics and controlled thermonuclear research at M.I.T. has evolved from a relatively long tradition of basic theoretical and experimental contributions, during the period covered by this contract. A major commitment to research in magnetically confined plasmas was undertaken with the Alcator program that began in 1969 and with the theoretical effort necessary to back this up. The Alcator A device was brought to successful operation and, after the identification of a sequence of plasma regimes that have been realized in it, let to attainment record values of plasma density, of the confinement parameter n tau, and of the degree of plasma purity. A second more advanced device, Alcator C, has been designed and is presently under construction. A line of toroidal experiments characterized by relatively low cost and extreme simplicity has been developed in order to study basic plasma physics problems related to magnetic confinement and relevant processes of plasma decontamination. The devices that have been operated are Versator I, now discontinued, Rector, with non-circular cross section, Erasmus, with small aspect ratio and Versator II. A number of theoretical contributions concerning the interpretation of the regimes found in Alcator, runaway phenomena, new trapped particle instabilities, internal resistive modes, etc. have been given and presented in publications or appropriate meetings. A special consideration, within the theoretical effort, has been devoted to the study of plasma regimes that are important in devising future experiments of thermonuclear interest

[en] A direct measurement of the extraordinary mode absorption at the second harmonic of the electron cyclotron frequency is reported. The experiments were performed in the ISX-B Tokamak. A transmitting antenna located on the high-field side of the ISX-B vacuum vessel launches a wave (ω/2π = 75GHz) along the direction of the major radius and in the equatorial plane of the torus. The wave is polarized in the extraordinary mode and is partially absorbed at the ω = 2ω/sub ce/ resonance layer. After passing through the plasma, the transmitted intensity is monitored by a receiving antenna located opposite, on the low-field side of the torus. In order to compare the measurements with theory, a correction had to be applied to thew data to compensate for refraction. A second measurement of the received signal is made at a different value of the magnetic field but maintaining the same density profile. The data is normalized to the received signal in this latter case where the ω=2ω/sub ce/ absorbing layer is not present in the plasma. Finally, a measurement of the extraordinary mode emission at the second harmonic of the electron cyclotron frequency was performed. As expected, when the absorption is strong, the corresponding emission at ω=2ω/sub ce/ is approximately at the blackbody level

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