A Ka- band gyrotron oscillator powered by a 600 kV pulse-line accelerator has produced approximately 100 MW at 35 GHz in a circular TE62 mode. It has also demonstrated frequency tuning over the range 28 to 49 GHz by operating in a family of TEm2 modes, with the azimuthal index m ranging from 4 to 10, by variation of the guide magnetic field. Operation is in general agreement with the predictions of theory.
The design of a 10-20-MW 40-ns cyclotron auto-resonance maser (CARM) is presented. The basic components of CARM are a pulseline accelerator, magnetic-field coils, a novel 600-kV 2 0 0 4 field-emission electron gun designed for p L / p z = 0.6 and A p z / p z < 3 percent, and a "whispering-gallery" mode rippled-wall cavity, designed for a high Q for the desired CARM mode and low Q for competing gyrotron modes. The NRL CARM operates with a wave group velocity that is less than optimum for autoresonance, but where the cyclotron maser instability is strong. By keeping the interaction region short (less than 10 cyclotron orbits), the effect of velocity spread is reduced, and the efficiency can be quite high; computer simulations indicate that the device will operate at efficiencies greater than 20 perstrength requirement is substantially reduced. The CARM can provide millimeter and submillimeter radiation in the first electi-on-cyclotron harmonic using currently available magnet technology. For example, the experiment at the is designed to produce powers in excess Of 10 MW at 100 GHz with a 600-kV beam and a magnetic field of only 25 kG, while a firstharmonic gyrotron at 100 G H~ with the Same beam voltage requires a magnetic field of over 70 kG.
FEL, the CARM can reach submillimeter wavelengthsResearch with a magnetostatic-wiggler cent.
A theoretical model is developed to describe the behavior of an ion-injection electrostatic confinement device. It is assumed that there is a shallow potential well in the center. Distribution functions, which are consistent with atomic processes occurring and with mechanisms leading to particle angular momentum, are obtained for ions and electrons. Using these distribution functions, Poisson's equation is solved to obtain potential and density profiles. By varying the experimental parameters, the conditions needed to go from a shallow potential well to a deep potential well are studied. The most important problems are found to be nonspherical focusing through grid construction asymmetry, and neutralization by electrons. Deeper wells are produced by increasing ion perveance, improving spherical symmetry, and reducing pressure.
An intense rotating relativistic electron beam of energy 500 kV and current 40−50 kA is injected into neutral gas of pressure 200−700 mTorr, in the presence of an external magnetic field B0≃800 G. It is observed that the ratio of the magnetic field on axis ΔBz(r=0) to B0 is ΔBz(r=0)/B0≃2.2. The average magnetic energy density is about 2.5×1016 eV cm−3. Spectroscopic results show that most of this energy is transferred to the plasma through Joule heating.
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