Experiments with a new type adiabatic crossed-field gun

In this paper experiments with a "long" crossed-field gun, designed by a method given by Kino, are described. This gun yielded the predicted value of current, but the other characteristics of the beam were not in accordance with the results of the theory. Experiments were carried out from which it may be concluded that there are RF instabilities present in the beam, instabilities which grow in the drift region and are generated at the cathode. The rate of growth of these instabilities is of the same order as the rate of growth of RF fields given by the theory of McFarlane and Hay.     

Some experiments with a new type of crossed-field gun

The construction and testing of a crossed-field gun based on an exact space-charge flow solution will be described. All the characteristic parameters of a gun of this type may be obtained analytically. Experimentally the gun was found to perform essentially as predicted. This gun has a moderately high convergence and produces a beam whose gross features give a very good approximation to planar Brillouin flow. Work by Anderson has indicated that crossed-field beams produced by a gun of this type may be somewhat less noisy than similar beams produced by other types of guns.     

A gun and focusing system for crossed-field traveling-wave tubes

A problem encountered in the design of crossed-field traveling-wave tubes (particularly M-type amplifiers or backward-wave oscillators) is a limitation on current due to the restricted cathode size in the usual gun systems. The scheme considered here incorporates into a crossed-field device the techniques commonly used in O-type devices for designing converging Pierce-type strip-beam guns, which can increase the effective cathode area by perhaps ten times. A design procedure is presented for getting a well-formed beam from such a gun, which is magnetically shielded, through a fringing crossed-field region into the uniform-field region of interaction. An analysis of electron flow through the fringing-field region, including the effect of space charge, is presented. A trajectory equation, solved on a digital computer, yields trajectories for the beam and design curves for various values of the important parameters. The results show the scheme to be feasible. Results are also presented from tests on an experimental, demountable tube used to test the focusing scheme. About 90 to 95 per cent of the current entering the crossed-field region could be focused to the collector, and the system behaved generally as the design predicted. An evaluation of the experimental data showed the scheme to be useful.     

A cathode-ray switch tube with 11 channels of electron multiplication

An 11-channel switch tube with 5 stages of electron multiplication has been developed. In some applications the switch tube will replace the camera-oscilloscope system for recording the rise times of electrical signals. This tube will be used to convert wide-band information from a single channel into eleven channels of lower bandwidth information which can be transmitted over standard telephone cables for telemetering operations. Venetian-blind dynodes are used for the multiplier structure. Each channel is defined by a pair of louvers on the dynode disk. U-shaped shields, which just straddle the louver edge of the preceding dynode, are used to minimize crosstalk. The channel width is 0.120 inch or a total length of 1.32 in for the 11 channels. The collector system provides a method for equalizing the gain of all the channels. The switch tube is 3 in in diameter and 24 in in length. Operating at a 4-kv beam potential with 2-µa beam current, the tube provides 20 ma of output current, with less than 5 per cent crosstalk to adjacent channels. The electron optics and the performance of the tube are described.     

The experimental characteristics of a wide dynamic range crossed-field gun

This paper briefly describes the experimental verification of the properties of a wide dynamic range crossed-field gun [1]. This gun, which is a combination of a Kino short gun (or it could be a Kino long gun) and a two-section transformer region, can be used to inject electron beams (with cathode current density varying over a wide range) into the interaction region under optimum conditions and under conditions of a fixed magnetic field. The beam injection level and its injection velocity can also be varied over a wide range by suitably adjusting the electric fields in the two sections of the transformer. The fabrication of the experimental tube is also briefly described.     

A high-sensibility cathode-ray tube for millimicrosecond transients

A high-sensibility cathode-ray tube has been developed for the photographic recording of transients in the millimicrosecond region. The new cathode-ray tube uses a traveling-wave deflection system with magnetic focusing and attains a spot diameter of 0.001 inch. The first models have a sensibility of 0.026 volt/trace width and a writing speed of 10¹¹trace widths/second. Improved production models are expected to have sensibilities of less than 0.02 volt/trace width. In this particular application, sensibility in volts per trace width and writing speed in trace widths per second are the significant performance characteristics. Analysis of the dependency of these on several important parameters in the general cathode-ray tube design shows that the use of a much smaller spot and display than is conventional results in large gains in sensibility. Analysis also indicates that maximum sensibility is achieved with the deflection plates located in the lens region. Magnetic focusing is used to permit this optimum deflection plate location. To allow the choice of long plates with short effective transit time, a traveling-wave deflection system is employed. Postdeflection acceleration is introduced to obtain high writing speeds.     

The electron beam in a cathode-ray tube

The beam in a cathode-ray tube is described by a "paraxial" Liouville equation. This equation takes into account the thermal spread of the electrons as well as the influence of the space charge of the beam. The solution of this equation is given. An ordinary differential equation is derived for the beam radius. The equation has been solved in the field-free region outside the gun. The result is presented in graphs which can be applied to the determination of the spot size on the screen of a cathode-ray tube.     

A high luminance high-resolution cathode-ray tube for special purposes

For those applications where light sources of high radiance or displays of high resolution are necessary, miniature cathode-ray tubes have been developed with monocrystalline luminescent screens. These newly developed screens consist of cerium-doped yttrium-aluminum garnet (YAG), epitaxially grown on commercially available YAG substrates; they have an excellent heat conductivity and are optically clear. The construction of the tube and its performance in two modes of operation are described. When the tube is operated with a continuous undeflected beam, the luminance of the spot is limited by thermal quenching of the phosphor material. Under these circumstances, the maximum luminance of 1.9 × 10⁸cd/m²(0.55 × 10⁸FTL or 4 × 10⁵W/m²sr) is reached at a power of 70 mW in a 3.5-µA 20-kV beam, focussed to a spot of 9 µm diameter. Equipped with appropriate deflection coils and scanned with an interlaced field of 575 active lines and 25-Hz repetition frequency, the tube can handle up to 20 W of beam power in a 12 × 16 mm²image area. In this mode, the luminance is limited by the design of the electron gun and the desired resolution. At 20 kV and 100 µA (i.e., at 7500 cd/m²) the tube has a half-intensity linewidth of 60 µm, which is equivalent to 500-TV limiting response lines in the same 12 × 16 mm²area.     

The DEMATRON—A new crossed-field amplifier

A nonreentrant beam, distributed-emission, crossed-field, forward-wave amplifier, the DEMATRON, is described. The difficulties encountered by early experimenters in achieving gain in excess of 6 db in nonreentrant, crossed-field amplifiers are overcome in the DEMATRON by use of either an electron velocity taper or circuit velocity taper. A crossed-field amplifier design theory is given which is based on the use of equivalent magnetrons, and which takes into account the need for velocity compensation. In practice, electron velocity compensation is accomplished by either changing the sole-anode spacing, or by varying the dc magnetic field or a combination of both. Experiments with the DEMATRON have yielded gains in excess of 10 db over a 15 per cent bandwidth. Power levels between 300 and 500 kw have been achieved at an operating voltage of 25 kv. The design theory has been experimentally shown to be quite satisfactory in the large-signal, saturated gain region of operation, However, the lack of adequate small-signal theory has thus far prevented full optimization of the velocity compensation.     

The cycloidotron, a proposed crossed-field, fast wave millimeter tube

In general, the electrons of an electron beam in crossed electric and magnetic fields move in cycloids. The possibility of using such a beam in harmonic operation of a periodic-beam fast-wave tube has been explored. The most promising tube of tiffs type for a millimeter generator is one in which the ac motion occurs along the dc magnetic field and consequently is transverse to the dc motion. The small signal analysis of this tube is given, neglecting space charge, and it is shown that for reasonable beam currents backward wave oscillations at twice or even three times the cyclotron frequency can be obtained. The analysis is made particularly simple through the use of the small signal power theorem. Some of the practical problems associated with this tube are briefly considered.     

Direct synthesis of crossed-field electron guns—A novel gun for producing Brillouin flow

A direct approach to the synthesis of crossed-field electron guns is presented. An iterative approximation to the desired beam form is achieved by application of the paraxial ray equation alternatively solving for potential and curvature along the beam while maintaining certain end-point conditions and the desired convergence pattern. When sufficient accuracy is obtained, polynomial approximations are used to express shapes of the trajectories and the electric fields along the beam edges in analytic form. The electrodes to produce the necessary electric fields along the beam edges are calculated by Kirstein's method. A conformal transformation is used to transform the beam edge into the real axis of a complex plane and analytic continuation of a suitable complex potential function is employed to find equipotential lines. These are transformed back into the plane of real coordinates and are surfaces along which electrodes can be placed. A novel short gun which produces a Brillouin beam has been designed using the iterative approach. The availability of beam curvature as a variable has made it possible to find an electrode system which controls the transition from the cathode-region flow characteristics used in Kino's short gun to a drift Brillouin beam. Detailed experimental evaluation of the gun reveals that the beam characteristics are in good agreement with those predicted theoretically.     

Low-voltage color tube gun assembly with periodic focusing

One type of color tube, often referred to as the post acceleration color tube, requires a gun of unique design. The gun operates at relatively low voltages of 5000 to 7000 volts as compared with 20,000 to 30,000 volts in other types of color tubes. The tricolor gun assembly described consists of three individual guns arranged in a plane. This limits the inside diameter of the electrodes to 0.358 inch as compared with half an inch or more in conventional guns. The individual guns are either triodes or tetrodes with periodic focusing. In spite of the above mentioned restrictions the spot size is about 0.038 inch at 300 microamperes screen current per gun and 7000 volts anode voltage. The depth of focus is very satisfactory because of small beam diameter.     

A nonreentrant crossed-field amplifier with cycloiding injected beam

Nonreentrant injected-beam crossed-field amplifiers usually employ a thin laminar beam positioned well above the sole electrode. In operation, the beam is gradually bunched by a phase-focusing action. This paper describes the analysis and demonstration of such an amplifier, with an important difference: the electrons of the beam have random cycloidal trajectories extending to the sole instead of following the usual linear paths, Rapid and effective bunching is accomplished by collecting antiphase electrons on the sole. Experimental results are presented to show that the approach is useful for high current beams. For example, an output power of 600 watts was obtained at 10 dB gain from an 800 mA beam. The advantages and disadvantages of the cycloidal motion are discussed. The results of computations are given to show the desirable characteristics attainable; for example, a design for an amplifier with a cycloiding beam requires only 35 percent of the interaction length of a laminar-beam type for the same computed power output, gain and efficiency at the same cathode voltage.     

Evaluation of the DC parameters and noise transport in the gun region of an injected-beam crossed-field diode

A half-Maxwelliany-component velocity distribution and a full-Maxwellianz-component velocity distribution are assumed in order to evaluate the position and depth, ymand Vm, of the potential minimum as a boundary-value problem. The various dc parameters such as the voltage distribution, space-charge density, velocity and current density components and trajectories are then evaluated as an initial-value problem. The results obtained in this manner agree closely with the results obtained from the Kino gun model except that they-component current density is not constant, as is usually assumed in the Kino gun model. The steady-state parameters are calculated here for both temperature-limited and space-charge-llmited conditions. The Kino gun results are shown to be essentially those for space-charge-limited operation. Even though the injection conditions under the two types of operation are identical, the formation of a potential minimum considerably changes the electron trajectories and the corresponding velocity components. The growth rate of a hybrid wave is reduced as ωpis decreased and/oromega/omega_{c}is increased, and the propagation constants of the two conventional space-charge waves are modified, the over-all growth rate of the slow wave being greater than that of the fast wave. For large values of ωpthe conventional fast space-charge wave is a backward wave, although it becomes a forward wave ifomega/omega_{c}is large. It is noticed that the conditions in the gun region are more favorable to the existence of low-frequency perturbations. Based upon these results several experimental observations made at various laboratories are explained qualitatively.     

A new electron gun for picture display with low drive signals

The paper discribes an approach to the problem of picture tube guns for small signal service. A Pierce-type cathode delivers a collimated parallel beam of 1600 microamperes at 250 volts (microperveance: 0.4). This beam is injected into a cylindrical cavity of appreciable length (3/4-inch long, 1/4-inch diameter). It is focused upon a small aperture at the far end using a parabolic axis potential. This axial focusing field is approximated by three cylinder segments at two intermediate voltages. To modulate the beam by lateral deflection, the cavity is again bisected through an axial plane and signal voltage is set up between half cylinders. This modulation by two crossed-electrostatic fields ("CFM" modulation) has been successfully applied in transistorized television, using a seven-volt video signal on a beam of 900 microamperes.     

W波段回旋行波管新型曲线阴极磁控注入电子枪优化设计

设计了采用新型曲线阴极结构的W波段双阳极磁控注入电子枪,手动优化得到的电子注参数在速度比1.1时,纵向速度零散为1.84%.为了克服手动优化方法的繁琐和低效,引入了数值计算方法的优化策略,编制了基于MATLAB语言的遗传算法和模拟退火算法的优化程序,并结合二维电子光学软件EGUN对该W波段曲线阴极结构电子枪进行优化,优化得到的电子枪在保证电子注速度比1.1的情况下,纵向速度零散分别达到了0.81%和1.05%.与手动优化方法相比,数值优化方法不需要设计者干预优化过程,具有自动高效的特点,且优化结果更好.     

A large-signal analysis of beam-type crossed-field traveling-wave tubes

The equations describing a two-dimensional model of a beam-type crossed-field device are presented in a form adaptable to numerical computations. A method of computing the space-charge forces similar to that used by Tien, Walker, and Wolontis in describing the ordinary traveling-wave tube is outlined and the difficulties associated with this method are pointed out. Numerical results covering the interaction of a thin beam with a backward or a forward wave are presented for a variety of space-charge conditions. Space-charge effects reduce the large-signal gain of a backward-wave amplifier; it appears that 70 per cent conversion of available potential energy to RF energy would be excellent efficiency. Space-charge fields appear to have little influence on forward-wave interaction. For either forward- or backward-wave interaction, the computations indicate that a large fraction of the beam current is collected on a very short length of circuit, thus placing a limitation on the average power capabilities of such a crossed-field device.     

Analysis of a new crossed-field amplifier, the "EAL," or electromagnetic amplifying lens

A new form of crossed-field microwave and millimeter wave amplifier which combines an interaction process that results in axial gain with a quasi-optical handling of the RF input and output power is described. Because of its functional similarity to a microwave lens and the additional property of amplification, it is called the Electromagnetic Amplifying Lens. Its advantages are outlined, and its interaction mechanism considered in detail. It is shown that the voltage gain is a linear function of distance in the useful operating range. When the RF level is low, interference between forward- and backward-traveling waves on the waveguide results in loss of control of the space charge. This phenomenon limits the gain available with stable device operation; useful gain of at least 20 db is theoretically possible with a bandwidth of several per cent. The crossed-field interaction principle that is employed assures efficiencies of better than 50 per cent.     

The nonlinear operation of a microwave crossed-field amplifier

A nonlinear, three-dimensional, partial differential equation modeling the operation of a microwave crossed-field amplifier is discussed and analyzed where the nonlinearity is considered weak. Amplification mechanism, amplification range, and phase characteristics are discussed. Predicted results are compared with experimental data.