Azimuthally periodic electrostatically focused electron ribbon beams

Methods of enhancing transmission of ribbon-shaped electron beams undergoing circular motion in azimuthally periodic cylindrical electrostatic lenses are treated. Lens forces add to the naturally occurring curvature focusing to achieve this increase in beam transmission. Three basic configurations, differing only in the method of applying lens voltages, are treated: symmetrical focusing, deflection focusing, and asymmetric focusing (including inner and outer electrode segmentation). Expressions for beam perveance and rippling are derived from the paraxial-ray equation for thin electron ribbons advancing along a two-dimensional curved optical axis. The stiffness of azimuthally periodic electrostatically focused electron ribbons (i.e., the immunity of the beam to transverse disturbing forces) also receives attention. Mathematical extensions of the analysis to ribbon beams undergoing helical motion are discussed, and numerical results applicable to selected values of lens parameters are presented. Experimental results for an azimuthally periodic lens, constructed to test the analysis, are discussed in light of the theory developed.     

Measurement of noise along electrostatically focused electron beams

Noise along periodic-electrostatically focused electron beams have been measured. The noise variation is periodic with the wavelength of the reduced plasma frequency. It is concluded that electrostatic focusing exhibits similar noise properties as magnetic focusing.     

Influence of velocity spread on gain and efficiency of klystrons

This paper presents the calculation of the effect of velocity spread in electron streams on the gain and efficiency in klystrons. Using the density-function method and assuming a half-Maxwellian velocity distribution, a small-signal theory of a klystron tube was developed. The form of the solution is a power series whose coefficients contain even powers of ω q/ω. The effect of losses in the cavity has also been included. The results are presented as plots of the ratios of the ac component of the bunched current with velocity spread vs a dimensionless parameter that is a measure of the velocity spread. The plots contain ωq/ω, the lengths of the drift tube and of the gaps as important design parameters.     

Small-signal gain measurements and vibrational distribution in CO

Small-signal gain measurements on a large number of vibrational-rotational lines in a CO-laser plasma have led to the vibrational distribution from theupsilon = 2toupsilon = 31level. The relative influence of V-V and V-T relaxation processes is discussed.     

Efficiency calculations of resonant coupled cavity output section of broadband klystrons

The efficiency of the output section of broadband klystron with resonant copled cavity is calculated. In the solution of that problem, neither the time integrated electron disk model nor the space charge wave theory is used. The disk model requires too long computer time, and the space charge wave theory is rather simplistic. A new modified method is proposed, with which the computer time is saved much more and the calculated result is in fair coincidence with the measured one.     

Nonlinear mixer gain calculations for Josephson junctions

We have numerically solved the steady-state solutions of the initial value problem associated with a current-driven Josephson weak-link junction shunted by an ohmic resistance. The nonlinear mixing action of the junction leads to Shapiro steps in the DC response with step height in units of the mixing frequency. Mixer gains have been calculated with a wide range of parameter values and intrinsic chaos is observed whenever Shapiro steps are prevalent     

Small-signal gain performance of the permeable base transistor at EHF

The small-signal amplifier performance at 40.5 GHz is reported for a GaAs permeable base transistor (PBT) having a base grating of 3200-Å periodicity and 1-mm periphery. The device was embedded in a microstrip circuit with appropriate matching networks and biased for optimal small-signal gain with Vbe= 0.2 V, Vce= 2.0 V, and Ice= 59 mA. The prototype amplifier achieved 11 dB of stable gain at 40.5 GHz. The circuit design was facilitated by the moderate impedance levels and highly unilateral nature of the PBT.     

A UHF traveling-wave amplifier tube employing an electrostatically focused hollow beam

The increasing importance of beam-type microwave devices has stimulated interest in focusing methods other than the usual uniform magnetic field. One such method applicable to hollow cylindrical beams, proposed by L. A. Harris, utilizes a radial electric field acting on a spinning beam to counterbalance the space-charge divergence forces. A traveling-wave amplifier operating in the 300 to 600 mc region, employing this focusing method, was designed and constructed. Experimental results obtained with this tube are presented. Beam transmissions as high as 90 per cent and net gain over 15 db were obtained. Practical considerations and tube design factors are discussed. The primary advantage of this kind of focusing is in the elimination of the solenoid, and consequent reduction in power supply requirements and weight, accessibility of rf connections to the tube, and elimination of capsule and aligning adjustments. This focusing method appears to have great potential usefulness in hollow-beam applications, and particularly in devices where the spiral motion of the beam can be made to interact with a spirally traveling wave.     

连续波化学氧碘激光器的小信号增益和腔内损耗

本文用变耦合率方法和平行板转动最大损耗法分别测出小信号增益为1.60×10~(-3)cm~(-1)和1.75×10~(-3)cm~(-1),腔内损耗为12.0％,获得了饱和参量为3.00kw/cm~2,并将所得结果与其它报道作了比较。     

Small-signal gain and saturation parameter of a transverse-flow CW oxygen-iodine laser

The small-signal gain and saturation parameter of a transverse-flow CW oxygen-iodine laser have been experimentally obtained for the first time from output power measurements made as a function of the cavity losses without using a CW probe laser. These measurements typically yieldalpha_{0} simeq 0.045m^-1andI_{s} simeq 0.44kW/cm²for a Cl2flow rate of1.4 times 10^{-3}mol/s with an I2flow rate of4 times 10^{-6}mol/s. The dependences of the small-signal gain and saturation parameter have been also found on the Cl2flow rate. These behaviors are qualitatively explained by a simple two-level model.     

Design and performance of an electrostatically focused 5-kw X-band traveling-wave tube

A new type of high-power traveling-wave tube employing electrostatic beam focusing was developed and tested. An electrode system permitting the electrostatic focusing of a high-perveance electron beam was evolved and the incorporation of the focusing electrodes in the slow-wave circuit was accomplished without significant deterioration of the original RF characteristic. Feasibility was proven on a narrow-bandX-band amplifier operated in a continuously pumped vacuum chamber which produced up to 10 kw of peak power. A sealed-off wide-band tube, subsequently, gave 2.5 kw over a 26 per cent bandwidth.     

Small-signal analysis of wavelength conversion in semiconductorlaser amplifiers via gain saturation

Wavelength conversion due to gain saturation in a travelling wave semiconductor laser amplifier is analyzed using a small-signal model. An analytic expression is developed showing that the small-signal bandwidth of wavelength conversion is not limited simply to the carrier modulation bandwidth, but also depends on the single-pass gain of the device     

Multiple extraction cavities for high-power klystrons

The design and performance of an X-band high-power klystron amplifier utilizing an output circuit consisting of two uncoupled output cavities are described and compared with 2-D computer simulation results. It is shown that good efficiency, low RF gap gradient, relatively uniform power extraction from each cavity, and freedom from oscillations due to extraneous modes can be achieved. The change in phase relative to the RF input for the two extraction cavities is relatively small within a frequency bandwidth on the order of 1%, when the beam voltage or drive power is varied over a moderate range. For narrowband applications, where the combining of the separate outputs is desired, good combining efficiency is possible. The number of extraction cavities can be extended to obtain still higher peak powers     

Design considerations for submillimeter-wave reflex klystrons

The problems facing the development of klystrons for use at submillimeter wavelengths are reviewed. Analytical formulas for reentrant cavity resonance, starting conditions, output power, and oscillation buildup are presented. This paper describes methods of calculating cavity Q-factor, output coupling, focusing potentials, electron paths, and heating effects. The scaling of output power with frequency is derived. Examples of techniques that might be used to realize a working device are presented.     

On primary incident wave models for pyramidal horn gain calculations

A few widely used primary incident wave models for pyramidal horn antenna analysis are compared on the basis of gain calculations. The analysis is based on edge-wave diffraction theory, as presented in a previous publication, with some modifications made to the underlying theory. It is shown that these models agree well for high-gain horns with small flare angles, but that the differences are more profound for lower gain horns, where the flare angles are larger. The accuracy of the various models are studied by comparing the results to actual measurements. The respective effects of amplitude and phase variation in the primary incident wave are also illustrated.     

High-power klystrons for the Next Linear Collider

The Stanford Linear Accelerator Center (SLAC) version of the 1 TeV next linear collider (NLC) requires a 4:1 increase in drive frequency, from the 2.85 GHz of the 1 TeV Stanford Linear Collider (SLC) to 11:4 GHz for the NLC. More than eight years have gone into the development of a new 75-MW klystron for powering the NLC. The increase in power density and surface RF gradient at the higher frequency have rendered previous RF window and circuit designs unusable. Following numerous catastrophic gun, cavity, and window failures, new designs have evolved that solved the problems. As history's most ambitious klystron development enters its last year, the result includes a robust 75-MW peak power solenoid-focused, 50% efficient klystron. Not far behind is a 60-75-MW periodic permanent magnet (PPM)-focused 60% efficient version that will reduce the NLC electric power bill by tens of millions of dollars per year     

An efficient and accurate method for gain spectrum calculations innon-identical multi-quantum-wells

This paper describes a semi-analytical approach, with no discretization, for gain spectrum calculations in multi-quantum-well structures, based on the Galerkin method. After a brief presentation of the physical model and development of our method, we show with some examples that this method is superior to the discretized finite-element method in terms of computation time