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The purpose of this work is to study the theoretical effects of avalanche multiplication and collector transit time on microwave controlled avalanche transit-time triode (CATT) devices. The objectives of this report are to obtain a better device model, develop a complete one-dimensional large-signal simulation computer program, calculate the large-signal performance of Class C CATT amplifiers and make a comparison between Class C CATT and Class C BJT amplifiers.

The purpose of this program was to carry out fundamental studies in semiconductor materials and devices which are suitable for improving the state of the art in microwave and millimeter-wave power generation, amplification and detection. During the past year there were several active tasks under this program. A summary of each task is included in this report.

Several different IMPATT diode structures operating in the precollection mode at X-band (9 to 11 GHz) are examined, both using a complete finite-difference program and a simplified analysis which is developed in the report. The details of the precollection mode are examined, and large-signal solutions are presented for each different structure. Both single- and double- drift diodes are considered. Dynamic temperature effects are included and the differences between simulations at constant temperature and those with variable temperature are noted.

The objectives of this investigation include the development of a large-signal characterization procedure for nonlinear active two-port networks, analysis of the large-signal properties of MESFETs, and establishment of a large-signal MESFET equivalent circuit model. An approach for characterizing the single-frequency properties of a nonlinear two-port network is presented. The characterization results are useful in optimizing the external circuits for particular applications such as amplifiers and oscillators. The information obtained regarding network properties can be used for establishing amplifier and oscillator design and stability criteria. A GaAs MESFET was used as the nonlinear active two-port network, and its large-signal characteristics were measured. The nonlinear properties of the MESFET were investigated over the 7- to 13 GHz frequency range. The common drain configuration was studied extensively since this configuration is particularly advantageous for oscillator applications., Report on Millimeter-Wave Circuit Analysis and Synthesis.

The results of an experimental investigation into a new approach to circuit-level power combining of negative-resistance devices are presented. The approach uses the properties of symmetric lossless TEM line combining networks together with the bandlimited characteristics of IMPATT diodes to achieve stable combiner designs having improved bandwidths over other approaches. The combining networks utilized in this investigation fall into the category of N-way nonresonant combiners which are often associated with various bandlimiting resistive stabilization techniques for suppressing non-power-producing interactions among the devices. This combining design requires no such stabilizing scheme. Suppression of undesired odd modes is accomplished in lossless circuits by an appropriate combinations of device and circuit which provides the necessary condition for a stable combiner.

A model of millimeter-wave Si IMPATTs has been developed which includes transient transport effects neglected in the conventional drift-diffusion model. The new model is based on principles of energy and momentum conservation. The model uses the first three velocity moments of the phase-space transport equation. Terms accounting for the effects of collisions incorporate energy dependent relaxation times and ionization rates.

Theoretical investigations of IMPATT diodes are carried out at 30, 40, 60 and 94 GHz. GaAs, Si and InP diodes are simulated. Several single- and double-drift doping profiles are considered. Extensive results as a function of RF voltage amplitude and dc current density are presented. Taking thermal resistance into account, the expected CW performance of each structure is presented, such that the maximum allowable diode temperature is 525 deg K. Matching each device to 1-ohm circuit resistance gives an estimate of maximum obtainable pulsed power. Finally, CW and pulsed performance for all structures and materials are compared over the entire frequency range simulated. (Author)

A steady-state liquid phase epitaxial growth system is being used to study the factors that influence the nucleation, growth and purity of InP. Humidity (>30% relative) has been found to be a major contaminant that leads to erratic growth morphologies and poor electrical properties. With the growth system and substrate preparations in a low humidity (<20% relative) room the reproducibility of epitaxial growths has been improved. The discoloration of the bone white pyrolytic boron nitride growth cell has helped to identify several sources of contamination that oxidize the In-melt and lead to premature nucleation. The nucleation and growth of epitaxial InP now appears to be limited by phosphorus transport instabilities in the P-saturated In-melt. A thermochemical analysis of phosphorus equilibria with In and InP may provide an insight into liquid solid stability conditions. The results are in excellent agreement with the stability of the In-P liquidus curve and InP substrates under PH3-H2 mixtures. The analysis appears to indicate that the partial pressure of P4 controls the nucleation of InP and the stability of the In-P liquidus curve. At temperatures below 700 deg C the partial pressure of P2 is greater than that for P4 and appears to stabilize the InP substrate degradation. (Author)

A method for simulating the dynamic behavior of pulsed IMPATT oscillators using a quasi-static approximation is presented. The method used to characterize the IMPATT diode is explained. A particular circuit model is used which models the cylindrical cavity power combining circuit. The overall device-circuit interaction technique is outlined. Simulation results for a high-low, single-drift X-band GaAs IMPATT are presented. The method presented here can be employed for any type of IMPATT device. The pulsed oscillator properties of double-drift IMPATT diode structures are presently being investigated. (Author)

This technical report contains a description of a quasi-two-dimensional model for GaAs FET operation. The model is based on modified expressions for the carrier continuity and Poisson equations in the conducting channel of an FET. The model is compared to full two-dimensional results to determine its accuracy. It is then used to study a variety of operating conditions. The effect of various material and device parameters are also discussed. (Author)

Circuit design and stability criteria are developed for a new class of IMPATT diode power combiners. These combiners make use of radial-symmetric circuits and provide an optimal integration of device and circuit properties to perform the power adding function. Both lossless N-way combiners and resistively stabilized N-way combiners are considered. Examples of this combining technique are given at frequencies of 10 GHz and 90 GHz which make use of realistic IMPATT diode parameters. The 30-W, ten-diode lossless X-band combiner indicates a 1-dB locking bandwidth of 300 MHz and 10 dB gain, while the millimeter-wave combiner provides a 1-dB bandwidth of 9 GHz at 87 GHz and 10 dB locking gain. A 100-W, resistively stabilized 10 GHz, ten-diode combiner shows a 150 MHz locking bandwidth, also at 10 dB locking gain. (Author)

Liquid phase epitaxial layers of InP have been grown at 475 degrees C by a steady-state growth technique that maintains the substrate at a constant temperature. The growth system has excellent temperature control, fast thermal response, uniform temperature profiles and up to 50 degrees of C/cm temperature gradients can be induced normal to the substrate. To achieve uniform nucleation on InP substrates at these low temperatures a submersed-displacement cleaning procedure was developed that uses a dilute HCl-methanol etch to remove oxides. The initial layers were discontinuous and had poor electrical properties due to oxide contamination in the In-melt and to substrate oxidation during the heat-up cycle. New in and the covering of the substrate with InP during heat-up appears to have solved this problem. Thermodynamic models of the growth system indicate that the graphite growth cell increases the decomposition of fused quartz and introduces C, O and Si into the In-melt. (Author)

The properties of BARITT devices and their application as mixers and detectors particularly at millimeter wavelengths have been considered and their characteristics have been determined. It is shown that the BARITT device will have several advantages over existing devices such as Schottky-barrier diodes in these applications and thus warrant further development. Several modes of operation have been identified and include: self-oscillating mixers where the device due to its negative resistance generates power and is utilized as a mixer simultaneously; a video detector and mixer element which exhibits a negative resistance over a band of frequencies determined by the width of the depletion layer; and a conventional video detector and mixer element which does not exhibit a negative resistance but has a negligible series resistance due to the basic nature of the device. This leads to a detector and mixer element with an extremely high cut-off frequency and can lead to better performance than existing Schottky-barrier diodes. (Author)

The objectives of this investigation are to study the frequency conversion properties of punch-through semiconductor devices and to establish the frequency regions of their potential application as efficient detectors and mixers of information-bearing signals. The physics of two punch-through devices are studied in detail: the three-terminal punch-through transistor and the two-terminal BARITT (barrier injection transit-time) diode. The particle current injection process for both devices is examined and identified as simple diffusion over a potential barrier (exponential injection with respect to the barrier height). Dc and small-signal ac models for both punch-through structure are derived from standard bipolar junction transistor theory by applying a current-dependent, rather than the standard voltage-dependent, boundary condition for the minority carrier concentration at the collector edge of the low-field base region. The small-signal models include carrier transit-time effects in the diffusion-drift, reverse-biased regions of the devices by means of a transit-time factor similar to the factor used in the standard frequency domain analysis of pure saturated drift transit-time diodes. The small-signal noise properties of the BARITT diode are developed employing the same techniques used in the formulation of the BARITT diode circuit model. Both, small-signal impedances predicted by the circuit model and small-signal noise measures predicted by the noise analysis, compare very well with experimentally measured values of typical BARITT structures.

This is the Final Technical Report on subject contract whose objectives are to investigate theoretically and experimentally new solid-state phenomena and techniques having application to microwave generation, amplification and control. Tasks under this program are: Properties of IMPATT Diodes, Transverse Effects in IMPATT Devices, Pulsed IMPATT Diodes, Field-Effect Transistors, Experimental Field-Effect Transistor Investigations, IMPATT Diode Amplifiers, Controlled Avalanche Transit Time (CATT) Devices. (Author)

A two-dimensional finite-element simulation of a GaAs MESFET has been performed and a detailed final report completed. Results are shown for a lateral doping profile which reduces velocity saturation effects, thus improving performance. A procedure is described for fabricating the source and channel regions of a proposed vertical FET structure. Preliminary results are presented and discussed. Input and output matching circuits for a commercial JFET were designed by use of S-parameter based numerical techniques. Results of an experimental study of the first amplifier design are presented. Various methods for the measurement of frequency shift in pulsed oscillators have been studied. Work has begun on frequency shift measurements with pulsed TRAPATT oscillators. An investigation has been started to study the basic operating principles of controlled avalanche transit time (CATT) devices. The relative advantages and disadvantages are presented and discussed.

This is the fifth and sixth quarterly report under subject contract whose objectives are to investigate theoretically and experimentally new solid state devices and circuits for microwave duplication generation and control. Tasks under this program are: avalanche diodes (IMPATT and TRAPATT), field-effect transistors, self mixing BARITT diodes and applications of BARITT type structures. (Author)

This is the seventh/eight quarterly progress report on subject contract whose objectives are to investigate theoretically and experimentally new solid-state phenomena and techniques having application to microwave generation, amplification and control. Tasks under this program are: Properites of IMPATT Diodes, Transverse Effects in IMPATT Devices, Pulsed IMPATT Diodes, Field-Effect Transistors, Experimental Field-Effect Transistor Investigations, IMPATT Diode Amplifiers, Properties of BARITT Devices and Microwave Applications of BATITT-Type Structures. (Author)

The objectives of the program are to investigate theoretically and experimentally to verify the start-up transient behavior of the TRAPATT mode in both n- and p-type avalanche diodes. The investigation has involved three stages: (a) The development of a computer program which models with good accuracy the coaxial line currently in use in our laboratory; (b) The interaction of the above program with an already existing device program; and, (c) The investigation of the effect of pulse rise time on the turn-on behavior of the TRAPATT mode. Two basic studies were performed: (a) Theoretical Computer Study. This phase of the program has involved the development of a computer model which takes into consideration both the diode and the circuit properties. A particular current drive is assumed to exist and the interaction between the diode and circuit is evaluated thus resulting in the time-varying voltage wave shape developed across the diode. (b) Experimental Measurement of Transient TRAPATT Triggering Behavior. Detailed experiments have been executed to identify those mechanisms which participate in the turn-on characteristics of a TRAPATT device. The investigations have revealed the presence of numerous oscillations being present during the initiation of the TRAPATT mode. The various signals are identified, and it is demonstrated that the TRAPATT mode may be triggered by any one of the signals which are present.

During the 1960's the bipolar junction transistor (BJT) was making steady progress in operating in the low GHz range as the active device in linear amplifier systems. Now the state-of-the-art junction field-effect transistor (JFET), in particular the metal semiconductor FET (MESFET), promises to supplant the BJT for microwave operation while utilizing its inherent majority carrier device noise advantage. Although the JFET was investigated by Shockley in 1952, its development lagged that of the BJT due to fabrication difficulties. Present performance of the JFET has improved due to the ability of present technology to produce well-defined, narrow-gate devices (0.5 micrometers at present), since JFET performance is limited mostly by gate length. Speculatively, operation of the GaAs MESFET will be pushed toward operation at 50 GHz or greater with significant gain to allow MESFET cascades to be used for large gain at microwave frequencies.

The purpose of this investigation is to study theoretically and experimentally the operation of TRAPATT mode (an acronym for trapped plasma avalanche triggered transit) oscillators. The solid-state device and microwave circuit as well as the interaction between them are considered in detail. A simplified computer model of a TRAPATT oscillator that considers the operation of the device from the terminal voltage-current waveforms has been developed. This model allows the investigation of arbitrary current waveforms and therefore can be used in the study of harmonic tuning effects and the requirements for high-efficiency operation. The simplified computer model is used to study the operation of the oscillator with many different terminal voltage-current waveforms. Waveforms containing up to ten harmonic frequencies are considered. By individually varying the amplitude and phase angles of each harmonic component the optimum tuning conditions for high-efficiency operation are obtained. It has been determined that the oscillator efficiency is primarily dependent upon the amplitude and phase angle of the fundamental signal and the phase angle of the second-harmonic component. The amplitude of the second harmonic and the amplitudes and phase angles of the third and higher harmonic components have a significant effect on oscillator frequency but only a minor effect on oscillator efficiency. It has also been determined, theoretically at least, that steady-state TRAPATT oscillations are possible with single-frequency operation. (Author), Doctoral thesis.

The objectives of this program were to study the fundamental properties of semiconductor materials and devices and their utilization in microwave power generation, amplification, detection, and control and thus ultimately to improve the state of the art in microwave devices. Work was conducted in the following areas: IMPATT Devices, Properties of BARITT Devices, BARITT Device Fabrication and Results, Tunnel Transit-Time Devices, Baritt Varactors, and Video Detectors and Mixers Using BARITT Devices. (Author)

This is the third and fourth quarterly progress report on subject contract whose objectives are to investigate theoretically and experimentally new solid-state phenomena and techniques having application to microwave generation, amplification, and control. Tasks under this program are: Properties of IMPATT Diodes, Properties of TRAPATT Diodes, Field-Effect Transistors, Field-Effect Transistor Fabrication, IMPATT Diode Amplifiers and Experiments on TRAPATT Diodes., See also report dated Jun 74, AD-783 900.

The purpose of this study is to investigate the noise properties of IMPATT diodes as a function of device structure, material parameters and operating conditions; to determine the optimum noise performance which is achievable for IMPATT diodes when they are used as oscillators and amplifiers; to obtain an improved physical understanding of noise and its relationship to other important nonlinear properties such as the dc-to RF conversion efficiency and RF power generation of IMPATT devices; and to derive important design and operating criteria regarding noise, efficiency and power for oscillator and amplifier applications using IMPATT diodes. In order to achieve these goals, a comprehensive study of the noise properties of IMPATT diodes has been carried out., See also report dated Jun 74, AD-783 436.

The objectives of this study are two-fold. One is to develop a very general large-scale computer simulation model for semiconductor devices. The other is to simulate various Si avalanche diode structures operating in the IMPATT and TRAPATT modes at different operating conditions in order to investigate the effects of various parameters on the performance of these avalanche diodes., See also Volume 2, AD-A009 042.

An extensive simulation of the IMPATT mode of operation of two X-band Read-type diodes, ten X-band low-high-low diodes, four X-band one-sided abrupt diodes and two K-band realistic p-n junction diodes had been conducted for different bias current densities, frequencies, RF voltages and temperatures. The effects of various device parameters and operating conditions on diode performance have been investigated and discussed. A set of general guidelines for designing Si IMPATT diodes is presented. Simulations have also been done for the TRAPATT mode of operation of fourteen Si avalanche-diode structures at different frequencies and bias current densities. Effects of various device parameters and operating conditions on RF performance have been studied and discussed., See also Volume 1, AD-A009 041.

The purpose of the study is to investigate the operation of IMPATT diode oscillators with a variety of doping profiles and to compare the experimental operating results with those predicted from theory. In order to accomplish the objective, a method of diode fabrication was developed which allowed a variety of different diode structures to be fabricated and experimentally evaluated. Various experimental and computer techniques were used to characterize the diodes. These methods allow the diode impurity profile to be determined and indicate the thermal operating limits of the devices. The experimental work on the fabricated diodes with known impurity profiles is also described. Several differences in the operation of n(+)pp(+) and p(+)nn(+) diodes with varying structures are discussed and compared with theoretically predicted results.

The theorectical and experimental characteristics of BARITT and TUNNETT devices for use as millimeter-wave mixers and detectors were investigated. Theoretical calculations of BARITT conversion loss, noise figure, and RF and IF impedence levels were carried out. BARITT device fabrication was studied. Three BARITT structures, useful for frequencies between 35 and 95 GHz were fabricated and tested. BARITT devices were tested as mixers and detectors at 35 and 95 GHz. BARITTs were found to be useful millimeter-wave mixers or detectors. BARITT detector performance is comparable to more conventional detectors with TSS levels of - 48 dB per 1 MHz bandwidth and a dynamic range to 1-dB compression of 40 dB. The BARITT pulse burnout performance is superior to any conventional detector with a pulsed burnout level greater than 45 W. BARITT mixer performance is also comparable to Schottky-barrier mixers with conversion losses of 5 dB and 30 MHz noise figures of 6.8 dB. This performance, coupled with the high burnout level and ease of fabrication, makes the BARITT a useful millimeter-wave device. (Author), Prepared in cooperation with Microwave Associates, Inc., Burlington, MA.

The limitations and control of pulsed IMPATT diode millimeter-wavelength oscillators are described. A quasi-static oscillator model is established for characterizing amplitude and frequency behavior during pulsed operation in response to external influences such as bias current, temperature, optical injection, locking signal injection and RF circuit. The effect of these external parameters in oscillator turn-on, turn-off, frequency chirp during the pulse, and start-up jitter are given for a millimeter-wavelength oscillator using a Si double-drift diode. Methods of controlling the pulsed behavior including bias current compensation, optical compensation and injection locking are analyzed and applied to a pulsed millimeter-wave oscillator example. The optimum bias current and optical current waveforms which eliminate post turn-on frequency drift are presented. (Author)

This final report is a brief description of the work carried out under this program. In addition to the work reported here, several technical reports have been issued which describe in detail the work performed under this program. These reports are available and are considered as a part of this final report. The work carried out under this program included the following: properties of controlled avalanche transit-time (CATT) triode amplifiers, properties of high-efficiency X-band GaAs IMPATTs including single- and double-drift devices as well as CW and pulsed operation, power combining studies including fundamental and harmonic power combining, GaAs FET modeling, characterization and circuit studies, and development of a model to study the effects of energy and momentum relaxation effects on IMPATT device performance particularly at millimeter wavelengths. (Author)

The limitations and control of pulsed IMPATT diode millimeter-wavelength oscillators are described. A quasi-static oscillator model is established for characterizing amplitude and frequency behavior during pulsed operation in response to external influences such as bias current, temperature, optical injection, locking signal injection and RF circuit. The effect of these external parameters in oscillator turn-on, turn-off, frequency chirp during the pulse, and start-up jitter are given for a millimeter-wavelength oscillator using a Si double-drift diode.

The research is concerned with the investigation and utilization of various phenomena and techniques for the generation, amplification, detection and control of electromagnetic energy at microwave frequencies. The work is mainly oriented toward an investigation of the basic properties, capabilities and potential of: Avalanche transit-time devices including IMPATTs and TRAPATTs; Transferred-electron devices; Microwave field-effect transistors; Microwave integrated circuits.

A general noise theory has been developed for a nonlinear, self-oscillating device in a parallel G-L-C circuit. Variation of the nonlinear device admittance with both RF voltage and bias voltage is incorporated in the theory and the sources of noise are lumped into two equivalent noise generators: a video noise voltage generator and an RF noise current generator. The present study extends the work of Sweet by including the RF voltage dependence in the theory and by applying the theory to a quenched-mode admittance model of transferred-electron (TE) devices. The noise theory is used to study AM and FM TE oscillator noise as functions of load conductance, bias voltage, cavity tuning and carrier doping density for uniformly doped TE devices. (Modified author abstract), See also report dated May 73, AD-764 259.

The purpose of the study is to investigate the tuning and modulation properties of transferred-electron devices. The device performance under two basic tuning methods was examined: tuning through the bias voltage of the device and tuning through a resonant circuit. The tuning properties were derived from the interaction between the device and the circuit. Thus, both the device and the circuit admittances are needed for the investigation. Two conventional cavity circuits which were employed in these investigations, namely, the post-mount waveguide cavity and the slug-tuned coaxial-line cavity, had already been modeled and well understood. This study, therefore, concentrated on the nonlinear properties of the transferred-electron device. (Author)

This is the final report on subject contract whose objectives are to investigate theoretically and experimentally new solid-state phenomena and techniques having application to microwave generation, amplification, and control. Tasks under this program were: Modulation properties of Gunn-Effect Devices; Properties of IMPATT Diodes; High Efficiency Avalanche Diodes; Properties of TRAPATT Diodes; Field-Effect Transistors; Solid State Device Fabrication. (Author), See also AD-774 456.

Equations for the modulation products in the multi-signal analysis of an amplitude- and phase-modulated traveling-wave amplifier have been programmed and the results computed. The computation includes all three theoretical approaches derived and discussed in previous reports. These include the nonlinear approach using the two-signal input, the large-signal analysis using the multiple signal input and the Boltzmann transport equation approach using the multiple signal input. The output powers of some important cross-modulation components, the cross-modulation factors, etc. are presented in graphs. Experimental results using two and three signal inputs are presented for comparison. A large-signal analysis is carried out for a d-c pumped quadrupole amplifier employing cyclotronsynchronous wave interaction. Criteria for the validity of small-signal and large-signal analyses are established by means of the phase slip. Energy relations between the beam and the pumping field are discussed for a strong pumping field condition that would lead to the anomalous gain possibility. The technique for insertion of the helix-BeO rod into a metal envelope to improve the thermal conductivity of the assembly is developed. (Author)

A series of trajectory plots is shown which led to a reasonably good electrial design for the P mu = 20 gun. The work done on the electrostatically focused tube using a P mu=4.46 gun indicates that much better focusing can be obtained with the improved gun. At reduced voltages the beam transmission is only fair but it is shown that the percentage of transmission is improving as the design voltage is approached. In order to center the operating band of the 100-watt Crestatrons more nearly within the desired frequency range and in order to overcome the r-f losses observed in the couplers, a revision is made in the tube design. The new dimensions and electrical parameters are shown. (Author)

Research was continued on a development program on high-power 100-300 mc Crestatrons. The aim is to construct compact 100-watt Crestatrons employing permanent magnet focusing. Initially the tubes will be tested in a solenoid until they meet electrical specifications. Ultimately the permanent magnet focused tubes employing a de pressed potential collector will be ruggedized so as to meet environmental specifications. Theoretical as well as experimental studies on high perveance hollow-beam electron guns, in addition to electrostatic focusing systems were continued. The P Mu 20 hollow gun was programmed for solution on a digital computer. The electron trajectory plots obtained are described. The necessary steps to be taken in order to improve the gun performance are listed. A number of 100 watt Crestatrons were tested. Even though the saturation power output is still somewhat low, it is shown that the bandwidth as well as the conversion efficiency are satisfactory. The results of tapering the phase velocity of the slow-wave structure are described. A suggestion is made on how to take advantage of phase focusing near the tube output more fully.

Data on the electrostatic focusing system mounted in a beam analyzer is presented. For the voltages employed in the tests quite good transmission through the focusing structure has been observed. In addition rather complete data in the form of trajectory plots obtained from a digital computer program for the hollow-beam gun as well as the focusing system are presented. The hollow electron beam is shown to be focused quite well throughout the system. Work on the 100-300 mc metal-ceramic Crestatron is described. Some of the cold-test data obtained somewhat modifies the original calculations, but does not necessitate any design changes. The present status of tube construction is given.

The probe data obtained on the crossed-field stream analyzer are summarized. Detailed calcul tions on space-charge distribution and electron trajectories in a Kino crossed-field gun are analyzed. Some information on the relationship between beam laminarity and cathode width is presented for a flat cathode. The desirability of tilting the cathode is discussed. The determination of Kompfner dip conditions in an M-type amplifier is outlined along with nonlinear calculations on beating-wave gain. Additional experimental information on the S-band crossed-field amplifier was obtained and a new electron gun design is outlined. The analysis of noise generation and propagation in crossed-field devices is treated using both a density function method and a Monte Carlo calculation. Calculations of spacecharge density and potential distributions in planar devices are given. An outline of the design of the experimental noise analyzer is presented. (Author)

The purpose of this investigation is to study the noise transport and reduction phenomena in multi velocity electron beams with significant potential variations in the transverse direction. Correlations between the noise reduction mechanism and the multi-dimensional nature of the electron beams are sought. The investigation was carried out by means of a high-speed digital computer employing two different numerical methods. The mathematical model assumes an infinite confining magnetic field so that transverse motions are not allowed. In addition a one-dimensional half Maxwellian velocity distribution function is considered for the electrons at the potential minimum. Details of the derivation of a small signal linearized Boltzmann equation in terms of a statistical electron density function and the electric field in a two- dimensional space-charge limited diode are presented, together with some discussion on the singularities in the boundary conditions and the formulation of the a-c electric fields. To facilitate a solution of the transport equation, velocity classes are introduced as an approximation so that digital techniques become applicable. Haus's noise theory for small-signal longitudinal beam devices is employed to evaluate the noise transport characteristics of the two-dimensional electron beam., Doctoral thesis.

In the electrostatic focusing system employing the P micron 4.46 hollow-beam gun it is shown that a substantial portion of the observed beam interception is due to secondary electrons. One method of reducing this effect is shown. Scaling the P micron 4.46 gun to a value of 20 is de scribed. Two 100-watt Crestatrons were tested at reduced power due to a poor r-f match in the first tube and to high beam interception in the second tube. It is apparent from the data, however, that most of the design objectives have already been easily met. These are a full 3 to 1 band width under small-signal as well as saturation conditions, more than enough small-signal gain and quite encouraging values of conversion efficiency.

This report summarizes the work done to date on the general program of applied research in microwave and quantum electronics. All the investigations carried out are directed toward ex tending the state of the art in microwave and quantum electronics. The research is theoretical as well as experimental in nature. The theoretical work is largely devoted to an investigation of low-noise phenomena and beam-plasma interactions. The experimental work is concerned with electromagnetic generation, particularly in the short wavelength regions. This includes several plasma devices, masers, and a Cerenkov radiation device. In addition crossed field electron guns and high- thermal-conductivity dielectric materials for high-average-power microwave tubes are studied from a theoretical as well as experimental point of view.

The effect of several kinds of nonuniformities in the circuit phase velocity and beam potential on the start-oscillation conditions of an O-type BWO were investigated. The nonuniformities include linear, quadratic and exponential circuit phase velocity tapers and linear, quadratic, exponential and sinusoidal voltage gradients. It is shown that under certain conditions the taper may be employed to either reduce the startoscillation current or to suppress backward-wave oscillations in forward-wave amplifiers. Circuit phase velocity tapers for achieving phasefocusing and thus enhancing the efficiency of O-type BWO's are derived. Employing such a circuit taper in an experimental S- band BWO resulted in efficiency improvement factors of 1.2 to 2.0 to 1.0 over a frequency range of 2.0 to 4.0 gc. Efficiency enhancement through utilization of multisegment depressed collectors is investigated. Optimum collector segment voltages for achieving optimum efficiencies under typical operating conditions were determined and are presented. The utilization of prebunched beams in BWO's is considered and the effect on the start-oscillation conditions and efficiency is determined., Doctoral thesis.

This is the fourth quarterly report on subject contract whose objectives are to investigate theoretically and experimentally new solid-state phenomena and techniques having application to microwave generation, amplification, and control. Current tasks under this program are the following: High-power Gunn-effect devices; gunn-effect amplifiers; modulation properties of gunn-effect devices; avalanche-diode amplifiers; high-efficiency avalanche diodes; nonlinear operating characteristics of IMPATT diodes; solid-state device fabrication; and, instabilities in germanium., See also AD730636.