Extended Interaction Klystron Research Articles

Mode stability analysis in the beam—wave interaction process for a three-gap Hughes-type coupled cavity chain

Based on space-charge wave theory, the formulae of the beam—wave coupling coefficient and the beam-loaded conductance are given for the beam—wave interaction in an N-gap Hughes-type coupled cavity chain. The ratio of the non-beam-loaded quality factor of the coupled cavity chain to the beam quality factor is used to determine the stability of the beam—wave interaction. As an example, the stabilities of the beam—wave interaction in a three-gap Hughes-type coupled cavity chain are discussed with the formulae and the CST code for the operations of the 2π, π, and π/2 modes, respectively. The results show that stable operation of the 2π, π, and π/2 modes may all be realized in an extended-interaction klystron with the three-gap Hughes-type coupled cavity chain.

Elimination of speckle and target orientation requirements in millimeter-wave active imaging by modulated multimode mixing illumination

Active imaging can provide significantly larger signal margins in the millimeter-wave spectral region than passive imaging, especially indoors-an important application for which there is no cold sky illumination. However, coherent effects, such as speckle, negate much of this advantage by destroying image clarity and target recognition. Moreover, active imaging demonstrations often use strategically chosen target orientations to optimally reflect power from the active illuminator back to the imaging receiver. In this paper we will discuss and show experimental results for a new active imaging approach that largely eliminates coherent effects and the need for optimized target orientation. The work described uses a synthesized harmonic multiplier chain to drive a 5 W extended interaction klystron at 218.4 GHz, a mechanical mode mixer to illuminate and modulate many modes, and a heterodyne receiver coupled into a 60 cm scanning mirror. Large signal margins were obtained in this ~50 m range work, showing paths to imaging at ~1 km, imaging with considerably less powerful illuminators, and the use of focal plane arrays.

Simulation and design of a W-band extended interaction klystron amplifier

Extended interaction klystron amplifier is a very important high power millimeter wave source with many actual and potential applications. Based on the electromagnetic simulation software and 3D PIC code, a W-band extended interaction klystron amplifier is designed. In the PIC simulation, when the beam voltage is 30 kV and current is 8 A, the device can generate a 43 kW output power at 96.8 GHz with an efficiency of 18% and a gain of 49.3 dB.

DESIGN ON KA-BAND FILTER LOADED THREE-GAP COUPLED OUTPUT CAVITIES

The extended interaction klystron(EIK) consists of several reentrant multi-gap coupled cavities.The demand for high-power microwave sources in the millimeter-wave region promotes the development of a Ka-band extended interaction klystron(EIK).In this study,the real part of the impedance of the three-gap coupled output cavities composed by three uniform gap cavities was derived by using the equivalent circuit theory and field analysis method,respectively.The basic parameters of the broad band output circuit were obtained by using equivalent circuit theory.Filter loaded three-gap coupled output cavities with band width of 4.6% were designed by using field analysis method.It lays a solid foundation for the development of the broad band EIK.

Six-Port Interferometric Technique for Accurate $W$-Band Phase-Noise Measurements

An innovative six-port (SP) phase-noise measurement technique for millimeter-wave high-power sources is proposed in this paper. Simulation results using a 94-GHz rectangular waveguide SP circuit model validates the measurement principle for both millimeter-wave oscillators and amplifiers. Phase-noise measurement results of a 100-W extended interaction Klystron amplifier are presented and discussed. Compared to conventional methods, this new method allows accurate low-cost phase-noise measurements.

State-of-the-Art W-Band Extended Interaction Klystron for the CloudSat Program

This paper reviews the National Aeronautics and Space Administration (NASA)/Jet Propulsion Laboratory (JPL) CloudSat Extended Interaction Klystron requirements, design, performance, and development of a long life model for the European Space Agency (ESA)/Japan Aerospace Exploration Agency EarthCARE program plus Ka-band Extended Interaction Klystrons for the NASA/JPL Jupiter Icy Moons Orbiter and ESA European Global Precipitation Measurement Missions.

Pulsed ESR at 140 GHz

AbstractWe report pulsed electron spin resonance (ESR) experiments at a static magnetic field (B0) of 5.0T, corresponding to a microwave frequency of ˜140 GHz for g = 2 electrons. The experiments were performed with a transmission spectrometer, utilizing a 300 watt extended interaction klystron (EIK) operating in pulsed mode, together with a crossed waveguide Fabry‐Perot resonator which provided 30–40 dB of receiver isolation. Signal averaging was accomplished by mixing the pulse from the EIK with a 139.95 GHz reference oscillator, which was subsequently mixed with a local oscillator to generate a trigger signal for a digital oscilloscope. Concurrently, the ESR signal was mixed to an intermediate frequency using a second low frequency oscillator which was phase‐locked to the same source as the trigger oscillator and detected with a transient digitizer. In this configuration we achieved π/2 pulses of −14 ns, and the isolation of the Fabry‐Perot provided short spectrometer dead times (20–50 ns, including the pulse) for subsequent detection of the free induction decays. The performance of the spectrometer is demonstrated with spectra obtained from crystals of fluoranthenyl hexafluorophosphate.

Higher order modes and instabilities in coupled-cavity TWT's

Laboratory records available to the authors, dating back to 1975, report several test CCTWT's troubled by an uncommon trapped oscillation, explained as a tube section operating as a multigap monotron or extended-interaction klystron (EIK) involving a higher order mode of the interaction circuit. Antisymmetric RF field distributions for these modes tend to make the section a resonator with little external coupling at multiple close-spaced frequencies. All varieties of CCTWT interaction circuit are equally able to support such modes and the list of problem tubes inculpates no type or feature of the circuit per se (as opposed to beam conductance, which was relatively prominent in all). RF fields and propagation characteristics for these modes are discussed in three categories of interaction circuit. When the tube is designed for a given performance as a TWT (based on the conventional mode), parameters such as beam conductance and circuit length and loss combine to determine gain through the well-known TWT relationships. The fact that these parameters combine under very different relationships as regards potential oscillation as an EIK involving a higher order mode, however, helps explain why fairly similar tubes are not all troubled by the instability in question. Since conventional one-dimensional analytic approaches are inadequate for modeling beam interaction with antisymmetrically distributed RF fields, fully three-dimensional modeling capability is looked to as the analytic tool needed to evaluate CCTWT designs (and corrective changes when necessary) relative to the instability discussed.

The development of a 100-kW CW X-band extended-interaction klystron having an exceptionally large bandwidth

The objectives of the development program to be described are an output power of 100-kw CW at 8 GHz, an efficiency in excess of 30%, and an instantaneous 3-dB bandwidth in excess of 3%. The design chosen was an extended-interaction klystron (EIK) with a three-gap 2π-mode output resonator. A two-gap uncoupled cavity pair was chosen as the penultimate resonator. The cavity pair was utilized to maintain greatest attainable efficiency over the entire bandwidth of the tube. Conventional tunable single-gap resonators were used in the low level buncher portion of the tube.

An extended-interaction klystron: Efficiency and bandwidth

A three-cavity extended-interaction klystron, with cavities consisting of resonated sections of ring-bar structure, was tested in pulsed operation near 25 kV at 1100 Mc/s. The active length of the output resonator was variable between one and five resonant half wavelengths. The input and the intermediate cavities were tuned continuously to simulate a wide-band stagger-tuned bunching section. The dependence was investigated of the efficiency and the saturated bandwidth on the length and the loading conditions of the output resonator, and on the beam velocity. Data are presented which lead to the following conclusions: As the cavity length is increased, the peak efficiency rises up to a point and then remains constant, while the bandwidth increases proportional to cavity length. As the loading is reduced, for a given cavity length, the efficiency generally rises monotonically until further reduction in loading results in the onset of regenerative cavity oscillations at the frequency of the design resonance. The necessary suppression of regenerative oscillation in adjacent resonances becomes more difficult as the cavity length is increased, and a basic limitation on cavity length is given by the quality of the coupler, which must be capable of providing uniform and heavy loading over a broad frequency range.

A two-cavity extended interaction klystron yielding 65 per cent efficiency

Results of experiments with a two-cavity extended interaction klystron are given. The tube is nominally capable of 1 kw-CW at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</tex> band and consists of two five-gap short-slot-coupled cavities coupled to the input and output lines by means of TWT matching sections with adjustable mismatches. The unusual features of the tube are 1) the length of extension of the resonant cavities (five electron ballistic wavelengths) and 2) the incorporation of different and controllable beam-circuit synchronism conditions for the input and output cavities. The results of principal interest are the low velocity spread in the spent beam entering the collector providing high total conversion efficiency (65 per cent) with collector depression and stable gain in excess of 15 db. Some treatment of the relationship of efficiency and oscillation stability is included, as well as comments on the usefulness of such a design for high power millimeter wave amplification.