CW Magnetron Research Articles

A microwave discharge in high-velocity flows initiated by a half-wave antenna

A microwave discharge in high-velocity (150—250 m/s) air flows induced on a half-wave vibrator is studied. A cw magnetron microwave generator with a frequency of 2.45 GHz and an output power of up to 5 kW was used for initiation of the microwave discharge. The high-speed video imaging was used for studying the discharge structure, determining the diameter and length of the plasma channel as a function of flow velocity and pressure. Electron concentration and temperature, along with characteristic gas temperature, were determined based on the optical spectra. The possibility of using this microwave discharge for ignition of hydrocarbon–air mixtures in combustion chambers of ramjet engines is proved experimentally.

On forced RF generation of CW magnetrons for accelerators

CW magnetrons, initially developed for industrial RF heaters, were suggested to power RF cavities of superconducting accelerators due to their higher efficiency and lower cost than traditionally used klystrons, IOTs or solid-state amplifiers. RF amplifiers driven by a master oscillator serve as coherent RF sources. CW magnetrons are regenerative RF generators with a huge regenerative gain. This causes regenerative instability with a quite large noise when a magnetron operates with the anode voltage above the threshold of self-excitation. Traditionally, an injection locking by a small signal is used for stabilization of magnetrons. In this case CW magnetrons with the injection-locked oscillations generate a high level of noise. This may preclude use of standard CW magnetrons in this operating mode in the Superconducting RF (SRF) accelerators. In this article we described a method developed for forced RF generation of CW magnetrons when the magnetron startup is provided by the injected forcing signal and the regenerative noise is suppressed. The method is most suitable for powering high Q-factor cavities.

Particle-In-Cell Simulations of High Efficiency 12-Vanes 2.45 GHz Continuous Wave Magnetron

As an essential vacuum electronic device for producing the microwave, the magnetron has various applications. This study developed a novel high-efficiency 12-vanes CW magnetron and anode resonance system that improved mode separation, expanded the working space of π-mode and made other modes more challenging to trigger, ultimately eliminating the possibility of mode jumping. A magnetron was simultaneously supplied with a particular quantity of anode voltage, and the cathode was generated by the electron, and high-frequency field interaction of a homogeneous magnetic field. The work efficiency of the 12-vanes CW magnetron was significantly enhanced. Given an anode voltage of 8000 V and a magnetic flux density of 3980 Gs as a consequence of particle simulation, the variation trend of a magnetron’s output power oscillation curve correlated with the development of hexagonal spokes. After a period of stable operation, the magnetron’s fundamental parameters were determined to be as follows: the primary frequency oscillation frequency was 2.466 GHz, the anode collision current was 1.08 A, the amplitude of sinusoidal oscillation was 125, the output power was 7812.5 W, and the corresponding power conversion efficiency was 90.42%. Changing the magnitude of the anode voltage or magnetic flux density resulted in a reduction in power conversion efficiency within a particular range; however, between 85% and 90% stability was maintained.

Utilization of the CW magnetrons as coherent RF sources for superconducting RF accelerators

CW magnetrons designed and optimized for industrial heaters, driven by an injection-locking signal, were suggested to power Superconducting RF (SRF) cavities. However, the CW magnetrons, which are regenerative generators, are intended to operate in self-excitation mode, so, for reliable starting they use a large regenerative gain, causing a large regenerative instability in operation. Thus, power supply ripple, even shot noise, etc., lead to multiple sidebands forming a quasi-continuous noise spectrum at the carrier frequency. Therefore, in the traditionally used mode of operation and control, such magnetrons are inapplicable for powering high Q-factor SRF cavities. A new approach to operation and control of CW magnetrons considering non-stationary processes during start-up and operation makes it possible to find a mode of almost coherent RF generation of tubes with a significant reduction in regenerative instability and noise and increased efficiency. In our work is presented substantiation for the newly developed mode with an analysis of the new approach based on experimental results.

Selection of technologies for metal film application using physical deposition techniques

Introduction. Obtaining high-quality thin metal films is important for advances in the technologies of applying antifriction and wear-resistant coatings on cutting tools or parts of friction couples. Various techniques of physical film deposition are applied using technologies of cathode (ion), magnetron and ion beam assisted sputtering. The work objective is to analyze, compare and determine the feasibility of techniques for the physical deposition of thin metal films when applying antifriction and wear-resistant coatings on cutting tools or parts of friction couples. Materials and Methods. Technologies of cathode (ionic), magnetron and ion-beam sputtering are considered. Schematic diagrams, conditions and parameters of the considered processes are presented. Results. An advanced technology for the deposition of thin films, alloying and hardening of the surfaces of metal parts is magnetron sputtering. Continuous wave (cw) magnetrons are used to apply coatings of complex composition or multilayer coatings on flat substrates. Ion beam sputtering is considered a slow sputtering of the target surface by bombardment with a high-energy ion beam and deposition on the substrate surface. Under the ion implantation, the surface of metals is doped with recoil atoms, which receive high energy from accelerated ions and move a few nanometers deeper. This enables to obtain ultra-thin doped layers. Low temperature of ion implantation, the possibility of sufficiently accurate control of the depth and the impurity distribution profile, create the prerequisites for the process automation. Wear tracks are more acidified under the same wear conditions on implanted steel compared to non-implanted steel. The nonequilibrium process under ion implantation causes the formation of such alloys in the surface layers that cannot be obtained under normal conditions due to diffusion of components or limited solubility. Ion implantation makes it possible to obtain alloys of a certain composition in the surface layer. Surface properties can be optimized without reference to the bulk properties of the material. Implantation is possible at low temperatures without a noticeable change in the size of the product. Discussion and Conclusion. Cathode (ion), magnetron and ion-beam sputtering have common advantages: due to the relatively low temperature, the substrate does not overheat; it is possible to obtain uniform coatings; the chemical composition of the deposited coatings is accurately reproduced. The rest of the advantages and disadvantages of the considered methods are individual. The results can be used to create thin films through alternating magnetron and then ionbeam deposition processes, which enables to obtain films uniformly modified in depth. This is important in the production of parts of friction couples and cutting tools to improve their quality.

Efficiency Enhancement of CW Magnetron by Ferrite Material Filling

This paper presents the output performance enhancement study of a strapped vane 2.45-GHz industrial magnetron in the presence of a ferrite material. A 3-D particle-in-cell code, CST Particle Studio, has been used to examine the output performance (output power, anode current, efficiency, and hot frequency) of a 10-kW continuous wave ten vane magnetron with its alternate resonators partially filled with Yttrium iron garnet (YIG). Saturated efficiency and output power enhancements of 7.25% and 13.75%, respectively, were found for a filling factor of 33.68%. It has also been found that YIG filling reduces the operating $\pi $ -mode frequency reaching as high as 10% of the unfilled case for about 30% filling. Method has been suggested to compensate for it.

An efficient magnetron transmitter for superconducting accelerators

A concept of a highly-efficient high-power magnetron transmitter allowing wide-band phase and the mid-frequency power control at the frequency of the locking signal is proposed. The proposal is aimed for powering Superconducting RF (SRF) cavities of intensity-frontier accelerators. The transmitter is intended to operate with phase and amplitude control feedback loops allowing suppression of microphonics and beam loading in the SRF cavities. The concept utilizes injection-locked magnetrons controlled in phase by the locking signal supplied by a feedback system. The injection-locking signal pre-excites the magnetron and allows its operation below the critical voltage in free run. This realizes control of the magnetron power in an extended range (up to 10dB) by control of the magnetron current. Experimental studies were carried out with 2.45GHz, 1kW, CW magnetrons. They demonstrated stable operation of the magnetrons and the required range of power control at a low noise level. An analysis of the kinetics of the drifting charge within the framework of the presented model of phase focusing in magnetrons substantiates the concept and the experimental results.

Review of Magnetron Developments

AbstractMagnetrons have been the most efficient high power microwave sources for decades. In the twenty-first century, many of the development works are headed towards the performance improvement of CW industrial magnetrons. In this review article, the development works and techniques, used on different types of magnetrons, for the performance enhancement in the past two decades have been discussed. The article focuses on the state of the art of CW magnetron and the direction it will take in foreseeable future. In addition it also glimpses some of the major variants of magnetron which have further opened up scope in mm-THz spectrum of electromagnetism.

A multichannel power supply for high power magnetrons

The paper describes characteristics and design principles of a multichannel power supply for CW magnetrons with RF power up to 3 kW. An advanced control system implemented in the power supply has resulted in its good operational properties as well as allowed providing adaptive procedures for the regulation of magnetron operation. A modular approach based on utilization of novel electronic components increases reliability and lowers weight and dimensions of the power supply.

Frequency and phase modulation performance of an injection-locked CW magnetron

It is demonstrated that the output of a 2.45-GHz magnetron operated as a current-controlled oscillator through its pushing characteristic can lock to injection signals in times of the order of 100-500 ns depending on injection power, magnetron heater power, load impedance, and frequency offset of the injection frequency from the natural frequency of the magnetron. Accordingly, the magnetron can follow frequency and phase modulations of the injection signal, behaving as a narrow-band amplifier. The transmission of phase-shift-keyed data at 2 Mb/s has been achieved. Measurements of the frequency response and anode current after a switch of phase as a function of average anode current and heater power give new insight into the locking mechanisms and the noise characteristics of magnetrons

Noise Performance of Frequency- and Phase-Locked CW Magnetrons Operated as Current-Controlled Oscillators

Low-power continuous wave cooker magnetrons driven from industrial-quality switch-mode power supplies have been frequency locked by driving them as current-controlled oscillators in a phase-lock loop (PLL). The noise performance of these frequency-locked oscillators is reported as a function of heater power. The injection of -30- to -40dB signals derived from the reference oscillator of the PLL into the magnetron's output waveguide while the anode current is controlled by the PLL is shown to phase lock the magnetron's output. Results for locking performance are presented.

Electron cyclotron resonance heating in a short cylindrical plasma system

Electron cyclotron resonance (ECR) plasma is produced and studied in a small cylindrical system. Microwave power is delivered by a CW magnetron at 2.45 GHz in TE10 mode and launched radially to have extraordinary (X) wave in plasma. The axial magnetic field required for ECR in the system is such that the first two ECR surfaces (B = 875.0 G andB = 437.5 G) reside in the system. ECR plasma is produced with hydrogen with typical plasma density ne as 3.2 × 1010 cm-3 and plasma temperature Te between 9 and 15 eV. Various cut-off and resonance positions are identified in the plasma system. ECR heating (ECRH) of the plasma is observed experimentally. This heating is because of the mode conversion of X-wave to electron Bernstein wave (EBW) at the upper hybrid resonance (UHR) layer. The power mode conversion efficiency is estimated to be 0.85 for this system. The experimental results are presented in this paper.

Plasmatron with Microwave Excitation of Nonequilibrium Plasma

Testing results of a microwave plasma generator (plasmatron) intended for excitation of a strongly nonequilibrium plasma arepresented. Nonequilibrium properties of the plasma are described in detail.The plasma flame is formed at an open end of a coaxial line under atmospheric pressure. Argon is used as plasma forming gas, and a 10 GHz CW magnetron with 10 W output power is used for plasma excitation.The efficiency of absorption of microwave power in the plasma is higher than90% with specific absorbing capacity of 0,4.4 kW/cm3

Switch Mode Power Supply for Microwave Heating Based on the Boucherot Effect

This paper describes anew self-resonating switch-mode power-supply for driving CW magnetrons, based on the Boucherot effect. A detailed circuit analysis is given and its performance is evaluated for an 800W/2450MHz magnetron, whilst work at high power driving a magnetron up to 40kW is reported.A comparison of the supply with the conventional power-supply used in microwave ovens is made and the principal features of the new design are found to be: low energy dissipation under short-circuit conditions, low ripple current and voltage waveforms that result in more precise control in the range 20–100% of rated power, high efficiencies and small size and weight.

High‐power (500‐kW) CW magnetron for microwave heating

High‐power (500‐kW) CW magnetron for microwave heating

マイクロ波加熱用大電力(500kW)マグネトロン

マイクロ波加熱用大電力(500kW)マグネトロン

Simple low-cost microwave plasma source

A generator-cavity system is described which is capable of delivering 0–600 W of microwave power at 2.45 GHz. The power generating section has been constructed from components contained in a portable home microwave oven and the cavity was assembled from easily machinable pieces. The cw magnetron source was mounted directly on a cylindrical microwave cavity. The plasma was contained in an on-axis 20-mm o.d. quartz tube. Design tradeoffs and operating information are discussed.

A young engineer enters the microwave tube field during world war II

The author describes his wartime experience at the General Electric Research Laboratories, developing CW magnetrons for countermeasures, at the same time as others were developing the pulse magnetron for radar transmitters.

Design of the Axial Output Structure of the CW Magnetron

The axial output structure of the CW magnetron is divided into four regions. The concept of matching between regions is introduced, and a method of analysis for each region is presented. The requir...

100 kW, 915 MHz CW Magnetron for INdustrial Heating Application

AbstractIn this paper the design and operating features of a newly developed 100 kW CW magnetron are described. The magnetron has been successfully used as a high power microwave source in an applicator for breaking concrete or rocks by microwave power.