Magnetron Diode Research Articles

Comparison of the output spectrum for four models of devices with crossed fields

This paper considers four models of crossed-field devices: cylindrical magnetron, cylindrical magnetron diode, planar magnetron diode and planar magnetron. As is known, in crossed-field devices electrons move by cycloid-like trajectories and induced current arises. The spectral components of the induced current for every of the models are calculated. It has been found that the components of the induced current spectrum contain from one (planar magnetron diode) to eight (cylindrical magnetron diode) components. The calculated spectral components have been compared to the spectral components of the generation spectrum of the real device.
 Only one component whose frequency coincides with the cyclotron frequency was found in the induced current spectrum of the planar magnetron diode.
 The induced current spectrum in a planar magnetron has three components. These frequencies have a large difference with the frequency of magnetron generation for a microwave oven. Therefore, the models of the planar magnetron diode and the planar magnetron are not very suitable for simulating the operation of crossed-field devices.
 The induced current spectrum in a cylindrical magnetron diode contains eight components. The third harmonic is closest to the fundamental frequency of the microwave magnetron. In this case, the difference between the frequencies being compared is near 10 %. Therefore, the model of a cylindrical magnetron diode is not very suitable for modeling the operation of crossed-fields devices.
 Two components were found in the induced current spectrum of a cylindrical magnetron. The first harmonic is the closest to the fundamental frequency of the microwave magnetron. In this case, the difference between the frequencies being compared does not exceed 3 %. Such a small discrepancy between the calculated and real frequencies can be explained by the presence of a spatially periodic distribution of the electrostatic field. Thus, the cylindrical magnetron model is well suited for simulating the operation of crossed-fields devices.

Design and experimental results of a 28 GHz, 400 kW gyrotron for electron cyclotron resonance heating

A high-power 28 GHz gyrotron has been successfully developed at the Institute of Applied Electronics, China Academy of Engineering Physics. This gyrotron was designed for electron cyclotron resonance heating (ECRH) in the spherical tokamak XL-50. A diode magnetron injection gun was designed to produce the required gyrating electron beam. The gyrotron operates in the TE8,3 mode in a cylindrical open cavity. An internal quasi-optical mode converter was designed to convert the operating mode into a fundamental Gaussian wave beam and separate the spent electron beam from the outgoing microwave power. A tube has been built and successfully tested. The operational frequency of the tube is 28.1 GHz. For beam parameters at an accelerating voltage of 71 kV and beam current of 16 A, the gyrotron has delivered an output power of 400 kW, with a pulse length of 5 s. The output efficiency is about 50% with a single-stage depressed collector. The gyrotron has been installed on the XL-50 and has played an important role in the ECRH experiments.

Design and Analysis of a Diode Magnetron Injection Gun for a G-Band Gyro-TWT

A diode magnetron injection gun (MIG) has been designed and analyzed for G-band gyro-traveling wave tube (Gyro-TWT). A novel curved surface emitter is proposed to enhance the beam quality. An electron beam with velocity ratio of 1.20 and transverse velocity spread of 2.11% is obtained. The beam transportation stability with geometry misalignment is also analyzed, and the assembly accuracy should be controlled under 0.1 mm. The stray electron is intercepted by the capture structure to avoid the bombardment to the interaction circuit. Then the cathode is fabricated, and the temperature distribution is measured. The experimental result matches well with the simulation. The electron beam quality considering expansion, surface roughness, and thermal emission is estimated, and the total transverse velocity spread is about 2.63%.

Operation parameters of magnetron diode for high-rate deposition of aluminum films

This article reports on the results of the detailed study of erosion of Al target in magnetron discharge plasma. It was demonstrated that the combination of middle-frequency (MF) and high impulse power (HiPIMS) power supply results in the significant increase of deposition rates of Al films by changing of sputtering yield. The MF pulse assists HiPIMS discharge to transit in a high power mode.

Effect of target power on the physical properties of Ti thin films prepared by DC magnetron sputtering with supported discharge

AbstractThe present paper describes the effect of target power on the properties of Ti thin films prepared by DC magnetron sputtering with (triode mode) and without (diode mode) supported discharge. The traditional diode magnetron sputtering with an addition of a hot filament has been used to sustain the discharge at a lower pressure. The effect of target power (60, 80, 100 and 120 W) on the physical properties of Ti thin films has been studied in diode and triode modes. XRD studies showed that the Ti thin films prepared at a target power up to 100 W in diode mode were amorphous in nature. The Ti thin films exhibited crystalline structure at much lower target power of 80 W with a preferred orientation along (0 0 2) plane. The grain size of Ti thin films prepared in triode mode increased from 64 nm to 80 nm, whereas in diode mode, the grain size increased from 2 nm to 5 nm. EDAX analysis confirmed that the incorporation of reactive gases was lower in triode mode compared to diode mode. The electrical resistivity of Ti thin films deposited in diode mode was found to be 85 µΩ⋅cm (target power 120 W). The electrical resistivity of Ti thin films in triode mode was found to be deceased to 15.2 µΩ⋅cm (target power 120 W).

Research of TiZrV Pumping Coatings on the Inner Walls of Vacuum Chamber

Abstract In order to coat TiZrV alloys on the inner-surface of slender vacuum pipe of accelerator, a set of DC (Direct-Current) diode magnetron sputtering system was set up through calculation. After sputtering deposition, it translates the vacuum pipe from gas source into a pump. The test results show that the ultimate pressure is lower and the problem of big pressure gradient distribution is solved after TiZrV NEG coating.

The magnetron method for the determination of e/m for electrons: revisited

Additional information concerning the energy distribution function of electrons in a magnetron diode valve can be extracted. This distribution function is a manifestation of the effect of space charge at the anode. The electron energy distribution function in the magnetron is obtained from studying the variation of the anode current with the magnetic field in the region when the current starts to fall with increasing magnetic field. This region has not received much interest so far.

Sputtering of the magnetron diode target in the presence of an external ion beam

The effect of an external ion beam on the plasma and target of a dc magnetron sputtering system in the course of reactive deposition of films is investigated. A combined experimental setup consisting of a magnetron diode and a hall-current ion source is constructed. The influence of a fast ion beam on the discharge current formation, the target emission characteristics, and the target etching rate is considered. It is shown that the ion assistance expands the operating range of the magnetron diode, increases the deposition rate, and substantially shortens the target training time. At the same time, it practically does not affect the ionization processes in the plasma.

Entropy, Information, and Complexity of the Steady States of Open Systems Not Satisfying the Principle of Local Equilibrium

The entropy of the steady state of an open electronic system is determined, and its relation to the entropy arriving at the environment is established. The notion of system ordering is defined, and quantitative parameters characterizing ordering are introduced. The information and conditional complexity of the system versus the state of thermodynamic chaos are determined. These values are numerically estimated for vacuum, magnetron, and Gunn diodes.

Electron self-organization in electronic devices

The open systems, which contain a huge number of electrons supplied from outside along with the energy, are described by a functional that takes into account the Lagrangians of all particles and is called the integral Lagrangian. A nonextremal principle is formulated that postulates that the value of this functional decreases as the system approaches the steady state. The principle is extended to the systems occurring near thermodynamic equilibrium (where it is virtually equivalent to the principle of minimum energy dissipation), as well as to the nonlinear systems, including those in which the motion of particles is described by equations of classical mechanics. The applicability of the principle is demonstrated by the examples of a vacuum diode, magnetron diode, and Gunn diode.

Search for new materials in sputtered V 1− xC x films

In this work, the vanadium–carbon system has been explored in a wide range of atomic carbon content x (0.01< x<0.69) with the aim of obtaining films of new materials. V 1− x C x films were prepared by reactive dc diode magnetron sputtering and Electron Probe Micro-Analysis (EPMA) was used to determine their composition. The structures of as-sputtered films were identified by X-ray and Transmission Electron Microscopy (TEM). It is shown that they strongly depend on the carbon content x and several interesting facts can be underlined. If most of the films are crystalline and contain phases related to the phase diagram, a glass forming ability (GFA), located around x=0.32, permits to obtain a mainly amorphous film. This value is in the carbon content range of the hemicarbide V 2C. Below x=0.32, films are composed of the bcc vanadium solid solution which can be considerably extended (up to 0.17) inducing a lattice parameter expansion. Above x=0.32, films are first wholly made up of the substoichiometric VC monocarbide and then contain additional amorphous carbon. For x=0.32, TEM images and associated diffraction patterns suggest a nanocomposite material with numerous little crystals of carbide embedded in an amorphous matrix. A special attention has been devoted to this composition and a crystallization study has been undertaken. All these results show the capability of the binary V–C system combined with a sputtering process to generate promising films and coatings.

Dynamics of magnetic insulation failure and self-organization of an electron flow in a magnetron diode

The dynamics of back cathode bombardment (BCB) instability in a magnetron diode (a coaxial diode in a magnetic field, B ≡ B0z ≡ B0) is numerically simulated. The quasi-stationary regime of electron leakage across the high magnetic field (B0/Bcr > 1.1, where Bcr is the insulation critical field) is realized. An electron beam in the electrode gap is split into a series of bunches in the azimuthal direction and generates the electric field component Eθ(r, θ, t), which accelerates some of the electrons. Having gained an extra energy, these electrons bombard the cathode, causing secondary electron emission. The rest of the electrons lose kinetic energy and move toward the anode. Instability is sustained if the primary emission from the cathode is low and the secondary emission coefficient kse=Ise/Ie, BCB is greater than unity. The results of numerical simulation are shown to agree well with experimental data. A physical model of back-bombardment instability is suggested. Collective oscillations of charged flows take place in the gap with crossed electric and magnetic fields (E × B field) when the electrons and E × B field exchange momentum and energy. The self-generation and self-organization of flows are due to secondary electron emission from the cathode.

A 35-ghz low-voltage third-harmonic gyrotron with a permanent magnet system

A systematic theoretical and experimental study on a 35-GHz 45-kV third-harmonic gyrotron with a permanent magnet system is presented in this paper. A complex cavity with gradual transition and a diode magnetron injection gun (MIG) are employed in the gyrotron. A self-consistent field nonlinear theoretical investigation and numerical simulation for electron beam interaction with RF fields are given. The diode MIG is simulated numerically utilizing our code in detail. The permanent magnet system provided the maximum axial magnetic field of about 4.5 kG in the cavity region of the gyrotron. The Ka band third-harmonic complex cavity gyrotron with a permanent magnet system has been designed, constructed, and tested. A pulse output power of 147.3 kW was obtained at a beam voltage of 45 kV with beam current of 32.2 A, corresponding to an efficiency of 10.2%.

下地膜を用いずに作製したｃ軸配向Ｂａフェライト薄膜の薄層化および生成機構

The c-axis oriented Ba-ferrite thin films without underlayer were prepared, and their magnetic properties and crystal structures were investigated. Ba-ferrite thin films were deposited on fused quartz substrates, which were kept at room temperature, using rf diode magnetron sputtering apparatus. Two kinds of Ba-ferrite target disks were used; one was FeBa ratio of 6.5 and another was that of 16. The films with a thickness of 20 nm were deposited by using the target with Fe/Ba ratio of 16, and then annealed at 800°C for 5 hrs in air. They were not crystallized, but the films deposited by using the target with Fe/Ba ratio of 6.5 and then annealed at 800°C for 5 hrs in air were crystallized. Thus using target with Fe/Ba ratio of 6.5 is found to be useful for reduction of thickness. Moreover, the c-axis of Ba-ferrite films was oriented perpendicular to the film surface that was caused by the effect of { 111 } oriented Fe3O4 formed at interface between film and substrate. It was confirmed that the {111} oriented Fe3O4 was formed because of diffusion of Ba ions to the substrate.

Operation of a relativistic rising-sun magnetron with cathodes of various diameters

This paper presents results of an experimental investigation of a relativistic L-band (1.3 GHz) 10-cavity rising-sun magnetron with cathodes of various diameters. A major goal was to investigate the effect of the cathode diameter on the overall performance, mode stability and pulse shortening of this magnetron when operating at voltages of 100-500 kV and microwave peak power of P/sub /spl mu// /spl sim/ 100-700 MW. The largest levels of P/sub /spl mu// /spl sim/ 700 MW have been achieved, as expected, with cylindrical velvet cathodes. Mode structure and mode competition/switching for each cathode has been investigated in the entire range of operating magnetic fields. A cathode plasma expansion was found to be not the primary factor in a mode instability and pulse shortening of the magnetron investigated. Experimental results on effective magnetron diode gap, uniformity of electron emission, variation of the peak microwave power and microwave pulse duration with the cathode diameter and a correlation between the magnetron operating point and Buneman-Hartree curves are also presented and discussed.

Role of Nd/Ba substitution on the growth mode and on the structural properties of Nd-rich Re 1(Nd xBa 2− x)Cu 3O 7− δ (Re=Nd, Y) thin films

Thin films of the superconducting Nd 1+ x Ba 2− x Cu 3O 7− δ (NBCO) and Y 1(Nd x Ba 2− x )Cu 3O 7− δ (YNBCO) compounds have been deposited by dc magnetron sputtering and diode high pressure oxygen sputtering. Different techniques, including scanning tunneling microscopy, atomic force microscopy, X-ray diffraction and transmission electron microscopy (TEM) have been used to study the film microstructures and the surface morphology. It is shown that the Nd/Ba exchange promotes a 2D heteroepitaxial growth in the case of the NBCO films deposited on (1 0 0) SrTiO 3 substrates, with a suppression of the characteristic 3D spirals structures. On the contrary in YNBCO the Nd/Ba exchange does not provide a driving force for the suppression of screw-dislocations, since spirals or towers originated by screw and half loop dislocations are observed on the surface. TEM reveals that anti-phase boundaries are eliminated during the growth of NBCO films thanks to the Nd/Ba exchange while this mechanism is not operating in the case of YNBCO films.

Electron beam generation in a magnetron diode with metal secondary-emission cathode

The effects of electric and magnetic field intensities, the triggering-pulse droop rate, and the electrode diameter on the processes of electron beam formation and generation were studied experimentally. The results of mathematical simulation of the secondary-emission multiplication of the electron flow are presented. Tubular electron beams with a wall thickness of 1.5–2 mm, a current density of 1–70 A/cm2, and a particle energy of 5–100 keV were obtained. It was shown that several electron bunches could be obtained during a single voltage pulse.

Crossed E×B-Fields Back-Bombardment Instability and Ion Cyclotron Heating of Gas-Discharge Plasma Streams

The article present our recent results of computer simulations and theory analysis concerning of dynamics of the crossed E×B-fields back-bombardment (BKB) instability in magnetron diodes. The concept of the BKB-instability applied to show new explanation for known experimental data of an intense ion heating in accelerated plasma streams. Main features of the BKB-instability into ion diodes are following: 1) ion magnetic insulation is d0 > ri where d0 is accelerating gap across applied magnetic field B0, ri = 5V00.5/B0 is proton Larmor radius, cm; V0 – applied voltage, kV; B0 – kG; 2) EA ≠ 0 is high electric field on self or secondary emission anode electrodes; 3) main frequency oscillation of fs = fci/2 = 0.76 B0 MHz; 4) convert power efficiency of ηB = P~/P0 is up to 50%.Radial proton HF-oscillations current density of the Jir provided by the BKB-instability excites magnetohydrodynamics waves. They are propagated in the tube plasma with azimuthal velocity v∼9 ~ 107 cm/s (Miv∼92 ~ eV0) and along the B0 with the vA ~ 4×107 cm/s -Alfven velocity. Known experimental data was demonstrated a level of the HF-oscillation power which was absorbed by proton streams by ion cyclotron heating equals up to 30% total supply power of the 1 MW.Work supported by RFFI under grant 96-02-19215.

シナジー磁石と磁性材料 バリウムフェライト薄膜の低温作製に及ぼす添加物の影響

The effect of additives on low temperature preparation for barium ferrite thin films and their magnetic properties have been investigated. Bi2O3 and PbO which have low melting point were selected for additives. Barium ferrite thin films were deposited on fused quartz substrate by r.f. diode magnetron sputtering method. In order to control the composition in the deposited barium ferrite films, several sintered BaFe2O4 chips, Bi2O3 chips and PbO chips were placed on the barium ferrite target with Fe/Ba ratio of 10. The film thickness was about 2000Å. As-deposited films were post-annealed at the temperatures between 500°C and 700°C for 5 hours in air.Both Bi added barium ferrite films with Bi/Ba ratio between 2.0 and 2.3 and Pb added barium ferrite films with Pb/ Ba ratio of 3.2 or above were well crystallized by the post-annealing at 550°C for 5 hours in air. Especially, Pb added barium ferrite films with Pb/Ba ratio of 0.55 showed excellent magnetic properties, and its grains were small and uniform.

Characteristics of triode magnetron sputtering: the morphology of deposited titanium films

This paper presents a modification to conventional diode magnetron sputtering systems that results in higher ionisation rates with a consequent possibility of maintaining the discharge at lower pressures. The introduction of a grounded or positively biased grid in front of the target increases the target current substantially compared with the diode configuration. In addition, the discharge can be maintained at a lower target voltage, thus increasing the range of deposition rate. With a low-pressure discharge maintained during film deposition, the mean free path of the sputtered atoms increases. As a consequence, they reach the substrate with a high energy and, thus, a high-density film is obtained. Therefore, by using the triode magnetron configuration and setting the substrate temperature to 100 °C, it is possible to deposit a titanium film having a similar morphology to one deposited in the diode system at 400 °C. Finally, the electrode placed in front of the cathode probably produces a more homogeneous spatial distribution of electron density, resulting in a significantly higher discharge stability in the triode configuration.