Multipactor threshold sensitivity to Total Electron Emission Yield in parallel-plate waveguide and TEEY models accuracy (original) (raw)
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Analysis of Multipactor RF Breakdown Thresholds in Elliptical Waveguides
A multipactor breakdown analysis is presented for the fundamental mode of an elliptical waveguide. A 2-D geometry of the waveguide is considered, and the numerical method of Monte Carlo based on the effective-electron approach is used. Multipactor breakdown threshold prediction is performed using the enhanced counter function. The radio-frequency (RF) breakdown threshold is obtained as a function of the frequency-gap product for different values of the ellipse eccentricity. The results indicate that decreasing the ellipse eccentricity increases the RF breakdown threshold. The results are compared with those for circular and parallel-plate waveguides.
CNES – Chalmers – IAP – ONERA - XLIM activities in the domain of high RF power breakdown phenomena
EPJ Web of Conferences, 2017
Multipactor breakdown is an important potential failure mechanism in many different microwave devices working under close to vacuum conditions. Applications range from space borne RF equipment to high-power microwave generators. The basic physics involved in the multipactor phenomenon is well known for the case of two infinite pallel plates made of metal. However, most realistic RF device geometries involve inhomogeneous RF electric fields and curved field lines and sometimes also dielectric material. The purpose of this paper is to set up methodologies to determine the Multipactor threshold in such situations.
Investigating the Role of Reflected Electrons in Multipactor Breakdown
those that did not, for a range of transmit power levels, in a space-borne rectangular waveguide with TE 10 propagation mode using a developed MP prediction algorithm. Results generated indicated that, in the case were reflected electrons were properly accounted for, there were more transmit power levels with larger values of enhanced counter function (or increased electron population) than the case where consideration was not given to reflected electrons. The result also indicated that a multipactor discharge event can occur where under some current techniques multipactor is predicted not to occur.
RF Breakdown in High Vacuum Multimegawatt X-Band Structures
2004
Increasing the power handling capabilities of rf components is an important issue for the design of rf accelerators and rf sources. RF breakdown is a phenomena that limit the high power performance. A major concern is the damage that can occur in rf components from breakdown. To better understand this damage, we have studied rf breakdown in a rectangular waveguide experimentally and theoretically. The breakdown process in a waveguide is both easier to measure and simulate than breakdown in a complex geometry such as an accelerating structure. We used a particle tracking code and a Particle-In-Cell code to model the breakdown behavior. Models developed for the waveguide were applied to the breakdown in accelerating structures. RF breakdown in traveling wave and standing wave accelerating structures was simulated. We compare the experimental data with results of the simulations for the accelerating structures.
Effect of RF Parameters on Breakdown Limits in High-Vacuum X-Band Structures
2003
RF breakdown is one of the major factors determining performance of high power rf components and rf sources. RF breakdown limits working power and produces irreversible surface damage. The breakdown limit depends on the rf circuit, structure geometry, and rf frequency. It is also a function of the input power, pulse width, and surface electric and magnetic fields. In this paper we discuss multi-megawatt operation of Xband rf structures at pulse width on the order of one microsecond. These structures are used in rf systems of high gradient accelerators. Recent experiments at Stanford Linear Accelerator Center (SLAC) have explored the functional dependence of breakdown limit on input power and pulse width. The experimental data covered accelerating structures and waveguides. Another breakdown limit of accelerating structures was associated with high magnetic fields found in waveguide-to-structure couplers. To understand and quantify these limits we simulated 3D structures with the electrodynamics code Ansoft HFSS and the Particle-In-Cell code MAGIC3D. Results of these simulations together with experimental data will be discussed in this paper.
2020 IEEE 21st International Conference on Vacuum Electronics (IVEC), 2020
Vacuum electron devices (VEDs) can experience degraded performance, including complete failure, due to multipactor breakdown (MPB). This effect is tied to the production and acceleration of secondary electrons due to electron impact and coupling to the RF fields. In order to better understand the initiation of MPB with materials of interest, researchers at the University of New Mexico (UNM) are carrying out a study of the secondary electron yield (SEY) contribution from various materials used in high power VEDs. This work describes SEY data from electron bombardment in the low energy regime, from 10 eV to 1 keV, on Cu as a baseline material, - stainless steel, aluminum 6061 (Al) and Invar (Fe64/Ni36). SEY data for Cu as a function of incident beam angle is also presented. In addition, different surface cleaning treatment protocols employed in this study will be described.
Simulations of multipactor thresholds in shielded microstrip lines
Journal of Physics D: Applied Physics, 2009
A particular software 'MuSLi' has been developed and applied for simulations of the multipactor effect in shielded microstrip lines with cross-sections that are partially filled with dielectric material. The software combines an electromagnetic field solver, determining the electric field structure in the microstrip line, and a Monte Carlo algorithm, calculating the corresponding electron trajectories taking into account a spread of the electron initial velocity and different secondary emission properties of the metal and dielectric surfaces. The simulations were carried out for a number of structures of interest for communication systems, currently being discussed for application in coming space missions. The microstrip line system is shown to be strongly resistant to multipactor growth and the main reason for this is identified as the ponderomotive (or Miller) force, which governs the average electron motion in non-uniform rf fields and which tends to push the electrons out of regions with strong rf fields.
Calculations of Multipactor Growth in Rectangular Waveguides
IEEE Transactions on Plasma Science, 2019
Multipactor growth in rectangular waveguides is probed based on a kinetic approach. Unlike most studies relying on the Vaughan model, a probabilitic approach for random multiple secondary particle emissions is used. Spread in electron emission velocities, the angular dependence of secondary emission yields, and an external radio frequency (RF) driving field due to a TE10 mode, were all built in. The calculations predict the secondary emission yield for copper, probe the population growth dynamics, and obtain the susceptibility diagram. Despite a maximum field at the waveguide center from the RF excitation, maximum electron densities are predicted at locations symmetrically displaced from the center. The secondary electron yield (SEY) characteristics, its local maxima, and the role of oblique incident angles, collectively lead to multipactor finding its place at off-center locations.