Low-Secondary Electron Yield of Ferrromagnetic Materials and Magnetized Surfaces (original) (raw)
Related papers
2013
High secondary electron yield of metallic surfaces used in accelerator and also in space applications is of general concern. In addition to several well-known coating preparation techniques and microscopic or macroscopic mechanical roughness (grooves) which may significantly increase microwave losses the concept of magnetic surface roughness has been proposed recently to lower the effective secondary electron yield (SEY). In this concept a smooth and very good conducting surface with low microwave losses is maintained, but underneath this surface a large number of tiny permanent magnets are located to build a rough magnetic equipotential structure. In this paper we present and discuss measurement of the SEY and the improvement in terms of SEY for different parameter ranges.
The Secondary Electron Yield of Technical Materials and its Variation with Surface Treatments
2000
Secondary electron emission of surfaces exposed to oscillating electromagnetic field is at the origin of the multipacting effect that could severely perturb the operation of particle accelerators. This contribution tries to illustrate by measurement results, the origin of the secondary electron emission as well as the main reasons for the discrepancies between technical materials and pure metals. The variation of
Sharp reduction of the secondary electron emission yield from grooved surfaces
Journal of Applied Physics
The effect of an artificially enhanced rough surface on the secondary electron yield (SEY) was investigated both theoretically and experimentally. Analytical studies on triangular and rectangular grooved surfaces show the connection between the characteristic parameters of a given geometry to the SEY reduction. The effect of a strong magnetic field is also discussed. SEY of grooved samples have been measured and the results agree with particle simulations using a Monte Carlo approach.
Low secondary electron yield engineered surface for electron cloud mitigation
Applied Physics Letters, 2014
Surface loss probability of atomic hydrogen for different electrode cover materials investigated in H2-Ar lowpressure plasmas J. Appl. Phys. 116, 013302 (2014); 10.1063/1.4886123 X-ray photoelectron spectroscopy and secondary electron yield analysis of Al and Cu samples exposed to an accelerator environment Total secondary-electron yield of metals measured by a dynamic method Temperature dependence of the electron induced gas desorption yields on stainless steel, copper, and aluminum J.
A rapid technique for the determination of secondary electron emission yield from complex surfaces
Journal of Applied Physics, 2019
Plasma-wall interaction in the presence of secondary electron emission (SEE) can lead to a degradation and reduction in the performance of plasma devices. Materials with complex surface architectures such as velvet, fuzz, and feathered surfaces have a lower SEE yield than the same materials with a flat surface and can, therefore, be useful for plasma applications. This reduction in the SEE is due to the trapping of secondary electrons in the microcavities formed by complex surfaces. In this paper, we present a rapid method for a simultaneous comparison of the SEE yield and surface properties of materials with different surface architectures. The method uses Scanning Electron Microscopy to simultaneously evaluate the surface morphologies and SEE yield properties for a microarchitectured surface. This technique was applied to carbon velvets, and results show agreement with recent theoretical models and with the direct determination of the SEE yield from measurements of the currents of...
Influence of the Electric Field on Secondary Electron Emission Yield
AIP Conference Proceedings, 2008
We present results of the investigation of secondary electron emission from spherical amorphous carbon grains of 3 to 6 micrometers in diameter affected by a high surface field. In our experiment, we have applied a technique based on levitation of a single charged grain in the quadrupole trap. This grain was charged by an electron beam with an energy tunable up to 10 keV. During this process, the grain charge is continuously monitored. If the grain is charged by an appropriate energetic electron beam, its charge (and the corresponding surface potential and surface electric field) is set to a value when the yield of secondary emission is equal to unity (crossover point). The investigations reveal that the energy corresponding to the crossover point changes proportionally to the grain potential. This effect was attributed to an increase of the yield of secondary emission due to a large electric field at the grain surface. Moreover, the measurement of the net current on the grain induced by electrons with the energy between first and second crossover points indicates similar increase of the yield.
On the secondary electron emission phenomenon when originating from very thin layers
2017 IEEE 17th International Conference on Nanotechnology (IEEE-NANO), 2017
The secondary electron emission phenomenon lays down the principle of operation of many physical devices and processes. Although it is fairly well described in the case of irradiation of metals there is still lack of information on the secondary electron emission when originating from dielectrics. In this work we report on the secondary electron emission resulting from very thin layers. It is found that for dielectric SiO 2 layers of less than 100 nm of thickness a departure from the general behaviour occurs for incident primary electrons with energy of around 1 keV. The departure in the electron emission yield heavily depends on the layer thickness. The case of nanostructured layersdielectric matrices containing metal nanoparticles is also considered in the study.
Engineered surfaces to control secondary electron emission for multipactor suppression
2016 IEEE National Aerospace and Electronics Conference (NAECON) and Ohio Innovation Summit (OIS), 2016
A significant problem for space-based systems is multipactor-an avalanche of electrons caused by repeated secondary electron emission (SEE). The consequences of multipactor range from altering the operation of radio frequency (RF) devices to permanent device damage. Existing efforts to suppress multipactor rely heavily on limiting power levels below a multipactor threshold. 1 This research applies surface micromachining techniques to create porous surfaces to control the secondary electron yield (SEY) of a material for multipactor suppression. Surface characteristics of interest include pore aspect ratio and density. A discussion is provided on the advantage of using electroplating (vice etching) to create porous surfaces for studying the relationships between SEY and pore aspect ratio & density (i.e. porosity). Preventing multipactor through SEY reduction will allow power level restrictions to be eased, leading to more powerful and capable space-based systems.
IEEE Transactions on Plasma Science, 2000
Secondary electron emission (SEE) is one of the main parameters controlling spacecraft potential. It also plays an important role in the triggering of the multipactor phenomenon occurring in waveguides (electron avalanche in microwave electric fields). In this paper, we propose an original method adapted to low-energy SEE measurements on dielectrics and conductors (incident electron energy below 20 eV). It is based on Kelvin probe (KP) surface potential measurements after electron irradiation. It is particularly well suited to insulating materials but can also be used on metals by letting the sample potential float. We present results of SEE measurements performed on metals used in waveguides, Kapton, Teflon, and CMX cover glass. In order to avoid any experimental artifact due to the earth magnetic field and conduct accurate low-energy measurements with the KP method, the distance between the electron gun and the sample is chosen to be negligible compared to the Larmor radius.
Carbon coatings with low secondary electron yield
Vacuum, 2013
Carbon thin films for electron cloud mitigation and anti-multipacting applications have been prepared by dc magnetron sputtering in both neon and argon discharge gases and by plasma enhanced chemical vapour deposition (PECVD) using acetylene. The thin films have been characterized using Secondary Electron Yield (SEY) measurements, Scanning Electron Microscopy (SEM), Nuclear Reaction Analysis (NRA) and X-ray Photoelectron Spectroscopy (XPS). For more than 100 carbon thin films prepared by sputtering the average maximum SEY is 0.98+/-0.07 after air transfer. The density of the films is lower than the density of Highly Ordered Pyrolytic Graphite (HOPG), a fact which partially explains their lower SEY. XPS shows that magnetron sputtered samples exhibit mainly sp 2 type bonds. The intensity on the high binding energy side of C1s is found to be related to the value of the SEY. Instead the initial surface concentration of oxygen has no influence on the resulting SEY, when it is below 16%. The thin films produced by PECVD have a much higher maximum SEY of 1.49+/-0.07. Storage conditions in air, namely wrapping in aluminium foil, preserves the low SEY by more than one year. Such coatings have already been applied successfully in accelerators and multipacting test benches.