The Secondary Electron Yield of Technical Materials and its Variation with Surface Treatments (original) (raw)
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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.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1991
Experiments have been performed to study the influence of projectile molecular effects on the production of secondary electrons in the MeV/amu energy regime. Secondary-electron yields from Au, Ta and Al,O, surfaces were measured using charged-particle projectiles provided by Van de Graaff accelerators (H+ at 1.5-6 MeV, H: at 2-6 MeV, H; at 3-6 MeV, 3Hef at 13-22 MeV, 3He2+ at 13-33 MeV, 4He+ at 18-22 MeV, and 4He2+ at 18-33 MeV) and scanning electron microscopes (electrons at 0.8-30 keV). For low projectile velocities, the total electron yield due to a composite projectile is less than the sum of the yields of the individual components of that projectile. This "molecular effect" is attributed to interference effects between the individual components of the projectile which lessen each component's ability to produce secondary electrons. As the projectile velocity is increased, these interference effects are reduced and the projectile as a whole becomes more effective in producing secondary electrons. Secondary electrons produced by backscattered electrons were also studied and found to constitute 60-808 of the total number of secondary electrons emitted from Au and Ta and-40% of those emitted from Al,O,. These results are interpreted in terms of existing theories of secondary-electron emission. Ongoing computer simulations are contributing to an understanding of the particle dynamics of the secondary-electron emission process for composite projectiles and are showing qualitative agreement with experiment.
The Dose Effect in Secondary Electron Emission
IEEE Transactions on Plasma Science, 2009
In this paper, total incident electron dose as an inherent parameter in secondary electron emission is experimentally demonstrated. A completely automated experimental setup allows for measuring of secondary electron yield (SEY) as a function of beam energy, angle of incidence of primary electrons, electron dose, and time. SEY data are presented for copper, plasmasprayed boron carbide, and titanium nitride samples with principal focus on dose dependence. Experiments were conducted in the low-energy range (5-1000 eV) and direct-current regime. Experimental results have been compared with formulas in literature, and good agreement was observed. Modified empirical formulas incorporating the dose effect have also been proposed. Index Terms-Dose effect, high-power microwaves (HPMs), secondary electron emission (SEE), secondary electron yield (SEY).
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.
Physical Review Letters, 2012
We performed a combined secondary electron yield (SEY) and x-ray photoelectron spectroscopy study as a function of the electron dose and energy on a Cu technical surface representative of the LHC accelerator walls. The electron bombardment is accompanied by a clear chemical modification, indicating an increased graphitization as the SEY decreases. The decrease in the SEY is also found to depend significantly on the kinetic energy of the primary electrons. When low-energy primary electrons are employed (E 20 eV), the reduction of the SEY is slower and smaller in magnitude than when higherenergy electrons are used. Consequences of this observation are discussed mainly for their relevance on the commissioning scenario for the LHC in operation at CERN (Geneva), but are expected to be of interest for other research fields.
Secondary Electron Emission from Thin Aluminium Foils Produced by High Energy Electron Beams
Problems of Atomic Science and Technology
The description of the experimental equipment and technique for measuring the secondary emission of elec-trons (SEE) with application of accelerated electrons at the linear accelerator of the IHEPNP NSC KIPT with ener-gies up to 30 MeV and a standard secondary emission monitor [1] are presented. Experimental data of secondary electron emission yields from thin aluminum targets (8 and 50 μm) for primary electron beam energies of 16 and 25 MeV have been experimentally measured. The analysis of the experimental data and their comparison with the theory are carried out. It is shown that the proposed technique for measuring the yields of secondary electron emis-sion is useful and applied for study of low-energy and δ-electrons yields from thin foils, as well as to research the effect of the density effect depending on the energy of the primary electron beam.
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.
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...