Influence of Surface Roughness on Secondary Electron Emission and Electron Backscattering from Metal Surface

Nishimura, Kenji; Itotani, Takayuki; Ohya, Kaoru

doi:10.1143/jjap.33.4727

Cited by 24 publications

(18 citation statements)

References 14 publications

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“…A maximum of the SEY δ max ≈ 2 around 300 eV is typically found for flat copper [33], and the only partial coverage of the surface treated in Ar induces an intermediate SEY reduction (δ max ≈ 1.3) with a moderate shift of the peak to a higher energy at around 500 eV. For the samples treated in air or N 2 , the more complete nanoparticle coverage allows for a much more efficient SEY reduction, with the peak potentially being shifted to energies above our maximum experimental value [34].…”

Section: Discussionmentioning

confidence: 48%

Optimization of the secondary electron yield of laser-structured copper surfaces at room and cryogenic temperature

Calatroni

Valdivieso

Fontenla

et al. 2020

Phys. Rev. Accel. Beams

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Electron cloud (e-cloud) mitigation is an essential requirement for proton circular accelerators in order to guarantee beam stability at a high intensity and limit the heat load on cryogenic sections. Laser-engineered surface structuring is considered a credible process to reduce the secondary electron yield (SEY) of the surfaces facing the beam, thus suppressing the e-cloud phenomenon within the high luminosity upgrade of the LHC collider at CERN (HL-LHC). In this study, the SEY of Cu samples with different oxidation states, obtained either through laser treatment in air or in different gas atmospheres or via thermal annealing, has been measured at room and cryogenic temperatures and correlated with the surface composition measured by x-ray photoelectron spectroscopy. It was observed that samples treated in nitrogen display the lowest and more stable SEY values, correlated with the lower surface oxidation. In addition, the surface oxide layer of air-treated samples charges upon electron exposure at a low temperature, leading to fluctuations in the SEY.

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Section: Discussionmentioning

confidence: 48%

Optimization of the secondary electron yield of laser-structured copper surfaces at room and cryogenic temperature

Calatroni

Valdivieso

Fontenla

et al. 2020

Phys. Rev. Accel. Beams

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“…In contrast, surface structures with curvature radii from nanometers to sub-microns may have a strong effect on SEE. It is also reasonable to mention that the SEE yield from the surface with distributed structures of low concentration is proportional to the concentration of the structures [29,30] and greater than the SEE yield from the smooth surface as long as 0.01 a/L 1, here L is a distance between structural elements [19].…”

Section: Discussionmentioning

confidence: 99%

“…when the distance between structural elements is much larger than their size. This excludes the effect of re-entrance of emitted electrons into another part of the surface since the probability of this process becomes very small [19]. To describe SEE due to isotropic incidence of primary electrons e − p of energy E 0 to the objects with varying surface curvature k we generalize a commonly used expression [3,6,11] for the electron yield as…”

Section: Modelmentioning

confidence: 99%

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Secondary electron emission from surfaces with small structure

et al. 2015

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It is found that for objects possessing small surface structures with differing radii of curvature the secondary electron emission (SEE) yield may be significantly higher than for objects with smooth surfaces of the same material. The effect is highly pronounced for surface structures of nanometer scale, often providing a more than 100% increase of the SEE yield. The results also show that the SEE yield from surfaces with structure does not show an universal dependence on the energy of the primary, incident electrons as it is found for flat surfaces in experiments. We derive conditions for the applicability of the conventional formulation of SEE using the simplifying assumption of universal dependence. Our analysis provides a basis for studying low-energy electron emission from nano structured surfaces under a penetrating electron beam important in many technological applications.

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“…The effect of surface roughness is simulated by [27], where it is to see that the SEY and the backscattering coefficient varies according to the height and width of the roughness. …”

Section: Influence Of the Surface Roughness On The Seymentioning

confidence: 99%

Secondary electron yield on cryogenic surfaces as a function of physisorbed gases

Kuzucan¹,

Neupert²,

Taborelli³

et al. 2012

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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In LHC the electron cloud induced by photoelectrons, gas ionization and secondary electrons emitted from the beam pipe walls could be a limitation of the performance. The electron cloud induce heat load on the cryogenic system, cause pressure rise, emittance growth and beam instabilities, which in the end will limit the beam"s lifetime. Beam-induced multipacting, which can arise through oscillatory motion of photoelectrons and low-energy secondary electrons bouncing back and forth between opposite walls of the vacuum chamber during successive passage of proton bunches, represent therefore a potential problem for the machine.The secondary electron yield (SEY) is one of the key parameters for the electron cloud build up and multipacting phenomenon. An electron cloud occurs if the metal surface secondary electron yield is high enough for electron multiplication. This parameter has been extensively studied on room temperature samples but uncertainties remain for samples at cryogenic temperature. Indeed, at low surface temperature SEY is strongly dependent on the nature of the physisorbed gases and on the surface coverage.In this work the secondary electron yield (SEY) at cryogenic temperatures has been measured and the results are presented. Of particular interest is the variation of the SEY with the gas coverage as most gases especially CO, CO 2 , and CH 4 in case of LHC condense on the cryogenic parts of the machine. In addition to these gases measurements have been performed with N 2, because of its importance as calibration gas for most of the pressure gauges and pumps. Also measurements with Kr have been done, to compare the results with existing works. In order to acquire a better understanding about the behaviour of SEY as a function of different gas coverage, measurements of work function have been made. The measurements of the SEY at cryogenic surfaces require a UHV system with a sample holder which can be cooled down to cryogenic temperatures, a source of primary electrons and detection of sample current and secondary electron current. In addition a gas injection system is necessary to produce variable coverage with different gases. In the present system the sample (Cu, Al, electro-polished Cu, Nb and C) was cooled down to 4.7K, irradiated with an electron gun and currents were measured on the sample and on a collector electrode. Work function was measured with a Kelvin Probe. KURZFASSUNG

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Influence of Surface Roughness on Secondary Electron Emission and Electron Backscattering from Metal Surface

Cited by 24 publications

References 14 publications

Optimization of the secondary electron yield of laser-structured copper surfaces at room and cryogenic temperature

Optimization of the secondary electron yield of laser-structured copper surfaces at room and cryogenic temperature

Secondary electron emission from surfaces with small structure

Secondary electron yield on cryogenic surfaces as a function of physisorbed gases

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