The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare metal. Close to this layered surface, the power spectral density of the electric field varies with the inverse fourth power of the distance to the surface, rather than with the inverse square, as it would above a bare metal surface. Furthermore, compared to a clean metal, where the noise spectrum does not vary with frequency (in the radio-wave and microwave bands), the dielectric layer can generate electricfield noise which scales in inverse proportion to the frequency. For various realistic scenarios, the noise levels predicted from this model are comparable to those observed in trapped-ion experiments. Thus, these findings are of particular importance for the understanding and mitigation of unwanted heating and decoherence in miniaturized ion traps.
The effects of an electric field shield on the electric field noise and neutralizing current of a corona discharge air ionizer were investigated as a means to prevent soft errors during quality control inspections. The neutralizing current and noise voltage were measured for shielded and nonshielded air ionizers using a charged plate monitor. The use of an electric field shield decreased both the neutralizing current and the noise voltage. Therefore, neutralizing current to noise voltage ratio was calculated to evaluate the effect of the shield on the neutralization performance, and this ratio was several times higher for the shielded air ionizer than for the nonshielded air ionizer. (c) 2016 Institute of electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
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