Surface corrugation for broadband matching of windows in powerful microwave generators

Petelin, M. I.; Kasparek, W.

doi:10.1080/00207219108925531

Cited by 14 publications

(7 citation statements)

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“…The final shape of the lens has been defined in an optimization process with the full-wave code IPF-FDMC [4,5]. Grooves on both sides of the lens minimize microwave reflection [6]. The phased array antenna is installed such that its angle variation is in toroidal direction.…”

Section: Microwave Heating Hardwarementioning

confidence: 99%

Schemes of microwave heating of overdense plasmas in the stellarator TJ-K

Köhn

Birkenmeier

Chusov

et al. 2012

Plasma Phys. Control. Fusion

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Abstract. Microwave heating of overdense low-temperature plasmas, whose density exceeds the cutoff density of the injected microwave, is described for the stellarator TJ-K. Three different methods featuring each their own characteristics are briefly presented. It is shown that TJ-K allows both fusion relevant scenarios like heating by electron Bernstein waves and fundamental wave-plasma interactions like parametric decay instabilities to be investigated.

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Section: Microwave Heating Hardwarementioning

confidence: 99%

Schemes of microwave heating of overdense plasmas in the stellarator TJ-K

Köhn

Birkenmeier

Chusov

et al. 2012

Plasma Phys. Control. Fusion

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“…The rectangular fins may have triangular transitions at both ends or they can be made entirely triangular instead or rectangular. 28,29 This provides a gradual transition from the refractive index of air to the refractive index of HDPE. The aspect ratio of the grooves can be optimized such that the thickness of the grooved section is (2n + 1) × λ/4.…”

Section: Discussionmentioning

confidence: 99%

Polarizer design for millimeter-wave plasma diagnostics

Leipold

Salewski

Jacobsen

et al. 2013

Review of Scientific Instruments

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Radiation from magnetized plasmas is in general elliptically polarized. In order to convert the elliptical polarization to linear polarization, mirrors with grooved surfaces are currently employed in our collective Thomson scattering diagnostic at ASDEX Upgrade. If these mirrors can be substituted by birefringent windows, the microwave receivers can be designed to be more compact at lower cost. Sapphire windows (a-cut) as well as grooved high density polyethylene windows can serve this purpose. The sapphire window can be designed such that the calculated transmission of the wave energy is better than 99%, and that of the high density polyethylene can be better than 97%.

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“…One can estimate the parameters of the hollows required for the bleaching effect on the basis of the approach developed in [3][4][5]. In accordance with that approach, the surface layer with hollows should have the effective dielectric permittivity ε eff = √ ε and the thickness d = λ eff /4, where λ eff = 2π/(k √ ε eff ).…”

mentioning

confidence: 99%

“…Suppression of this reflection, i.e., matching of dielectrics, is of interest for many engineering applications, e.g., bleaching of optical instruments and windows in high-power vacuum devices, etc. A frequently used method of the matching is the use of quarter-wave layers [2][3][4][5]. From [3][4][5], it is known that the matching is possible if the dielectric boundary is corrugated so that the corrugation period d λ d , where λ d is the wavelength in the dielectric.…”

mentioning

confidence: 99%

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A possibility of bleaching of dielectric boundaries for a normally incident wave independently of its polarization

Vlasov

Koposova

2009

Radiophys Quantum El

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We study the possibility of bleaching of a dielectric boundary using part-through holes (hollows). The parameters of the hollows are determined on the basis of the well-known theoretical approach, according to which the bleaching effect is possible only if the thickness of the matching layer on the dielectric surface is equal to one-fourth of the wavelength. Using this concept and solving approximately the electromagnetic-field equations, we estimate the parameters of the hollows, such as their diameter and depth, which are necessary for the bleaching effect.It is known [1, 2] that when a plane electromagnetic wave is incident on an interface between dielectrics, its reflection occurs. Suppression of this reflection, i.e., matching of dielectrics, is of interest for many engineering applications, e.g., bleaching of optical instruments and windows in high-power vacuum devices, etc. A frequently used method of the matching is the use of quarter-wave layers [2][3][4][5]. From [3][4][5], it is known that the matching is possible if the dielectric boundary is corrugated so that the corrugation period d λ d , where λ d is the wavelength in the dielectric. However, this method has some drawbacks. The degree of bleaching by using a one-dimensional corrugation having a simple form turns out to be sensitive to the polarization of the incident wave. In the case of normal incidence of an E wave (the electric field E of the incident wave is parallel to the corrugation generatrix), bleaching of the boundary requires narrow dielectric ridges with high permittivity. Boundary bleaching for the incidence of an H wave (the magnetic field H of the incident wave is parallel to the corrugation generatrix) requires wide ridges. In the case of more intricate profiles and deeper corrugations, this drawback is eliminated at the cost of more complicated machining of the surface.

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Surface corrugation for broadband matching of windows in powerful microwave generators

Cited by 14 publications

References 1 publication

Schemes of microwave heating of overdense plasmas in the stellarator TJ-K

Schemes of microwave heating of overdense plasmas in the stellarator TJ-K

Polarizer design for millimeter-wave plasma diagnostics

A possibility of bleaching of dielectric boundaries for a normally incident wave independently of its polarization

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