A microwave interferometer for small and tenuous plasma density measurements

Tudisco, O.; Fabris, Andrea Lucca; Falcetta, C.; Accatino, L.; Angelis, R. De; Manente, Marco; Ferri, F.; Florean, M.; Neri, C.; Mazzotta, C.; Pavarin, Daniele; Pollastrone, Fabio; Rocchi, G.; Selmo, A.; Tasinato, L.; Trezzolani, Fabio; Tuccillo, A. A.

doi:10.1063/1.4797470

Cited by 42 publications

(20 citation statements)

References 15 publications

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“…The plasma discharges have been characterised in terms of plasma density. With the aim of mapping the plasma density within the discharges, we relied on a microwave interferometer, which is capable of plasma density measurements regardless of the gas type [24]. The instrument is movable along the axis of the discharge and measures the average electron density in a plasma slab extending to the entire diameter of the source (see Fig.…”

Section: Plasma Density Measurementmentioning

confidence: 99%

Beam‐forming capabilities of a plasma circular reflector antenna

Melazzi¹,

Carlo

Trezzolani³

et al. 2018

IET Microwaves, Antennas & Propagation

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A gaseous plasma antenna array (PAA) is an aggregate of plasma discharges and possibly conventional metallic radiating elements, and it constitutes a promising alternative to metallic antennas for applications in which fast reconfiguration of radiation pattern, and gain is desired; such properties can be achieved by exploiting the electronic switch on/off condition of plasma discharges, and tuning of the plasma parameters. Here, the authors present a reconfigurable PAA that features a central metallic half‐wavelength dipole working around 1.45 GHz, surrounded by a planar circular lattice of cylindrical plasma discharges. Customised plasma discharges have been realised, and filled with argon gas at 2 mbar so as to have a complete control on the plasma discharge properties (e.g. plasma frequency, collisional frequency). The magnitude of the reflection coefficient, and the gain pattern on the H‐plane have been investigated numerically and experimentally; numerical and experimental results exhibit a good agreement and show that the central intrinsically omnidirectional antenna can provide simple beamforming capabilities upon turning on a subset of plasma discharges; as these plasma discharges are turned on, the authors have observed a maximum gain of ∼5 dBi, a half‐power beam width of 80∘, and an angular steering resolution of ∼15∘.

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Section: Plasma Density Measurementmentioning

confidence: 99%

Beam‐forming capabilities of a plasma circular reflector antenna

Melazzi¹,

Carlo

Trezzolani³

et al. 2018

IET Microwaves, Antennas & Propagation

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“…To estimate the actual plasma density distribution within the plasma discharge, we have relied on a microwave interferometer [11], which is capable of plasma density measurements regardless of the gas type; specifically, the plasma density value is related to the phase shift produced on a microwave signal travelling through the plasma. The instrument works in the 10 16 ÷ 7 · 10 19 m −3 range of plasma density values, is movable along the plasma source, and measures density in a plasma slab that is extended across the diameter of the source (see Figure 6).…”

Section: The Experimental Setup Of the Plasma Directormentioning

confidence: 99%

A Reconfigurable Metal-Plasma Yagi-Uda Antenna for Microwave Applications

Mansutti¹,

Melazzi²,

Capobianco³

2017

Adv. sci. technol. eng. syst. j.

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This paper is an extension of the work originally presented at the European (CST Microwave Studio) how it is possible to achieve reconfigurability with respect to the gain by turning on/off the plasma discharges. However the model that was used to represent the plasma discharges was quite ideal, so one comment that was provided questioned the actual possibility of achieving reconfigurability in a real system. Consequently we performed extensive measurements of different plasma discharges and thanks to the collected data, we noticed some important differences between the full-wave numerical model of the plasma that we used in the conference paper and the actual plasma discharges that were generated in the experimental setup: the dielectric vessel and the metallic electrodes used respectively to confine and generate the plasma have an influence on the radiation pattern of the antenna and so they must be included in the design procedure; the cylindrical plasma discharge is much easier to realize when the cylinder diameter is at least 3mm; and finally the collision frequency of the plasma in realistic cases is pretty higher than the one adopted in our previous work. Therefore this work presents a feasibility study of a more detailed and realistic model of our antenna with respect to the plasma discharges. We will show that reconfigurability can still be achieved through a proper design of the overall antenna, thus paving the way to an actual realization of the proposed reconfigurable Yagi-Uda.

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“…The microwave interferometer [7] operates with a 75 GHz carrier modulated at 100 MHz, which is split in two separate signals: through opportune waveguide circuits one is driven through the plasma source, crossing it radially, while the other follows a reference path inside the instrument. The phase difference between the two signals depends on the plasma density according to Eq.…”

Section: B Microwave Interferometermentioning

confidence: 99%

Integrated Design Tools for RF Antennas for Helicon Plasma Thrusters

Trezzolani¹,

Selmo²,

Melazzi³

et al. 2014

50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference

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In this communication we report on a combined experimental-numerical activity that was conducted to assess the antenna-plasma interaction within a Helicon plasma source for space thrusters. The experiment is based on a versatile, re-configurable set-up which allows testing multiple thruster configurations under different operating conditions, featuring a high-efficiency RF antenna. The numerical results were obtained by means of various simulation tools for both RF circuit and antenna-plasma interface analysis; these tools were validated against experimental data. The results helped to improve our understanding of antenna-plasma coupling and the assessment/prediction of the RF system performance. Nomenclature RF= Radio Frequency HPT = Helicon Plasma Thruster RPA = Retarding Potential Analyzer IEDF = Ion Energy Distribution Function DAQ = Data AcQuisiton Pp = Active power coupled to the plasma Zp = Plasma impedance Rp = Plasma resistance Xp = Plasma reactance ηa = Antenna efficiency _______________________________________________________________________________________

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A microwave interferometer for small and tenuous plasma density measurements

Cited by 42 publications

References 15 publications

Beam‐forming capabilities of a plasma circular reflector antenna

Beam‐forming capabilities of a plasma circular reflector antenna

A Reconfigurable Metal-Plasma Yagi-Uda Antenna for Microwave Applications

Integrated Design Tools for RF Antennas for Helicon Plasma Thrusters

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