New Antenna Designs to Boost the Plasma Density in Helicon Sources

Abstract

Plasma can be generated using radio frequency (RF) electromagnetic waves for a large variety of applications, such as energy and propulsion generation. Often, the desire is to achieve higher densities for given input power and helicon sources have demonstrated a high efficiency. The design of the antenna that couples the wave plays a major role in the efficiency of generating the plasma particles. Many geometries were studied and compared, but the relationship between the antenna characteristics and the plasma production is still missing. In this article, we identify the power-law dependence between the plasma density and the Gain of an antenna. The latter is determined using numerical simulations in a vacuum, whereas the former is acquired experimentally. The power-law dependence is obtained using four different antenna elements operating under the same experimental conditions on the Polaris linear plasma device. The design a posteriori of a new inductive antenna with a modified quadrifilar helix topology, exhibits not only a higher gain but also confirms the power law. The confirmation of this law will significantly impact the future of many technologies that leverage helicon plasmas.Index Terms-Antenna design, antenna gain, helicon plasma, magnetized plasma devices, radio frequency (RF) antenna. I. INTRODUCTIONP LASMA generation in laboratories has a wide range of applications in a variety of fields like in nuclear fusion [1], space thrusters [2], and plasma processing [3]. A large number of studies are thus dedicated to the production of hot and dense plasma using electromagnetic waves. In 1997, a first review, done by Chen and Boswell [4] presented an account of the understanding of helicon waves and the experimental results. Later in 2015, Chen [5] gave another comprehensive summary of the physics of helicon discharges. In 2018, Shinohara [6] wrote an overview of the experimental results related to radio frequency (RF) sources and their applications.The first helicon plasma source was achieved in an experiment conducted by Lehane and Thoneman [7]. Later on,

Frequency reconfigurable slot antenna utilizing solid-state plasma S-PIN diodes: simulation and experimental analysis

“…Specifically, at a bias voltage of 1.7 V, the slope resistance of the dual S-PIN diodes is reduced by approximately 32.4% compared to the single S-PIN diode. This reduction in slope resistance also implies that the solid-state plasma region of the dual S-PIN diodes can achieve a higher carrier [9] Single S-PIN 100 0.9 [13] Single S-PIN 100 0.94 [15] Single S-PIN 30 0.7 This work…”

“…The foundational concept of a reconfigurable solid-state plasma antenna was originally proposed by Fathy et al [6] in 2003. This concept offers a significant level of operational flexibility and enhanced integration compared to a gas-state plasma antenna [7][8][9][10][11][12][13][14][15]. Subsequent advancements in this field have been characterized by notable contributions.…”

Effect of antenna helicity on discharge characteristics of helicon plasma under a divergent magnetic field

“…The blue core appears and extends from upstream of the discharge tube to downstream as the power is increased. The presence of blue core is often used to represent the helicon plasma discharge entering W mode [11,26,[32][33][34]. Boswell [8] suggested that the blue core mode discharge was a sign that the helicon plasma discharge mode had jumped to wave mode.…”

“…This leads to the idea that electrons are accelerated to ionization energy due to their capture by the larger field at the antenna. Chang et al [26] simulated the helicon plasma discharge coupled by a semi-helical antenna (m 1) under a uniform magnetic field to calculate the wave propagation and power deposition in the blue core. Ali et al [27] designed a modified quadrifilar helical antenna and determined the relationship between plasma characteristics and antenna topography.…”