A small inductively coupled plasma source has been developed for use in an ion thruster. A 10.1-mm-diameter thick film silver spiral antenna is fabricated on a low-temperature cofired ceramic with a 35- $muhbox{m}$ dielectric over the antenna. The antenna has been able to sustain an argon plasma over a frequency range from 448 to 1020 MHz with pressures ranging from 50 mtorr to 1.75 torr. Plasma start powers ranged from 3 to 50 W with minimum sustain powers down to 0.1 W. Antenna electric field measurements have been made in air and compared with simulation of the antenna field using COMSOL. These results show that the antenna pattern is dominated by the standing wave pattern of the spiral antenna. Simulations of the RF power density versus frequency compare well with the plasma start power variation except for a large start power peak between 600 and 700 MHz
This work focuses on the fabrication and assembly of cylindrical plasma containment tubes using DuPont\u27s 951 low temperature co-fired ceramics (LTCC) for use in miniature electrostatic thrusters. The tube is used to contain argon plasma, which is generated by a spiral inductively coupled plasma antenna, which is also fabricated in LTCC. The tube also interfaces with two electrically biased grids on the opposite end, which accelerate the plasma out of the tube. These interfaces are highly dependent on the dimensions and tolerances of the containment tube. The development of the fabrication process will be presented for the incorporation of the tubes and grids onto the base as a single structure. This includes constructing the antenna base, shaping the “rolled” LTCC containment tube using a jig and isostatic press, and integrating the tube and antenna base during the firing. Following the fabrication, measurements will be taken to determine tube circularity and hermeticity of the seal at the interface between the tube and the antenna base. The results will be presented and characterized to evaluate the effectiveness of the structure as well as the documentation of the development of a rolled LTCC tube structure integrated with a planar LTCC antenna base
A miniature electrostatic thruster is being developed in Low Temperature Co-fired Ceramic (LTCC) at Boise State University. The thruster is composed of an antenna to create the plasma, a cylinder to contain the plasma, and grids to extract the plasma beam at high velocity. In this work, the development of the inductively coupled plasma (ICP) antenna in LTCC will be presented. This antenna is fabricated using DuPont 951 LTCC tape. A Direct Write dispenser is used to apply silver paste for the spiral ICP antenna. Using LTCC allows for the antenna to be embedded in the device under a thin sheet of LTCC dielectric, which protects the antenna from ion back bombardment during operation. This thin sheet is the seventh layer of the total device, with the ICP antenna one layer below the top. The design of the antenna is based on the research done by J. Hopwood. This article discusses the fabrication and performance of the ICP antennas in LTCC. These ICP antennas are operated at pressures from 10 mTorr to 1 Torr with radio frequencies (RF) of 500 MHz to 1 GHz to inductively couple with low-pressure argon to produce plasma. The performance of the antennas will be verified with data showing the start and stop power of the plasma at various pressures and an electric field map of the RF field above the antenna
With the size reduction of satellites, the need for miniaturized propulsion systems is increasing. This has led to research funding for the miniaturization of chemical and electric propulsion by NASA and the Air Force Office of Scientific Research (AFOSR). Miniaturized electric propulsion research has been an active area of interest recently. Electric propulsion systems are interesting candidates for miniaturization due to efficiency and the reduction in onboard propellant and the ability to apply existing techniques in electronic fabrication. A miniature electrostatic thruster is being developed in LTCC at Boise State University. The thruster is composed of an antenna to create the plasma, a cylinder to contain the plasma and grids to extract the plasma beam at high velocity. In this work, the development of the inductively coupled plasma (ICP) antenna in LTCC will be presented. This antenna is fabricated using DuPont's 951 Low Temperature Co-fired Ceramic (LTCC). A Direct Write is used to apply silver paste for the spiral ICP antenna. Using LTCC allows for the antenna to be embedded in the device under a thin sheet of LTCC dielectric, which protects the antenna from ion back bombardment during operation. This thin sheet is the seventh layer of the total device, with the ICP antenna one layer below the top. The design of the antenna is based on the research done by J. Hopwood. This paper discusses the fabrication and performance of the ICP antennas in LTCC. These ICP antennas are operated at pressures from 10 mTorr to 1 Torr with radio frequencies (RF) of 500 MHz to 1 GHz to inductively couple with low pressure argon to produce plasma. The performance of the antennas will be verified with data showing the start and stop power of the plasma at various pressures and an electric field map of the RF field above the antenna.
Scaling down electric propulsion systems is of interest for the future development of propulsion systems for micro-and nano-satellites. Because of the low mass of nano-satellites, only a small amount of thrust, on the order of several hundred µN, is needed for tasks such as attitude control.An Inductively Coupled Plasma source (ICP), fabricated in Low Temperature Co-fired Ceramic (LTCC), has been developed. The ICP is now being integrated into a miniature ion thruster, with a diameter of approximately 2cm; the thruster body is also made of LTCC.The design of the antenna for the ICP has been optimized to generate the maximum electric field at a peak frequency in the range of 450MHz-1GHz. The antenna design was simulated using COMSOL Multiphysics modeling software, and the antenna field pattern has been verified experimentally.Plasma generated by the ICP will be characterized by a Langmuir probe at several frequencies in order to determine the optimum frequency that will create the densest plasma with minimal rf power. Measurements with the Langmuir probe will be performed in three configurations: the ICP by itself, the ICP with a 2cm diameter LTCC cylindrical tube surrounding the ICP antenna, and finally the ICP with the LTCC tube and two rings of magnets alternating in polarity to create a magnetic cusp.A two-gridded electrical system will be employed in order to extract ions from the thruster and create thrust. The screen grid, the closest grid to the plasma, will be biased at 1000V while the second grid, the accelerator grid, will be biased to -200V. Ions will accelerate through this electric potential. Beam divergence and thrust will be measured with a collector plate at varying distances from the thruster. Three collector plates will be used: a radial pad layout, an azimuthal pad layout, and a single pad layout in order to measure the radial pattern, azimuthal pattern, and total thrust, respectively. The simulated and experimental results will be presented. ________________________________ *
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