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Tsukizaki R.,Japan Aerospace Exploration Agency | Ise T.,University of Tokyo | Koizumi H.,University of Tokyo | Togo H.,Nippon Telegraph and Telephone | And 5 more authors.
Journal of Propulsion and Power | Year: 2014

Two optical fiber measurement techniques are used in this paper to reveal the physical mechanism of the enhancement of the thrust force of the μ10 electron cyclotron resonance ion thruster. The beam current of the μ10 thruster was increased in previous studies by changing the propellant injection method. In this study, to observe the difference in plasma distributions, optical fiber probes were inserted into the thruster under beam acceleration. The first measurement was laser absorption spectroscopy. By traversing the optical fiber, the number densities of Xe I5p5(2P0 3/2)6s [3/2]2 0 1 were obtained along the center axis. The second measurement was an electric-optic element probe measurement conducted to measure the intensities of the microwave electric field. Both measurements suggest that there is plasma in the waveguide in the conventional model of the thruster. This phenomenon is possibly caused by the leakage of electrons from the electron cyclotron resonance region to the waveguide. As a result, this paper concludes that the suppression of plasma in the waveguide is a very important measure to improve the performance of microwave thrusters. Copyright © 2014 by the American Institute of Aeronautics and Astronautics, Inc.

Shimamura T.,Microsystem Integration Laboratories | Morimura H.,Microsystem Integration Laboratories | Shimoyama N.,Microsystem Integration Laboratories | Sakata T.,Microsystem Integration Laboratories | And 3 more authors.
IEEE Sensors Journal | Year: 2012

This paper describes techniques for an impedance-sensing circuit integrated into a capacitive fingerprint sensor to prevent spoofing with a fake finger. We have reported a sensor chip with an embedded impedance-sensing function. We proposed an impedance-sensing circuit that features current-to-voltage conversion using a unity gain buffer. Here, the design of the sensing circuit is discussed. The detectable impedance range and the sensitivity are analyzed within the impedance range for various human fingers. A test chip with the proposed circuit was fabricated using 0.5-μm CMOS/sensor processes. The results confirm that the difference in impedance between a real finger and a fake finger is detected without any degradation of the original characteristics of the fingerprint sensor chip. © 2012 IEEE.

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