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Paul C. Nordine, Dennis Merkley, Jeffrey Sickel, Steve Finkleman, Rainer Telle, Arno Kaiser, and Robert Prieler.
Copyright (2012) American Institute of Physics.
This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
The article appeared in Rev. Sci. Instrum. 83, 125107 (2012) and may be found at doi: 10.1063/1.4770125.
Abstract:
A new aero-acoustic levitation instrument (AAL) has been installed at the Institute for Mineral Engineering at RWTH University in Aachen, Germany. The AAL employs acoustically stabilized gas jet levitation with laser-beam heating and melting to create a contact-free containerless environment for high temperature materials research. Contamination-free study of liquids is possible at temperatures in excess of 3000 °C and of undercooled liquids at temperatures far below the melting point. Digital control technology advances the art of containerless experiments to obtain long-term levitation stability, allowing new experiments in extreme temperature materials research and to study operation of the levitation instrument itself. Experiments with liquid Al2O3 at temperatures more than 3200 °C, 1200 °C above the melting point, and with liquid Y3Al5O12 far below the melting point are reported. Fast pyrometry and video recording instruments yield crystallization rates in undercooled liquid Al2O3 as a function of temperature. Levitation of dense liquid HfO2 at temperatures above 2900 °C is demonstrated. Capabilities are described for resonant frequency matching in the three-axis acoustic positioning system, acoustic control of sample spin, and position control of standing wave nodes to stabilize levitation under changing experimental conditions. Further development and application of the levitation technology is discussed based on the results of experiments and modeling of instrument operations.
Jeffrey Sickel. In: Proceedings of the 4th International Workshop on Plan 9 (IWP9), 21-23 Oct. 2009, Athens, Georgia.
Abstract:
The Styx (9p) protocol has been well documented for use in various distributed systems. Demonstrations have proven that it works for communication with embedded devices. This paper presents an implementation of 9p for the 16-bit dsPIC33 family of digital signal controllers. It is used to collaborate multiple distributed nodes to achieve stable aero-acoustic levitation of a sample by tuning sound pressure levels and managing spin control.
Jeffrey Sickel and Paul Nordine. In: Proceedings of the 5th International Workshop on Plan 9 (IWP9), 11-13 Oct. 2010, Seattle, Washington.
Abstract
We describe a digital technique for tracking the resonant frequencies of
piezoelectric transducers used to drive an aero-acoustic levitator.
Real-time sampling of the voltage and current phase difference is used in a
low-priority feedback loop to control drift and stabilization.
The implementation leverages 9p on embedded 16-bit dsPIC33F digital signal
controllers. Data collection and processing are performed with various 9p
clients. This paper describes the use of 9p and Inferno to track, adjust, and
optimize output frequency and sound pressure levels on the instrument.
Jeffrey Sickel. In: Proceedings of the 6th International Workshop on Plan 9 (IWP9), 20-21 Oct. 2011, Madrid, Spain.