Electromagnetic levitator (MSL-EML)

The MSL-EML electromagnetic levitator facility is joint development of ESA and DLR and is aimed for containerless materials processing in space. The MSL-EML will be accommodated in the European Columbus Laboratory on the ISS.

MSL-EML is a multi-user facility that provides containerless melting and solidification of electrically conductive, spherical samples, under ultra-high vacuum and/or high gas purity conditions. Heating and positioning of the sample is achieved by electromagnetic fields generated by a coil system.

The MSL-EML will support research in the field of meta-stable states and phases and in the field of measurement of high-accuracy thermophysical properties of liquid metallic alloys at high temperatures. The former field covers for instance investigations of nucleation and solidification kinetics in undercooled melts and the microstructure formation.

Thermophysical properties of high temperature (and highly reactive) melts to be measured in MSL-EML include surface tension, viscosity, melting range, fraction solid, specific heat, heat of fusion, mass density and thermal expansion, together with thermal transport properties such as the total hemispherical emissivity and effective thermal conductivity.

In addition, electrical conductivity and to some extent magnetic susceptibility can be measured. Research on thermo-physical properties is highly oriented to applications where reliable data for high temperature melts are required for accurate modelling of industrial processes and where these are difficult or impossible to be obtained on ground, in particular for reactive melts.

The long-term and multiple access research conditions provided by the ISS will allow systematic study of all these phenomena to a degree that has previously not been possible.

The MSL-EML will be available as from 2011.

Experiment objectives that will be supported by the MSL-EML facility are:

  1. Undercooling and solidification speeds by measurement of undercooling temperature and solidification velocity with high-speed video camera. Triggering of solidification by touching the undercooled sample with a nucleation trigger needle will be available.

  2. Thermophysical Properties such as:
    • Heat Capacity, effective thermal conductivity, enthalpies, solid fraction
    • By modulating the heating input power into sample and measure the response of
    • sample temperature and measuring the electrical power loss to the sample
    • Surface tension and viscosity by inducing surface oscillations in the sample by pulsing or modulating the heating field and observing (through surface oscillation) frequencies and decays by video camera
    • Thermal expansion by measuring sample size with video cameras using subpixel resolution Techniques
    • Electrical conductivity by measuring electrical data of the levitation system and optionally additional electrical diagnostic circuits to detect the changes of the coupling between the RF magnetic fields with sample temperature

The system will support the performance of multiple melt cycles per sample and the systematic investigation of different experiment objectives during the same melt cycle.

The main scientific relevant specifications are as following:

The MSL-EML facility will allow the processing of spherical samples of 5-8 mm diameter up to a temperature of about 2000 °C. The samples will be processed automatically, however telescience is also available.

The samples can be processed either under high vacuum or inert gas atmosphere. A mixture of gases will also be supported as well as sample cooling by forced gas convection.

In terms of diagnostic means the MSL-EML will offer a pyrometer with a measurement spot < 2 mm and high accuracy in the range of 600-2000 °C. In addition a radial high-speed camera with 200 Hz frame rate and an axial camera are available.

The nominal field of view of 10 x 10 mm will be adjustable to other field sizes.

A backlight illumination system will be available and thermal monitoring will be possible for sample temperatures above 800 °C by the camera systems.

Power oscillations to perform surface tension and viscosity measurements are possible in the 10 Hz to 50 Hz frequency range.

TEMPUS, TEXUS

To prepare for the utilisation of MSL-EML, ESA and DLR co-sponsor the utilisation of the TEMPUS facility on parabolic flights usually once a year, offering 20 seconds of microgravity time per parabola.

Precursor experiments using a sounding rocket version of the EML (TEXUS-EML) are performed on a regular basis once a year with two samples allowing about 180 seconds of microgravity time per sample.

Last update: 13 May 2009

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