The electromagnetic levitator (EML) is a multi-user facility onboard the ISS, which was installed in 2014 by astronaut Alexander Gerst. In this facility a conductive sample is placed in a coil and processed containerless, heating and positioning is performed by two independent fields. This enables the scientists to process the sample without contact to a crucible and with low magnetic field strengths compared to ground-based levitation.
EML is located in the European drawer rack in the Columbus module.
The EML facility is used for the measurement of thermophysical properties of liquid metals and the investigation of the solidification process of the samples. With the oscillating drop method surface tension and viscosity can be measured and by modulation calorimetry the specific heat is determined.
For the measurement of electrical conductivity, a dedicated electronic device SCE (sample coupling electronic) was developed by our institute.
The solidification can be observed with a high-speed camera (frequency up to 40 kHz) and the growth velocity can be measured. The video images also allow to investigate the shape of the solidification front and the time delay of double recalescences.
The experiments are carried out with the microgravity user support center (MUSC) from the control room in Cologne. The scientists are on site during the experiment runs and can optimize their experiments by commanding from ground. The facility was commissioned in 2014 and first scientific experiments were started in 2015. The EML sample chamber contains 18 samples (called a sample batch). The processing of Batch 1 & 2 is finished and the experiments of Batch 3 are ongoing in orbit. Meanwhile also the ground support program for Batch 4 has started. Up to now more than 50 samples and more than 2000 individual experiment cycles were performed in EML.
As the experiments are quite complex an extensive ground support program is needed to prepare those experiments. In a first step the samples are characterized. The necessary parameters for the planning are measured in a facility with the same coil system and optical path for the pyrometer. So, the reaction of the sample to the heater field, cooling rates etc. can be determined. With these parameters the experiment parameter sets are developed with a software simulation tool in cooperation with the scientists. When the parameter sets are established they are validated in the EML-OM (Operational Model), which is flight-like and provides the same properties as the flight model. These validated parameter sets are then ready for the upload to the ISS.
