The approach is to first develop the technique of measuring the radiative properties of high-temperature liquid and undercooled liquid materials by use of FTIR spectroscopy. The sample will be positioned in a containerless environment by electromagnetic levitation to eliminate any crucible induced contamination or nucleation of the undercooled liquid. The sample temperatures will be measured by an optical pyrometer and the radiated spectra of the sample in the wavelength range 2-20 um will be recorded by FTIR spectrometer. The spectrum of a standard sample will be measured and spectral hemispherical emissivity determined by comparison of the sample spectrum to the standard spectrum. The standard sample will be a blackbody hole in a tungsten sphere.
We have established a UHV (Ultra High Vacuum) system for electromagnetic levitation and sample positioning. In this system, a copper baffle was also designed and incorporated to protect the main turbomolecular pump. A ZnSe window for the light collection in the wavelength region of interest has also been mounted in the UHV chamber.
We have also designed and built the coaxial RF transformer and coil system for independent levitation and heating of metals. In this coil system, the best coupling between the RF generator and coils and the best stability of the levitated samples will be realized and undercooling can be easily achieved by adjusting the power to heating coils without affecting the levitation.
We also tested several optical pyrometers from Mikron on levitated liquid and solid metals. A pyrometer (M190, Mikron) with fast response time and small field-of-view which will be used to measure sample temperatures in this project has been purchased. The software for data acquisition from the pyrometer has been developed.
Both hardware and software of the FT-IR spectrometer (M2400-C, MIDAC) have been evaluated. Initial test have been carried out to measure the emission characteristics of different objects.
The optical system has been designed and is being tested in the lab. Key parts in the optical system have been ordered. The hardware for the optical system is currently under construction.