DEVELOPMENT OF SPECTROMETER AT MICROWAVE- AND MILLIMETER WAVE FREQUENCIES WITH CONTINUOUS FREQUENCY SWEEP

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In this research project, we tried to fabricate a complex-impedance measurement system with which data can be taken for swept frequencies in a continuous manner. In particular, we tried to construct (1) a system where we put a sample in a waveguide, and (2) a system with using hybrid-type cavity resonator, at the very beginning of the project. However, later, we found that even the former method is quite difficult unexpectedly. Thus, we changed our Plan at the beginning of the 2ィイD1ndィエD1 year, and decided to focus on the 1ィイD1stィエD1 method. Now, at the end of the project, we made the following achievements.(1) We constructed a complex impedance measurement system with a continuous swept frequencies which can be operated up to 3 MHz. Using a reference material, me confirmed that the complex conductivity can be measured correctly. Next, we tried to obtain the complex conductivity of a high-temperature Superconductor, BiィイD22ィエD2SrィイD22ィエD2CaCuィイD22ィエD2OィイD2yィエD2(abbreviated as BSCCO bel … More ow) bulk single crystals. However, we have not succeeded in obtaining the data of the complex couductivity of the material, yet. The main origin of unsuccessful measurement is considered to be the low value of resistance of samples we used, which is almost within the noise level of our system. We are now trying to insert an amplifier at the receiver of the system, and also planning a measurement using thin film samples.(2) We Succeeded in measuring the complex impedance of YBaィイD22ィエD2CaCuィイD23ィエD2OィイD2yィエD2 (YBCO) in the mixed state as a function of magnetic field for several different frequencies, for the 1ィイD1stィエD1 time. From the data, we succeeded in obtaining the correct value of the viscosity of vortices of YBCO. The result definitely show that the core of the vortex in this material is almost like a classical core. We also confirmed the similar result in BSCCO for wide range of carrier concentrations, which indicates that the above picture is quite universal to the vortex core of high-temperature superconductors. Less