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The microwave properties of a YBa2Cu3O7-x bulk sample are investigated using a cavity perturbation technique. The sample is placed in the field of a microwave TM011 mode cylindrical cavity operated at about 2.86 GHz, and the unloaded quality factor Q U is measured in the temperature range above 80 K. It is found that a sharp reduction of the Joule loss in the sample begins at an onset temperature of about 90 K. The formula for the microwave conductivity is also derived theoretically and the conductivity of the sample is evaluated from the results of Q U measurements of the cavity with and without the sample.

The influence of the drawing process in optical fibers on the radiation resistance property was investigated. The ESR spectra for the optical fibers drawn under various conditions were measured at room temperature (R.T.) or 77 K. The fibers were drawn at three different temperatures (high, medium and low) and the drawing velocity was kept constant. The drawing defects were abundantly detected at R.T. in the sample drawn at high temperature. Many non-bridging oxygen hole centers (NBOHC) induced during the drawing process were observed at 77 K. The formation of NBOHC was also discussed.

Well known microwave cavity measurements for determining the plasma density n and the collision frequency v of electrons was improved to be applicable in a simple way to decaying plasmas. Previously, two different microwave frequencies have been required to determine both of the plasma prameters. In the present study we analyzed the general properties of a cavity, and propose an improved method to measure, simultaneously, n and v in a decaying plasma by using only one frequency. The principle is that both parameters are determined by detecting the phase in addition to the absolute value of the transmission coefficient through the cavity. Moreover, we derive various formulas that are useful for measuring both parameters under various assumptions. Various experimental demonstrations for our methods are carried out.

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