We are developing a flat coil-based tunnel diode oscillator technique, which can be used for detection of changes of distances with ∼ 1 Åabsolute and ∼ 10-6 relative resolution. It is also an excellent radio frequency Q-meter for detection of changes ∼ 10-9 W of absorption in small-volume specimens. We are using it for high-resolution study of various weakly expressed peculiarities of the superconductive state in thin plate-like HTS (in particular, the peculiarities of vortex motion, allowing determination of some material parameters). But, for correct extraction of physical characteristics by this sensitive technique there is need to calibrate properly both the shifts in resonant frequency (inductance change) and the amplitude (Q-factor change) for the technique. The problem here is much complicated compared with a solenoid coil-based traditional technique. In this report we discuss only the method of calibration of coil's resonant frequency change (testing field's configuration change) with copper plates, allowing correct transfer of the measured shifts of frequency to changes of distance from the coil face. The results show an exponential decrease of the sensitivity with a distance from the coil. The data allow estimating the optimal sizes for the samples for a given coil design. For such samples the frequency shifts are proportional to the sample area. The data shows also the imperfections of the used flat coil's design causing some decrease of sensitivity in a current technique. We discuss ways to make such a perspective technique much better.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering