Modeling of tunnel diode oscillators and their use for some low temperature investigations
Review of Scientific Instruments
The simple method of modeling of tunnel diode ͑TD͒ oscillators' work is described, and may be applied also to the other types of negative-differential conductance oscillators. In particular, the calculation of the harmonic oscillation amplitude is performed by the energy balance method, based on TD measured the current-voltage characteristic' ͑I -V curve͒, using only one fitting parameterthe tunnel diode's measured bias at which oscillations are quenched by means of which the oscillator's
... oscillator's effective total losses are determined also. The formula for calculation of the TD generator's frequency is derived; it agrees with experiment and permits determination of its dependence on the radiotechnical scheme's elements and TD I -V curve's shape. The results of the calculation in comparison with the experiment are reported for the oscillators of various constructions operating at different conditions. For this, more attention is given to the constructive solutions applied in the low temperature experiments. Examples of the TD oscillators' use in cryogenic techniques as well as in the superconducting detectors of particles and radiation are presented. The oscillators described generate, under the certain conditions, low-amplitude (Ͻ40 mV) sinusoidal signals with a highly stable frequency ͑not worse than ⌬F/Fϭ10 Ϫ9 /min at liquid-helium temperatures͒ and low intensity of higher harmonics in the soft mode. The power released is less than 10 W and the measuring rf magnetic field's amplitude at a sample, placed inside or near the oscillator coil, is less than 1 mOe. Using designed facilities we have already detected normal-to-superconducting phase transitions of tin grains with diameters of about 2 m and phase transitions in micrometer thick and 20 m 2 high-T c superconducting films.