SUPERCONDUCTIVE EFFECTS IN THIN FILMS
Abstract
Improvements were made in the measurement of microwave cavity Q. A cw local oscillator beating against the fm signal klystron generates a band of beat frequencies. A tunable radio receiver selects the desired narrow band. After shaping by an RC circuit, this band is used to trigger a pulse generator resulting in a pair of very sharp markers separated by a controllable and accurately measurable amount in frequency. Thus the bandwidth of the cavity characteristic can be accurately determined leading to a much improved Q measurement. Despite the use of thin Al films in low resistance crossings, or the use of poor RC crossings, no quantum effects were observed in the presence of microwave power. It was noted that magnetic flux was sometimes trapped in the films forming the sample. This resulted in substantial rounding of the sharp corner in the I-V characteristic and care was taken to avoid the effect. The square wave response of a sample operated as a microwave detector was examined up to the limit of the oscilloscope used, less than 1 megacycle. The tunneltron response was found not limiting. Zero-voltage currents associated with the tunneling of electron pairs have been observed in all low resistance samples. An ac technique was used which permitted a demonstration that these currents were not due to super conducting short circuits.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 15, 1963
- Accession Number
- AD0407317
Entities
People
- S. Shapiro
Organizations
- Arthur D. Little