NOISE CHARACTERISTICS OF YBCO C-AXIS MICROBRIDGE JUNCTIONS

We present measurements of the noise properties of YBCO c-axis Microbr idge (CAM) Junctions. The junctions have been characterised in terms o f their electrical and noise properties over range of temperature and frequency. The methods used provide both very high sensitivity measure ments in a narrow frequency band (60 kHz), and moderate sensitivity me asurements in a broad band (0.01 - 10 kHz). The normalised levels of c ritical current fluctuations and normal resistance fluctuations are fo und to be comparable to earlier measurements carried out on grain boun dary junctions at both 100 Hz and 60 kHz. The 60 kHz results can be mo delled reasonably successfully with the same model developed to descri be grain boundary junctions. The frequency dependence is close to 1/f, but has some Lorentzian shaped deviations appearing for many of the j unctions examined. These structures are both temperature and bias curr ent dependent.