High-performance waveform-sampling analysis based on digital multipoint signal averaging

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Abstract
This paper describes a versatile digital multipoint waveform-recording system utilizing computer-aided signal-averaging procedures. Basically, it consists of a Biomation 8100 transient recorder coupled to a DEC PDP 11/04 computer via an electronic interface device and a CAMAC I/O-register NE 9066 supported by an appropriate software system. Additional use of an extremely low-noise wideband preamplifier system together with proper shielding, filtering, and differential measuring techniques minimize the disturbing influence of random and coherent electromagnetic noise. Employing our waveform-recording system to sensitive time-resolved flux-flow measurements in superconductors yields both a voltage resolution approaching 1 nV and a time resolution of 10 ns at a recording bandwidth of 25 MHz. Such a novel scheme of high-performance waveform-sampling analysis yields an overall efficiency limited at the characteristic rise-time sensitivity product of about 10−17 V s, corresponding to a magnetic flux sensitivity far better than a single quantum. An outline of the present uses and future prospects indicates that this method represents an important tool in such advanced fields as low-temperature solid-state physics and cryoelectronics and deserves more attention both from a fundamental point of view and for many technological applications.