DC-SQUID BASED ON UNSHUNTED JOSEPHSON-JUNCTIONS - EXPERIMENTAL RESULTS

It has been proposed that a new SQUID type be constructed by using uns hunted Josephson junctions instead of resistively shunted junctions. U sing this approach we are able to present a SQUID having a high output dynamic resistance and a device characterized by a negative output re sistance and an extremely low noise. The first mentioned is called a h igh-gain SQUID the latter an unshunted SQUID. This article describes p reliminary experiments obtained from the SQUIDs based on this concept. The iv characteristics are shown to resemble the theorethically predi cted characteristics but the noise performance was higher than expecte d. Most likely the reason for the high noise was the imperfect damping of the SQUID in the frequencies near 1 GHz.