Dresden 2003 – scientific programme
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TT: Tiefe Temperaturen
TT 14: Postersitzung III (Neue u. unkonventionelle Supraleiter, Anwendungen der Supraleitung, Dünne Schichten, JJs und SQUIDs, Schwere Fermionen, Kondo-Systeme)
TT 14.29: Poster
Wednesday, March 26, 2003, 14:30–19:00, P2c
Low noise data acquisition system for measurements of metastable states in Josephson junctions. — •Christian Coqui1, Alexander Kemp1, Jürgen Lisenfeld1, Andreas Wallraff2, and Alexey Ustinov1 — 1Physikalisches Institut III der Friedrich-Alexander-Universität Erlangen-Nürnberg, Erwin-Rommel-Str. 1, 91058 Erlangen — 2Department of Applied Physics, Yale University
The typical lifetime of a metastable state of a Josephson junction has an exponentially decreasing probability distribution. Determination of the characteristic time constants related to a thermal activation or quantum tunneling requires accurate custom-made electronics. We developed a low noise battery powered setup used inside a shielded room. The setup is capable of performing both, ramp and direct life time measurements. Connection to the data acquisition system outside the shielded room is made via optical fibers, which prevent ground loops and high-frequency interference. In experiment we archived a relative current resolution Δ I/I better than 10−4 , which allowed us to observe quantum tunneling and perform level spectroscopy. Direct time measurements cover the time τ range from 100 µ s up to seconds, while current ramp is suitable for τ between 100 ns to 1 ms.