Details

Autor(en) / Beteiligte

• Wende, G.
• Schubert, M.
• May, T.
• Fritzsch, L.
• Meyer, H.-G.
• Thummes, G.
• Kucukkaplan, Y.
• Qiu, L.M.
• Kohlmann, J.
• Niemeyer, J.
• Hofmeister, H.
• Scheerer, J.

Titel

Josephson voltage standard circuit operation with a pulse tube cooler

Ist Teil von

• IEEE transactions on applied superconductivity, 2003-06, Vol.13 (2), p.915-918

Ort / Verlag

New York, NY: IEEE

Erscheinungsjahr

2003

Quelle

IEEE Xplore Digital Library

Beschreibungen/Notizen

• For a more wide-spread use of Josephson voltage standards, cryogen-free operation, by means of an appropriate closed-cycle refrigerator, is highly desirable. In this work we present a low-noise pulse tube cooler (PTC) that is capable to cool the voltage standard circuits to temperatures below 4 K. As a low loss dielectric waveguide with a very small thermal conductivity a Teflon strip was used for the microwave transmission. The matched transition from the WR12 rectangular waveguide to the Teflon strip and vice versa was made using special exponential tapers. Programmable 1 Volt 14 bit SINIS and 10 Volt SIS arrays assembled in the PTC operated well, i.e., demonstrated a similar performance to that measured in liquid helium. The Josephson junction arrays were integrated in coplanar strips instead of the commonly used microstriplines for the microwave transmission lines. The 1 Volt SINIS array contained 8192 Josephson junctions (JJs). It generated an inherently stable Josephson voltage step of 1.19 V at a driving microwave frequency of 70 GHz. The step width was 150 /spl mu/A and the critical current of the junctions was 550 /spl mu/A. Similar results were obtained under liquid helium cooling conditions. In another experiment a 10 Volt voltage standard chip with 19700 SIS JJs was installed. It was possible to generate stable Shapiro steps at the 10 V level.