Circuits for Josephson Voltage Standards
Research: JAWS
We investigate Josephson series arrays operated by short current pulses, in order to generate voltages of arbitrary waveforms. The series arrays for use in this JAWS (Josephson Arbitrary Waveform Synthesizer) consist of SNS junctions (a trilayer of Superconductor / Normal metal / Superconductor). We use Niobium as a superconductor and Hafnium-Titanium as a normal metal. Due to the low electrical resistance of Hafnium-Titanium resulting in high current densities during operation, we want junctions of dimensions of only 1 µm x 1 µm, which we fabricate using electron beam lithography.
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Measured frequency spectrum of a 600-Hz synthesized sine wave. The array consists of 1024 SNS junctions resulting in a voltage of 10 mV. The strong suppression of higher harmonics clearly demonstrate the correct array operation.
