Josephson voltage standard circuit operation with a pulse tube cooler

Abstract

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 8,192 Josephson junctions (JJ's). 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 A and the critical current of the junctions was 550 A. Similar results were obtained under liquid helium cooling conditions. In another experiment a 10 Volt voltage standard chip with 19,700 SIS JJ's was installed. It was possible to generate stable Shapiro steps at the 10 V level. Index Terms-Cryocooler, Josephson junctions, microwave dielectric waveguide, voltage standard.

Damping of Intrinsic Temperature Oscillations in a 4 K Pulse Tube Cooler by Means of Rare Earth Plates

“…FIGURE 4 displays the frequency spectrum measured at the base temperature <T 9 > = <T 10 > = 2.2 K of the cooler. Besides a peak at the fundamental frequency of 1.2 Hz, the spectrum shows peaks up to the 3 rd harmonic for T 9 , while for T 10 there is only a much lower peak at the fundamental frequency, which shows that higher frequencies are more strongly damped, as predicted by equation (2).…”

“…For example, the cooling power at 4.0 K is reduced from 410 mW without ErNi plate to 100 mW with plate No.2 (damping factor ∼31 at 4 K). However, this is still sufficient for the cooling of Josephson voltage standards [2].…”

“…For a more wide-spread use of such voltage standards, cryogen-free operation by means of an appropriate cryocooler is highly desirable. In one of our prior projects, an in-house made two-stage pulse tube cooler (PTC) was successfully employed for the operation of a 1 V Josephson voltage standard near 4 K [2]. The experiments showed an unfavorable influence of the temperature oscillations on the current-voltage characteristics of the circuit that reduces the accuracy of the voltage standard.…”

A Cross-Type SNS Junction Array for a Quantum-Based Arbitrary Waveform Synthesizer

“…Since about 1990 Josephson voltage standards with dc voltage references of 1 and 10 Volt [1] have been in use in national, industrial and military standards laboratories around the world. The development of programmable voltage standards [2], [3] which provide intrinsically stable and selectable voltages of up to 1.2 V, is largely finished.…”

A Lumped Array Josephson Pulse Quantizer for Quantum-Based Arbitrary Waveform Synthesizers

“…Since about 1990 Josephson voltage standards with dc voltage reirences of 1 and 10 Volt [1] have been in use in national, industrial and military standards laboratories around the world. The development of programmable voltage standards [2,3], which provide intrinsically stable and selectable voltages ofup to 1.2 V, is essentially finished.…”