Practical Operation of Cryogen-Free Programmable Josephson Voltage Standards

Schwall, Robert E.; Zilz, D P; Power, Jeffrey; Burroughs, Charles J.; Dresselhaus, Paul D.; Benz, Samuel P.

doi:10.1109/tasc.2011.2104930

Cited by 13 publications

(4 citation statements)

References 15 publications

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“…This feature of PJVS arrays has been exploited in this work by using some segments as power source and others as temperature sensor, using the procedure explained in Sec. III and previously adopted in [20] and [21].…”

Section: B Josephson Chipmentioning

confidence: 99%

Thermal Performances of an Improved Package for Cryocooled Josephson Standards

Durandetto

Monticone

Serazio

et al. 2019

IEEE Trans. Compon., Packag. Manufact. Technol.

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Section: B Josephson Chipmentioning

confidence: 99%

Thermal Performances of an Improved Package for Cryocooled Josephson Standards

Durandetto

Monticone

Serazio

et al. 2019

IEEE Trans. Compon., Packag. Manufact. Technol.

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“…10 V PJVS devices are fabricated on a substrate of highpurity [15], 76.2 mm diameter silicon with 150 nm of thermal oxide. All lithography steps in this process are performed using an i-line wafer stepper with resolution of 0.4 μm.…”

Section: Fabrication Processmentioning

confidence: 99%

Junction Yield Analysis for 10 V Programmable Josephson Voltage Standard Devices

Fox

Dresselhaus

Rüfenacht

et al. 2015

IEEE Trans. Appl. Supercond.

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Analysis of the Josephson junction yield in the National Institute of Standards and Technology 10 V Programmable Josephson Voltage Standard (PJVS) has been performed by fabricating and measuring over 25 million Nb/Nb x Si 1−x /Nb junctions. Using the 265 116 junctions per PJVS device, it was possible to measure Shapiro steps on current voltage curves and then estimate the number of single-junction defects within these long arrays. By comparing the results of a quantum-based measurement to a model simulating junction defects, the quantity and magnitude of a small number of junction defects can be estimated from an array of many thousands of junctions. Understanding the source of junction defects in the fabrication process is important for maximizing yield and uniformity, both of which directly relate to the current margin of the quantized voltage step. We have recently fabricated 18 imperfect but usable PJVS devices and 16 that were free from defects, many with n = 1 Shapiro step margins approximately equal to 2 mA. The best of these wafers had a junction defect density of around 3 in a million.

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“…The residual thermal resistance is not low enough in the most demanding conditions and particular care is required in the design of a chip carrier to reduce thermal gradients, mainly at the interfaces between solid bodies. For JVSs working in the high-vacuum environment of a cryocooler, special cryopackages have been designed [6][7][8][9], exhibiting thermal resistances between chip and cold heat sink of few kelvin per watt. The case of JVS is particularly interesting and challenging: power levels of some tens of milliwatt are generally dissipated within a JVS, possibly causing its actual temperature to differ from that measured with the the sensor by hundreds of millikelvin.…”

Section: Introductionmentioning

confidence: 99%

Using a Josephson junction as an effective on-chip temperature sensor

Durandetto¹,

Sosso²

2021

Supercond. Sci. Technol.

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Temperature sensing and control are essential in experiments running in cryocooled systems, as with the case of liquid helium-free superconducting devices. A Josephson junction as on-chip temperature sensor operated in ac provides the highest sensitivity and minimal power loading to the cryogenic environment, thanks to the noise rejection of lock-in detection. To demonstrate the advantages of on-chip sensing, we tested it with a Josephson voltage standard array in cryocooler and compared with the conventional case of a sensor on the cold surface of the refrigerator, showing that the power dissipated within the chip may further increment the device temperature up to some tenths of kelvin. An ac Josephson junction sensor is proven to be capable of directly stabilizing the temperature of the superconductive circuit from fluctuations of dissipated power during operation. Reliability issues related to flux trapping are discussed and solutions are proposed suited to different applications. Overall, on-chip control with ac Josephson temperature sensing has the advantage of avoiding the complexities in minimization of cryogenic thermal links, virtually reducing to zero the contact resistance and keeping the operating temperature of the superconductor constant, independently of instantaneous operating power.

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Practical Operation of Cryogen-Free Programmable Josephson Voltage Standards

Cited by 13 publications

References 15 publications

Thermal Performances of an Improved Package for Cryocooled Josephson Standards

Thermal Performances of an Improved Package for Cryocooled Josephson Standards

Junction Yield Analysis for 10 V Programmable Josephson Voltage Standard Devices

Using a Josephson junction as an effective on-chip temperature sensor

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