Thermal Performances of an Improved Package for Cryocooled Josephson Standards

Durandetto, Paolo; Monticone, E.; Serazio, D.; Sosso, A.

doi:10.1109/tcpmt.2019.2901297

Cited by 7 publications

(8 citation statements)

References 28 publications

(26 reference statements)

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“…Preliminary tests of the bias techniques presented in Section III have been carried out. The experimental setup included a conventional 13-bit PJVS array made of SNIS junctions [17], operated in a Cryomech PT-410 1 two-stage pulse-tube refrigerator with 1 W cooling power at 4.2 K. The PJVS chip was embedded in a special cryopackage similar to that described in [28], suitably tightened to the cryocooler coldplate (Fig. 3).…”

Section: Methodsmentioning

confidence: 99%

Non-Conventional PJVS Exploiting First and Second Steps to Reduce Junctions and Bias Lines

Durandetto

Sosso

2020

IEEE Trans. Instrum. Meas.

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Quantum Digital-to-Analog Converters (DACs) based on programmable Josephson array (PJVS) represent the most widely used quantum standard in ac voltage calibrations. The extension of PJVS frequency above the kHz range appears to be arduous, yet some enhancement are still practicable. In this work we demonstrate the possibility to advantageously operate a conventional binary-divided PJVS array with a reduced number of bias lines. This feature is achieved by exploiting both first and second Shapiro steps along with non-conventional DAC codings. Two newly devised bias techniques are described in detail and preliminary experimental tests on waveform synthesis have been carried out and are presented here.

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Section: Methodsmentioning

confidence: 99%

Non-Conventional PJVS Exploiting First and Second Steps to Reduce Junctions and Bias Lines

Durandetto

Sosso

2020

IEEE Trans. Instrum. Meas.

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“…Proper operation of a Josephson standard in cryocooler is always a challenging task, owing to the tight thermalization requirements [30,31] alongside the need of supplying non negligible dc and rf power for proper operation. We addressed the issue of designing an optimized cryopackage for maximizing the thermal contact between the chip and the cooling surface [32]. It takes advantage of a soft indium foil with a corrugate surface for optimal transmission, achieved by filling the voids between rough surfaces.…”

Section: Pulsed Standards Toward Rfmentioning

confidence: 99%

Advancements in quantum voltage standards for time-dependent signals

Durandetto¹,

Serazio²,

Sosso³

2022

Proceedings of the 25th IMEKO TC4 International Symposium and 23rd International Workshop on ADC and DAC Modelling and Testing

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Quantum voltage standards based on acJosephson effect are in use in metrology since just a few years after the discovery of the physical effect. The role of quantum standards is now crucial following the SI redefinition in 2019 [1]: electrical units are now defined in function of the fundamental constants e (elementary charge) and h (Planck's constant). The extremely low uncertainty in dc measurements, that can be below 1 nV/V at 10 V [2], is stimulating research to extend application to ac and signals arbitrarily changing with time. Approaching the dc accuracy is challenging, however. The two main technologies used for the generation of non-steady voltage signals are programmable and pulsed Josephson junction arrays. In the following we discuss the main advancements obtained with both technologies and the most recent developments, in particular the advantages of He-free device cooling techniques.

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“…The sourcemeter is floating from ground by means of an isolation transformer to avoid interference between simultaneous power and JJ apparent resistance measurements. [8] and cooled with a two-stage pulse-tube cryocooler (Cryomech PT-410 ‡), as shown in Figure 4. Two calibrated silicon diode sensors are employed to determine the temperature of cryocooler coldplate and chip carrier, which should be approximately equal as long as these are in good thermal contact.…”

Section: Josephson Chip and Cryogenic Equipmentmentioning

confidence: 99%

“…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%

“…Therefore, it would be advantageous to directly sense and control the actual chip temperature instead of that of the external sensor, thus reducing the offset in the measurement to a negligible level. JJs for on-chip thermometry have been previously employed to determine the actual chip temperature via the measurement of JJ critical current (I c ) [7,8,10,11]. The novelty here is that the JJ sensor is exploited in an automatic temperature control system through the measurement of a newly-defined parameter, the 'apparent' ac resistance, whose value includes information of the entire JJ current-voltage (IV) curve, and that can be made extremely sensitive to the temperature.…”

Section: Introductionmentioning

confidence: 99%

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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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Thermal Performances of an Improved Package for Cryocooled Josephson Standards

Cited by 7 publications

References 28 publications

Non-Conventional PJVS Exploiting First and Second Steps to Reduce Junctions and Bias Lines

Non-Conventional PJVS Exploiting First and Second Steps to Reduce Junctions and Bias Lines

Advancements in quantum voltage standards for time-dependent signals

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

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