N121-079 TITLE: Design an Expert System to Automate Cool-down of Superconducting Electronics

TECHNOLOGY AREAS: Sensors, Electronics, Battlespace

ACQUISITION PROGRAM: ONR Silk Thread FNC FY13 start

OBJECTIVE: Determine a set of environmental criteria and design an expert system programmed to automatically decrease the temperature of a digital superconducting circuit through the transition temperature of the electrode material so that there is no flux trapping and produce a method of self-testing the circuit performance. The goal is to avoid the requirement of a highly trained operator to use such circuits in a naval radio frequency (RF) transceiver context.

DESCRIPTION: Superconducting electronics have the potential to enable development of superior performance, acquisition and logistics cost saving, ultra wide band, all purpose RF systems. First packaged prototypes have demonstrated technology readiness level (TRL) 5 capabilities in DoD labs when started and left running for months. However, to be interesting for fielded applications, they need to be operated with little to no human interaction. While NASA has remotely operated passive systems based on the same cryo-coolers for some years, little is known regarding the details of the thermal cool-down influence resultant RF system performance. There is also no standardized method of confirming such a system is operating properly. Thus the objective of this effort would be to establish a quantitative test for the occurrence of flux trapping and experimentally determine the relationship between such an occurrence and the system's thermal history.

Current State-of-the-Art: The existing cooler device is turned on and after the circuit reaches 4 Kelvin an expert tests whether the one-of-a-kind system is behaving as expected. If not, the temperature is recycled to above 10 Kelvin and back down. Currently, there is no diagnostic that can be run warmer than 4 Kelvin to determine whether a given die will need 1 or 5 thermal cycles to operate properly, nor is there any automated or standardized test for how well it is operating.

PHASE I: Develop and demonstrate the technical concept for how the ambient magnetic field will be measured, how the temperature of the circuit will be monitored and controlled, and how the circuit performance will be measured. Methods involving conduction cooling rather than immersion or convection cooling are more appropriate for the expected scale of deployed naval systems.

PHASE II: Demonstrate an integrated cryopackaging system that includes the techniques developed in Phase I and uses a closed cycle cooler to handle at least one working analog-to-digital convertor (ADC) die (to be supplied as government furnished equipment). Document the success of the self-test module and generalize the requirements regarding the magnetic environment when the transition temperature is crossed. Assess additional issues expected for dramatically larger multi-chip modules and how to combine with both active B field cancellation and the desire to change circuit modules while the rest of the system stays cold.

PHASE III: Future naval capability programs at ONR are expected to contain field demonstrations of superconducting RF hardware. It is very desirable that these demonstrations be performed with remotely operated hardware.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Superconductive electronics has the potential to dramatically improve RF sensitivity and linearity and to produce higher energy efficiency, high throughput computing, of both conventional logic and quantum styles. The RF applications are particularly relevant to multi-user telecom ground stations. The computing applications require circuits more than a 1000 fold more complex than today's die to be fabricated and deployed. Without the ability to remotely operate both kinds of systems, the commercial applications will be very limited.

REFERENCES:
1. Y. Polyakov , S. Narayana and V. K. Semenov "Flux trapping in superconducting circuits", IEEE Trans. Appl. Supercond., Vol 19, pp. 640-643 (2009).

2. Supradeep Narayana and V.K. Semenov," Comparison of flux trapping in power independent and RSFQ D flip- flops", 15th US workshop in Superconducting devices and circuits (2007).

3. Bermon, S., Gheewala, T. "Moat Guarded Josephson SQUIDS", IEEE Transactions on Magnetics, Vol. 19 Issue 3, pp. 1160 � 1164 (May 1983).

KEYWORDS: flux trapping; thermodynamic processes; low magnetic fields; thermal and magnetic fluctuations; expert systems; circuit self-test

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