TECHNOLOGY AREAS: Sensors, Electronics

ACQUISITION PROGRAM: PMS 502, CGX Program Office, ACAT I

OBJECTIVE: Develop distributed temperature sensors for use in cryogenically cooled thermal paths for High Temperature Superconductor (HTS) applications.

DESCRIPTION: Legacy sensors used to monitor temperature in cryogenic environments include resistive elements and diodes. While these devices perform adequately, each sensor must be addressed with a separate set of up to four wires and is not designed to measure distributed temperatures over a large area. This creates a problem for naval applications such as HTS degaussing cables or HTS power cables where the cryogenic region can be up to 200 meters in length and requires temperature measurements every 1 meter. The successful installation and termination of up to 800 36-gauge wires also raises concerns in design (ingress/egress, a critical issue in protecting cryogenic environments), logistics, reliability, and acquisition & life cycle costs. In addition, the legacy sensors may be susceptible to electromagnetic interference - a major problem if monitoring on power cables.

The Navy seeks technology capabilities to measure and monitor temperatures along a length of cryostat for its HTS degaussing applications and potential future power cable applications. The temperature range of interest is 25K to 300K but technology solutions capable of measuring even lower temperature would be desirable. It would be expected that the distributed temperature sensors would be at multiple locations, on the order of ever 1 meter or so, along the length of a cryostat. Individual sensor leads must be minimized as it is infeasible to have hundreds of cryogenic instrumentation feed-throughs. While sensor topologies are not being limited in this solicitation, fiber optic based sensors that use Brillouin scattering, or Bragg grating wavelength shift appear to have favorable qualities for this application. The manufacturing process of incorporating the distributed sensor during HTS wire cabling should be considered to ensure adequate ruggedness of the sensor. Given the environment, the sensors must also be immune to EMI.

PHASE I: Demonstrate the feasibility of a novel, sensor technology able to operate with Navy cryogenic systems as defined above. Perform bench top experimentation, where applicable, as a means of demonstrating the identified concepts. Establish validation goals and metrics to analyze the feasibility of the proposed solution. Provide a Phase II development approach and schedule that contains discrete milestones for product development.

PHASE II: Develop, demonstrate and fabricate a prototype as identified in Phase I. In a laboratory environment, demonstrate that the prototype meets the performance goals established in Phase I. Verify final prototype operation in a representative laboratory environment and provide results. Develop a cost benefit analysis and a Phase III installation, testing, and validation plan.

PHASE III: Transition the technology to commercial and military cryogenic or superconducting applications. Working with government and industry, install onboard a selected Navy ship and conduct extended shipboard testing.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: A distributed cryogenic temperature sensor maybe of use in land based HTS power cables. When land based HTS power cables transition from R&D project to commercial installations, monitoring temperatures will help assess conditions based maintenance for regions of the cable that may see damage.

REFERENCES:
1. Gupta, Sanjay, et. al. "Fiber Bragg Grating Cryogenic Temperature Sensors", Applied optics, Vol.35 No.25, September 1, 1996.

2. Toru Mizunami, et. Al., "High-Sensitivity Cryogenic Fibre-Bragg-Grating Temperature Sensors Using Teflon Substrates", Meas. Sci. Technol. 12 914-917, 2001.

KEYWORDS: Fiber optic; Sensor; Cryogenic; Superconductor; HTS; Temperature; Thermal Path.

** TOPIC AUTHOR (TPOC) **

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