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Hermetically Sealed and Orientation-Independent Vacuum Gauge for Monitoring Deep Vacuum

Description:

 
 

TECHNOLOGY AREA(S): Ground/Sea Vehicles

ACQUISITION PROGRAM: PMS320, Electric Ships Office; PMS501 Littoral Combat Ship Program Office

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the solicitation. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Develop an innovative hermetically sealed, orientation independent vacuum measurement system capable of measuring vacuum levels between 1 Microtorr to 1520 Torr (~2 atm).

DESCRIPTION: Future naval power systems are trending towards a fully integrated power system, which will leverage installed electrical generation to meet the high power demand of future loads. The electric propulsion loads fall within the range of 20-80 MW. Distributing this level of power requires a high power density solution to minimize space and weight. High temperature superconductor (HTS) technology including cables, motors, and generators, is one potential solution. In addition to power applications, HTS is an ideal candidate for degaussing applications due to the high current density with less weight and space. Successful application of this technology requires minimizing heat transfer into the cryogenic spaces where the HTS material resides.

HTS systems utilize a vacuum space in conjunction with multi-layer insulation (MLI) to minimize the heat transfer into cryogenic space. The vacuum degrades over time due to outgassing of materials. As the vacuum degrades, the performance of MLI decreases and higher heat leak into the cryogenic system occurs. Either the result is the inability to maintain the cryogenic environment thereby destroying the superconducting state; or the cryogenic system output needs to be increased to keep up with the higher heat load. A deep vacuum of approximately 1 Microtorr (1E-6 Torr) is an ideal vacuum level; however, in practice, warm vacuum levels approximately 1 Millitorr (1E-3 Torr) are acceptable.

Currently, the only commercially available hermetically sealed vacuum gauges that meet system requirements are spinning rotor gauges which have orientation sensitivity. This orientation sensitivity is problematic when installed on an HTS cable since the final installed orientation is generally not known at the time of manufacture. If the rotor gauge is not in the proper orientation in the final installed position, the vacuum gauge becomes inoperable. Non-orientation sensitive solutions are available, but are not hermetically sealed. Maintaining a high vacuum level is dependent on the exclusion of contaminants within the system, and elimination of sources of vacuum leaks. For these reasons, the Navy needs a hermetically sealed, non-orientation sensitive solution.

The Navy has been developing a high temperature superconducting degaussing system (HTS DG) that has a lower system cost, decreases weight and volume requirements, and offers lower power requirements as compared to a traditional copper-based degaussing system. This topic seeks to develop a component that replaces a current vacuum gauge that has significant limitations for use in the field. The orientation sensitivity of the existing gauge results in inoperability on an installed HTS DG cable leaving vacuum levels in the cryostats unknown. The component developed through this topic will have utility in HTS Motors, generators, power cables, and any other vacuum insulated system that requires monitoring deep vacuum levels.

The objective of this topic is to develop an innovative vacuum sensor capable of measuring vacuum in the range of 1-Microtorr to 1520 Torr (~2 atm) while being insensitive to installation orientation. High precision vacuum readings are not required and an error of 10-20% of the reading is acceptable. The sensor must be rugged enough to be used in a shipboard environment and must meet all qualification requirements including shock and vibration, which will be tested by the Navy. Two potential approaches to using these gauges on the ship are as either an active part of the HTS system that continuously monitor the vacuum or the gauge may be used for periodic checks, similar to the current gauges. Use as an active part of the system is preferable solution as it has the potential to reduce manning requirements for periodic vacuum level evaluation. The final vacuum sensor is expected to be low cost ($100-$500), compact in size (3” x 2”dia), and have a service life of 30 years.

PHASE I: The small business will develop a concept for a hermetically sealed, orientation independent vacuum measurement system. Feasibility of an innovative vacuum sensor that meets the needs of the Navy as defined in the description will be demonstrated by modeling and simulation. The company will identify the technical feasibility of the proposed concept and demonstrate the concept through modeling, analysis, and/or bench top experimentation where appropriate. The Phase I final report shall capture the technical feasibility and economic viability for the proposed concept. The Phase I Option, if awarded, should include the initial description and capabilities to build the unit in Phase II.

PHASE II: The small business will develop and fabricate a prototype vacuum gauge based on the Phase I work and Phase II Statement of Work (SOW) for demonstration and characterization of key parameters and objectives. At the end of Phase II, a prototype vacuum sensor shall be delivered to the Navy for further performance testing. Based on lessons learned in Phase II through the prototype demonstration, a substantially complete design of a vacuum sensor should be completed that would be expected to pass Navy qualification testing including shock and vibration.

PHASE III DUAL USE APPLICATIONS: The small business will be expected to support the Navy in transitioning the technology for Navy use onboard ships. This includes teaming with appropriate industry partners to provide a fully qualified vacuum sensor for integration and use in HTS systems for degaussing and power distribution. Private Sector Commercial Potential: Vacuum sensors have wide spread industrial and academic use in cryogenics, superconductivity, and the semi-conductor industry making it broadly applicable to the commercial world.

REFERENCES:

  • J.T. Kephart, B.K. Fitzpatrick, P. Ferrara, M. Pyryt, J. Pienkos, E.M. Golda, “High temperature superconducting degaussing from feasibility study to fleet adoption,” Transactions on Applied Superconductivity, Vol.21, 2010, 2229. http://ieeexplore.ieee.org/Xplore/defdeny.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fstamp%2Fstamp.jsp%3Ftp%3D%26arnumber%3D5672800%26userType%3Dinst&denyReason=-134&arnumber=5672800&productsMatched=null&userType=inst
  • R. K. Fitch, "Total pressure gauges," Vacuum, vol. 37, pp. 637-641, 1987. http://www.sciencedirect.com/science/article/pii/0042207X87900492
  • F. Völklein and A. Meier, "Microstructured vacuum gauges and their future perspectives," Vacuum, vol. 82, pp. 420-430, 12/12/ 2007. http://www.sciencedirect.com/science/article/pii/S0042207X07003065
  • Y.-T. Wang, T.-C. Hu, C.-J. Tong, and M.-T. Lin, "Novel full range vacuum pressure sensing technique using free decay of trapezoid micro-cantilever beam deflected by electrostatic force," Microsystem Technologies, vol. 18, pp. 1903-1908, 2012/11/01 2012. http://link.springer.com/article/10.1007%2Fs00542-012-1468-2
  • MIL-S-901D, MILITARY SPECIFICATION: SHOCK TESTS. H.I. (HIGH-IMPACT) SHIPBOARD MACHINERY, EQUIPMENT, AND SYSTEMS, REQUIREMENTS FOR (17 MAR 1989); http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-S/MIL-S-901D_14581/

KEYWORDS: HTS; superconductivity; hermetic sealed vacuum gauge; orientation independent vacuum gauge; vacuum maintenance and measurement; vacuum spinning rotor gauge

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