N122-142 TITLE: Compact High-Power Broad-Band Spherical PiezoCrystal Acoustic Source for Countermeasures

TECHNOLOGY AREAS: Materials/Processes, Sensors, Electronics

ACQUISITION PROGRAM: PMS 415 Undersea Defensive Systems

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Design, build, and test a compact, high power, broad bandwidth, highly efficient acoustic source made from relaxor piezocrystals whose shape approximates a sphere.

DESCRIPTION: Acoustic countermeasures, deployed from ships and submarines, serve as decoys by mimicking the acoustic signature of the vessel. These autonomous devices require a highly efficient, high-power, broadband, compact acoustic source to achieve their goals. The combination of the most effective acoustic radiator design (i.e., a sphere) and the new high-coupling, high-strain relaxor piezocrystals provides an optimum combination to meet these exacting requirements. The primary technical challenge is to devise a cost-effective method of making a tiled approximation to a sphere; much as current piezocrystal cylindrical transducers are tiled approximations to a cylinder. Other issues to be addressed, primarily by modeling, include specifically the actuation mode (d31 or d33) of the crystals, whether a fully active tiling is appropriate or whether some passive tiles should be included, and the implications of these choices for the drive electronics.

In these applications both cylindrically and spherically shaped sources made from legacy piezoceramics have been employed with good results. Segmented cylinders of the relaxor piezocrystals provide a dramatic enhancement over the legacy piezoceramic cylinders, matching their acoustic performance in a package one hundredth the size requiring only half the energy. A tiled sphere (like a soccer ball) of piezocrystals will provide a similar step improvement over legacy piezoceramic technology.

PHASE I: Design a transducer that closely approximates a sphere using tiles made from plates of relaxor piezocrystals. Model the acoustic performance of the design: crystallographic orientation of the plates, location of the electrodes, dimensions of the components and overall transducer size for the frequency bands appropriate for acoustic countermeasures. Devise a method to assemble a notional transducer and validate the feasibility of the assembly technique by making at least one example and measuring the acoustic performance of that example. A Phase I Option could include assembly of additional samples and measurement of their acoustic performance.

PHASE II: Using the results from Phase I, vary the design parameters of the candidate transducer configuration to optimize its acoustic performance as a countermeasure source. Optimize the transducer assembly method, then build and measure the acoustic performance of at least two devices. Phase II work that focuses on a specific device may be classified.

PHASE III: Transition a compact, high power, broad bandwidth, highly efficient acoustic source made from relaxor piezocrystals whose shape approximates a sphere to upgrade the performance of present countermeasure devices and to make new, improved countermeasures feasible into a program of record.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The compact, broadband, highly efficient acoustic source developed in this effort will find applications in a broad spectrum of civilian underwater sonar systems in applications ranging from bottom profiling through obstacle avoidance and acoustic beacons to acoustic communications modems.

REFERENCES:
1. Aronov, Boris, David A. Brown, Xiang Yan, and Corey L. Bachand. 2011. "Modal Analysis of the Electromechanical Conversion in Piezoelectric Ceramic Spherical Shells." Acoustical Society of America 130, no. 2: 753-763. Accessed December 2, 2011. doi: 10.1121/1.3593364.

2. Powers, James M., Mark B. Moffett, and F. Nussbaum. 2000. "Single Crystal Naval Transducer Development." Proceedings of the IEEE International Symposium on Applications of Ferroelectrics, Honolulu, Hawaii, July 21 - August 2, 2000: 351-354. Accessed December 2, 2011. doi: 10.1109/ISAF.2000.941570.

KEYWORDS: Single crystal; transducers; countermeasures; spherical; piezocrystals; broad bandwidth

** TOPIC AUTHOR (TPOC) **

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