N121-046 TITLE: Spatially-Distributed Electron Beam Technology for Millimeter-Wave Amplifiers

TECHNOLOGY AREAS: Sensors, Electronics

ACQUISITION PROGRAM: PEO IWS 2.0, Surface Electronic Warfare Improvement Program (SEWIP), ACATII

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: To develop and evaluate a spatially-distributed electron beam gun and beam transport system suitable for use with a high power millimeter-wave vacuum electronics amplifier.

DESCRIPTION: Radio-frequency (RF) amplifiers are a key component in Navy/DoD transmitters used for electronic attack, high-data-rate communications, and radar. In the millimeter-wave frequency regime, higher RF output power is needed for improved platform self-protection against emerging threats, to extend the range of radar and communications systems, and to provide all-weather operational capabilities. This SBIR will develop the enabling technology for a new class of compact amplifiers to meet these needs, increasing millimeter-wave amplifier RF output power by more than a factor of two over the current state-of-the-art and decreasing the amplifier system cost per watt of output power.

Vacuum electronic (VE) devices have a demonstrated ability to deliver single-device power in excess of projected solid-state amplifier power, particularly at millimeter-wave (MMW) frequencies. For this reason, vacuum electronic slow-wave amplifiers are expected to be key elements in future MMW transmitters for electronic attack, high-data-rate communications, and radar systems. However, overall transmitter weight and size must be reduced, particularly for weight- and space-constrained platforms, while transmitter power, efficiency, and bandwidth must be improved. Although extremely high powers are available from gyro-amplifiers, these devices are not conducive to compact form factors. Slow-wave, linear beam radio-frequency (RF) power amplifiers have the potential to meet size and weight goals but require development to meet the needs of applications requiring kilowatts of continuous-wave (CW) power.

Current slow-wave, linear beam MMW VE amplifiers are driven by a single axisymmetric electron beam. At cathode voltages below 25 kV (necessary to minimize system weight and volume), space-charge effects place a limit on the maximum beam current that can be propagated without de-bunching, hence limiting the maximum beam power to ~7 kW and the RF output power to less than 1 kW CW. To address emerging threats and applications, higher RF output power and bandwidth are desired, necessitating higher beam power. Such power levels are not achievable with existing electron gun technology. The goal of this SBIR is to develop a new electron gun technology that is capable of >30 kW of total electron beam power - a more than four-fold increase in the state-of-the-art - that will in turn facilitate a more than two-fold increase in RF output power (>2 kW CW).

To facilitate the development of higher power MMW VE amplifiers, this topic is soliciting innovative electron gun approaches based on spatially-distributed electron beam technology such as multiple pencil beams or elliptical/rectangular cross-section electron beams. Spatially-distributed electron beam devices are an emerging technology that has been made possible by recent advances in three-dimensional computational modeling and in manufacturing and materials technology. The non-axisymmetric nature of the beam generation, propagation, and collection presents many technical challenges and requires the development of innovative solutions. Performance goals include >30 kW of total beam power with cathode voltages less than or equal to 25 kV (to meet compact system footprint goals and to minimize system cost); and a beam optics and beam transport system design with 100% transmission from the gun to the electron collector in the absence of RF drive. While the primary focus of the research is on spatially-distributed gun development, candidate gun designs must demonstrate that they can be integrated with a beam-wave interaction circuit capable of producing >2 kW of broadband MMW RF output power at frequencies up to 45 GHz. An expected by-product of the research and development of the hardware is the establishment of a design methodology, scalable in power and frequency, which makes use of and expands upon the potential of modern 3D design codes.

PHASE I: The company will develop concepts for a spatially-distributed electron beam gun, transport system, and beam-wave interaction circuit that meets the requirements described above. The company will demonstrate the feasibility of the concepts in meeting Navy needs and will establish that the concepts can be feasibly developed into a useful product for the Navy. Feasibility determination will include analytical and/or computational modeling of potential designs, including the effect of beam space-charge, emittance (thermal beam), and realistic magnetic field profiles. Concepts must be capable of meeting all requirements for the MMW amplifier. The company will provide a Phase II development plan with performance goals and key technical milestones.

PHASE II: Based on the Phase I research results and the Phase II development plan, the company will design and fabricate a prototype spatially-distributed electron beam gun and create an engineering design for the beam transport system and collector. The prototype and overall design will be evaluated to determine its capability in meeting the performance goals defined in Phase I. Evaluation results will be used to refine the prototype into an initial design that will meet Navy requirements. The company will conduct a cost analysis of a pre-production prototype and will prepare a Phase III development plan to transition the technology for Navy use.

PHASE III: If Phase II is successful, the company will be expected to support the Navy in transitioning the technology to Navy use should a Phase III award be made. The company will integrate the spatially-distributed electron beam gun, transport system, and collector together with an interaction circuit for evaluation and will assist in its incorporation into a Navy/DoD relevant prototype transmitter. The company will support the Navy in the certification and qualification of the system for further testing in operationally relevant environments.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Commercial applications of spatially-distributed beam amplifier technology include broadband high-power amplifiers for commercial satellite up-links and point-to-multipoint wireless broadband "last mile" applications, where the low operating voltage is attractive due to reduced costs and increased reliability.

REFERENCES:
1. J.R. Legarra, et al., "A 500-W coupled-cavity TWT for Ka-band communication," IEEE Trans.on Electron Devices 52(5), May 2005.

2. K.T. Nguyen, et al., "Intense sheet electron beam transport in a uniform solenoidal magnetic field," IEEE Trans. on Electron Devices 56(5), May 2009.

3. R.L. Ives, et al., "Computational design of asymmetric electron beam devices," IEEE Trans. on Electron Devices 56(5), May 2009.

4. J.J. Petillo, et al., "The MICHELLE three-dimensional electron gun and modeling tool: theory and design," IEEE Trans. on Plasma Science 30(3), June 2002.

KEYWORDS: Electron beam; multiple beam; spatially distributed beam; millimeter-wave; vacuum electronics.

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between November 9 and December 11, 2011, you may talk directly with the Topic Authors to ask technical questions about the topics. Their contact information is listed above. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting December 12, 2011, when DoD begins accepting proposals for this solicitation.

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