TECHNOLOGY AREAS: Ground/Sea Vehicles, Weapons

ACQUISITION PROGRAM: PMS 405

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: To develop the manufacturing methodology and techniques for the production of high-quantum-efficiency photocathode devices that meet Free Electron Laser (FEL) weapon performance requirements and affordability criteria. This will require the transition from table-top, one of a kind construction to well defined fabrication procedures.

DESCRIPTION: Free Electron Lasers (FELs) are the present high-power directed energy weapon (DEW) of choice for the Navy. Effective FEL weapon injectors require high-average-current photocathodes that deliver CW average Ampere-level currents. These cathodes must be robust and stable with lifetimes exceeding 100 Amp-hours. Weapon system cathodes must consistently produce > 5% quantum efficiency (QE) with green illumination for the entire cathode lifetime. Current density and pulse format are also important parameters for these devices. A cathode that has high current density and can be gated at high frequency enables greater flexibility and enhanced performance. Present fabrication techniques are inadequate to deliver the required specifications. Hence affordable cathodes (as defined by the capital and operational cost of the associated photocathode drive laser system and the operational cost associated with cathode lifetime, performance, reliability and replacement) do not presently exist for FEL weapons. The objective of the present program is to rectify this shortfall in performance and affordability. Ultimately, the final choice of cathode technology may well depend upon its manufacturability.

PHASE I: Under Phase I of the SBIR the contractor shall:
- select one or more high-quantum-efficiency cathode technologies for study.
(Concepts could include but are not limited to multi-alkali cathode materials, dispenser and diamond amplifier devices, as well as GaAs and GaN semiconductors.)
- conduct an investigation to determine the feasibility of reliable production of the selected cathode(s) and justify how the required performance and affordability will be achieved.
- develop a preliminary process flow and fabrication plans.

PHASE II: Under Phase II the contractor shall:
- produce prototype cathodes and evaluate them for reliability.
- demonstrate performance consistent with cathode performance requirements and affordability criteria.
- fully develop and demonstrate a reliable and robust fabrication procedure.

PHASE III: Under a Phase III program, the contract shall:
- manufacture cathodes for integrated electron injector system evaluation.
- specifically, cathodes shall be capable of insertion into an operational high-current electron source to demonstrate consistent achievement of required performance and lifetime specifications.
- demonstrate that the manufacturing processes developed and performance achieved meet the defined affordability criteria.
Access to a suitable electron injector will be provided as GFE to the contractor by the Navy FEL Innovative Naval Prototype Program.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: High-QE photocathodes are equally sought after in the private sector.
Photocathode electron injectors can be found in numerous Universities and R&D Institutions worldwide. An affordable, higher performance photocathode concept would find immediate application as a replacement cathode at all these institutions. Specific high impact examples include the many light sources (40 intense synchrotron light sources worldwide) that are used for commercial development and the next generation of energy recovery linac (ERL) light sources that are presently on the drawing boards.
In a more speculative context, if the cost can be driven low enough and the quantum efficiency high enough (>20%) then the manufactured device might be suitable for use in photomultiplier tubes which represent a very large commercial market. One cathode concept has been suggested as the source for a so-called "lasertron" which can be considered as an Inductive Output Tube (IOT) with very high efficiency. Carrying this concept further, one can envision operating such a high-current density, high-gain cathode in a thermionic mode at which point the applicability within the enormous vacuum electronic tube industry opens up. Not only would improved vacuum electronic tubes benefit the broadcasting and transportation industries (via radar systems) but would come full circle to again benefit DOD where they are widely used.

REFERENCES:
1. Kevin L. Jensen, Donald W. Feldman, Nathan A. Moody, and Patrick G. O'Shea, "A Photoemission Model for Low Work Function Coated Metal Surfaces and Its Experimental Validation," J. Appl. Phys. 99, 124905 (2006).

2. X.Y. Chang, I. Ben-Zvi, A. Burrill, P.D.J. Johnson, J. Kewisch, T. Rao, Z. Segalov, Y. Zhao, "Study of Secondary Emission Enhanced Photoinjector", http://accelconf.web.cern.ch/accelconf/p05/PAPERS/TPPE042.PDF

3. Norton, T. J., Woodgate, B. E., Stock, J., Hilton, G., Ulmer, M. P., Aslam, S., Vispute, R. D. "Results from Cs activated GaN photocathode development for MCP detector systems at NASA GSFC" Proc. of SPIE, 5164, 155 (2003).

4. Brookhaven National Laboratory (United States Patent Application 20070181833 Kind Code A1 Srinivasan-Rao; Triveni ; et al. August 9, 2007).
KEYWORDS: Photocathode; High-Quantum-Efficiency; Long Lifetime; High-Current-Density; Free Electron Laser; Electron Injector

** TOPIC AUTHOR (TPOC) **

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