N102-190 TITLE: Multipaction Mitigation

TECHNOLOGY AREAS: Information Systems, Sensors, Electronics, Space Platforms

ACQUISITION PROGRAM: Mobile User Objective System (MUOS), ACAT I

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: Develop new passive and active multipaction mitigation technologies that can be incorporated into conventional and advanced satellite communication system payloads.

DESCRIPTION: Multipaction, or multiple impaction, is an electron resonance effect that occurs when Radio Frequency (RF) fields accelerate electrons in a vacuum and cause them to impact a surface releasing one or more electrons into the vacuum. These electrons can then be accelerated and impact the same or another surface. When the impact energies, number of electrons released, and timing of the impacts results in a sustained multiplication of a number of electrons, the phenomenon grows exponentially resulting in operational impairments and potentially physical damage.

In RF space systems, multipaction can cause loss and distortion of the RF signal (increase of noise figure or bit-error-rate) and can damage RF components or subsystems due to excess RF power being reflected back or dissipated by them.

Design rules, RF design tools such as the European Space Agency�s Multipactor Calculator, and test methods provide ways to achieve design margins that preclude the onset of multipaction. However, these approaches can result in restrictive device geometries and reduce RF power levels.

The development of new passive and active multipaction mitigation technologies that can be incorporated into conventional and advanced satellite communication system payload designs could potentially allow multipaction free operation of more compact device geometries and higher RF power levels.

Passive multipaction mitigation technologies might take the form of coatings or other surface treatments that inhibit the release of electrons from potential multipaction generating impacts while retaining the desired spacecraft surface properties of emissivity and thermal conductivity.

Active multipaction mitigation technologies might take the form of steady or slowly varying magnetic fields used to inhibit or disrupt the onset of multipaction. Since the force experienced by a charge moving in a magnetic field is perpendicular to its velocity vector ( F = V x B), charges being accelerated by an RF field toward a surface can be deflected to travel in circular or spiral paths avoiding surface impacts and the generation of secondary electrons required for multipaction phenomenon to occur.

PHASE I: Develop a new passive and/or active multipaction mitigation technology concept(s) with analytical or numerical calculations to establish performance possibilities. Translate design concepts into a product development roadmap establishing a technical and program pathway to an operational capability demonstration.

Tasks under this phase could include:
� Develop new passive and/or active multipaction mitigation technology concepts
� Predict performance parameters for multipaction mitigation technologies
� Produce a point design for demonstration test articles

PHASE II: Produce and test developmental test articles incorporating the multipaction mitigation technologies in a thermal vacuum test environment
� Implement the new design or process
� Evaluate measured performance characteristics versus expectations and make design/process adjustments as necessary.

PHASE III: This phase will focus on the integration of multipaction mitigation technologies with military satellite systems under development, such as the successor to the Mobile User Objective System (MUOS).

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Nearly every commercial satellite or space system has an RF communication payload that could benefit from multipaction mitigation.

REFERENCES:
1. "Multipaction," Wikipedia article, available at http://en.wikipedia.org/wiki/Multipaction, [Accessed 02 December 2009]

2. "Multipaction," encyclopedia article, available at: http://www.microwaves101.com/encyclopedia/multipaction.cfm [Accessed 02 December 2009]

3. "Multipactor Calculator Version 1.61 (April 2007)," European Space Agency, Available at: http://multipactor.esa.int

4. "RF Breakdown Characterization," Public Lessons Learned Entry: 0770, NASA Engineering Network, Available at: http://www.nasa.gov/offices/oce/llis/0770.html [Accessed 02 December 2009]

5. Udiljak, R., D. Anderson, U. Jostell, M. Lisak, J. Puech, V.E. Semenov, "Detection of Multicarrier Multipaction using RF Power Modulation," 4th International Workshop on Multipactor, Corona, and Passive Intermodulation in Space RF Hardware, Noordwijk, The Netherlands, 8-11 September 2003. Available at: http://conferences.esa.int/03C26/ [Accessed 15 December 2009]

6. ESA for ECSS, Space Engineering: Multipaction design and test, ESA Publications Division, The Netherlands, ECSS-E-20-01a, 5 May 2003.

7. A.J. Marrison, R. May, J.D. Sanders, A.D. Dyne, A.D. Rawlins, and J. Petit, A Study of Multipaction in Multicarrier RF Components, AEA Technology for ESTEC, AEA Ref. No. AEA/TYKB/31761/01/RP/05 Issue 1, Culham , UK, January 1997.

8. V. Semenov, A. Kryazhev, D. Anderson, and M. Lisak, "Multipactor suppression in amplitude modulated radio frequency fields," Phys. Plasmas, Vol. 8, No. 11, pp. 5034-5039, November 2001.

9. R. Udiljak, D. Anderson, P. Ingvarson, U. Jordan, U. Jostell, G. Li, M. Lisak, L. Lapierre, J. Puech, and J. Sombrin, "New Method for Detection of Multipaction," IEEE Trans. Plasma Sci., Vol. 31, No. 3, pp. 396-404, June 2003.

10. R. Kishek, Y.Y. Lau, and R. Gilgenhach, "Temporal Evolution of Multipactor Discharge," Proc. 1995 Particle Accelerator, Conf., Vol. 3, pp. 159-1601, May 1995.

11. US Patent 7623004, "Method and Structure for Inhibiting Multipactor, Issued November 24, 2009.

KEYWORDS: multipaction; impaction; resonance; RF; communications; vacuum

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