High Power RF Window and Its Input Coupler Technology

AMAC International, Inc.

12050 Jefferson Avenue

ARC, Suite 348

Newport News, VA 23606-4385

PI: Dr. Quan-Sheng Shu

DOE Grant No: DE-FG02-99ER82739

Technology: Innovative high reliability, very high power RF window and corresponding input coupler design concepts were developed and optimized by using advanced computer programs to meet the strong demands of various accelerator projects. The novel design concepts incorporate the compression ring and internal cooling technologies and optimized RF surface shapes into the window design to enhance the reliability of the RF window. Up to five input coupler prototypes, including two waveguide type modules and three coaxial modules, have been fabricated and successfully high power tested and all designs meet the SNS project requirements, with the support and collaboration of Communications & Power Industries, Inc.(CPI) and DOE Jefferson Lab.

Benefits: The reliability and cost effectiveness of very high CW power RF windows and couplers are critical to the performance and future development of new accelerators in nuclear physics, high energy physics, Free Electron Laser (FEL) and nuclear industries. The RF input window and couplers in superconducting cavities must operate through various power levels and RF loads of complex impedances without arcing, overheating, or non-uniform mechanical stress failures. High power demand for high RF power applications are constantly increasing. By using a compression ring and internal cooling jacket in the RF window design, the thermal stress level in the window will be noticeably lowered so that the fatigue life of the window is improved. The novel individually processing window coupler system developed in this project will reduce the post-processing time and cost. AMAC’s success in the DOE SBIR project makes it possible for the first time for an American company to win a high RF power window contract (SNS) in an international competition.

Applications: High RF power input couplers are essential components, which transfer the RF wave power from the RF power source (Klystron, room temperature) to superconducting cavities (liquid helium temperature) of an accelerator. The innovations of reliable, low cost window couplers can be used in every RF tube window design/fabrication, in every high RF power input coupler of all the accelerator projects world-wide such as: SNS, Jefferson Lab upgrade, FEL, Muon Collider, energy amplifier, radioactive waste treatment, synchrotron radiation, and TESLA. Novel processing technologies developed in this project can also be used in Gyrotron windows and other vacuum joints of dissimilar materials.

Benefit to the Company: AMAC International, Inc. is a high tech company operating at the cutting edge of a broad band of high technologies including: Superconducting Radio Frequency (SRF) cavities pertinent technology, superconductivity, cryogenics, etc.. AMAC has previously received a total of $850,000 SBIR funds from The US Department of Energy (DOE). Based on AMAC’s successes on SBIR projects, in 2001 AMAC was awarded by DOE a $500,000 STTR Phase II award to develop innovative high power Radio Frequency (RF) window and coupler technology. The successes in winning SBIR awards have greatly thrust the development of the whole company in the direction of high-tech R&D:

· AMAC hired two PhD engineers by part of SBIR project funding.

· In a strong international competition, AMAC (the first US company ever) and Toshiba ( Japan ) are the only two companies that won the SNS contract to build three SNS input coupler prototypes and successfully qualified to all the SNS technical requirements.

· The AMAC input coupler techniques have been licensed to CPI (the largest RF products manufacturer in the US ), for their further marketing and development. The royalty from licensing is 8%. For a contract worth 3 million dollars, AMAC will gain $ 240,000.

· Two patent applications are planning to be submitted.

· AMAC’s successes in winning DOE SBIR awards have been reported in primary Virginia newspapers including Virginia Pilot, Inside Business, Daily Press, etc..

· Virginia Commonwealth state government has issued AMAC a “Outstanding Achievement Award” certificate as acknowledgement of AMAC’s success in DOE SBIR projects.

Acknowledgement: AMAC sincerely appreciates the support from the DOE Jefferson Lab ( Newport News , VA ) through a CRADA between Jefferson Lab and AMAC in high RF power testing of the high RF power windows and couplers. AMAC also thanks the Communications Power Industries, Inc. (CPI) for their in-kind support of $150,000 to the project and fabrication of the prototypes.

(a) Waveguide input couplers

(b) High RF Power Test Fixture of AMAC’s RF Waveguide Window

(d) AMAC’s window-coupler in high RF power (2.0MW) testing

Fig. 1 AMAC’s high RF power input couplers and test fixtures used in SBIR projects

Fig. 2 Newspaper articles about AMAC’s achievements in DOE SBIR projects and the honor certificate issued to AMAC by Virginia Commonwealth state government