[Show abstract][Hide abstract] ABSTRACT: Fundamental power couplers are critically important components in all superconducting accelerators. Power couplers provide the vacuum and thermal interface between the superconducting cavity and the room temperature waveguide components and transmit microwaves generated by the high power microwave source. Power couplers must be extraordinarily clean and reliable to ensure that they meet the stringent requirements associated with superconducting accelerators. CPI power couplers are manufactured to our customer's specifications using processes which are standard to the vacuum electron device industry as well as processes which are specific to power couplers. To meet our customer's requirements, we have developed the capability of plating high residual resistivity ratio (RRR) copper on stainless steel. Plating is done in-house under carefully controlled conditions. Our high-RRR-copper plating has been qualified by CNRS-Orsay and Cornell. We have developed the capability of applying TiN coatings to ceramic windows. TiN coating is done in- house under carefully controlled conditions. Our TiN coating process has been qualified at DESY. Using these processes, CPI has manufactured over 50 power couplers of various designs. This year we will manufacture an additional 50 power couplers. This paper will focus on power couplers for the International Linear Collider (ILC). In particular, we will discuss some of the challenges to be faced during the manufacture of tens of thousands of power couplers for the ILC. These challenges were identified during our recent cost study for the ILC RF unit.
[Show abstract][Hide abstract] ABSTRACT: More and more accelerators are built with superconducting cavities operating at cryogenic temperatures. A possible window failure might result in contamination of the cavity surface and degrade the accelerating performance. A cost effective design and fabrication method for a new coupler has been developed by AMAC. This new design is an alternative to the present TESLA cylindrical ceramic windows layout. The new design includes two planar disc windows separated by a vacuum space. An alternative design option proposes filling dry nitrogen gas in between the two ceramic windows. Furthermore the new design is optimized for RF input power, taking into consideration the possible requirements of the TESLA superstructure layout. Two prototype couplers with this design have been fabricated. The couplers are being tested on the high power test stand at DESY, Germany. This paper describes the new coupler design and discusses the first measured results.
[Show abstract][Hide abstract] ABSTRACT: The Rare Isotope Accelerator uses 805 MHz superconducting rf cavities in the linac. Power is transmitted capacitively into the cavities via a high power input coupler. The coupler was designed for greater than 10 kW cw with a VSWR less than 1.05. The design load to the 2 K liquid helium is less than 2 W. The external Q of the coupler is about 2×10<sup>7</sup>. The couplers were conditioned off-line to over 200 kW pulsed before installation into a prototype cryomodule. The cryomodule was tested at 2 K to full accelerating gradients. Multipacting barriers in the coupler were quickly conditioned, and no arcs or discharges were observed during testing. Details of the power couplers performance will be presented.
[Show abstract][Hide abstract] ABSTRACT: More and more accelerators are built with superconducting cavities operating at cryogenic temperatures, and the probability of a ceramic window failure presents increasing problems because of the resulting contamination of the cavities’ surfaces and the resulting accelerating electric field degradation. Double ceramic window couplers are required to reduce this risk. The TESLA superstructure cavity requires a new coupler for the higher power input and the coupling characteristics. A cost effective design and fabrication method for these couplers has been developed to meet these demands. This new design presents an alternative to the present TESLA cylindrical ceramic windows, uses two planar disc windows separated by a vacuum space, and is optimized for RF input power, vacuum characteristics, and thermal properties. Two couplers with this design have been fabricated and are presently being tested at DESY, Germany on the RF high power testing stand and will also be tested on a test cryomodule. The design will be discussed in this paper.
[Show abstract][Hide abstract] ABSTRACT: In this paper, design, fabrication and cold test of window couplers are discussed. The SNS prototype window couplers contain an alumina disk window and a water cooled center conductor. Standard microwave tube industry fabrication procedures were used to assemble the window coupler. These window couplers utilize a unique compression ring technology.
Vacuum Electronics, 2003 4th IEEE International Conference on; 06/2003
[Show abstract][Hide abstract] ABSTRACT: A novel high power RF coupler was developed and designed by AMAC to reliably operate at an average power level over 200 kW and to exceed the present specification requirements for the SNS accelerator project. CPI performed the manufacturing optimization and the fabrication of prototypes. The RF couplers were conditioned and tested at the Jefferson Laboratory. An innovative feature consisting of a compression ring was incorporated to reduce the tensile forces on the ceramic by pre -stressing the ceramic and increase the reliability of the ceramic window. Watercooling is used to remove the dissipated power at the window and the antenna. Extensive calculations were performed to optimize window design using MAFIA, HFSS, ANSYS, multipacting program. Based on the above efforts, an innovative RF surfaces design (AMAC-2) was developed to remove the chocks used in AMAC-1 and provided the following advantages: better vacuum, easier cleaning, and less secondary electron-multipacting. The simulation, design consideration, engineering design and results of the RF high power qualification were briefly discussed in this paper.
[Show abstract][Hide abstract] ABSTRACT: The RF coupler was designed by AMAC to meet the specification requirements for the SNS accelerator project. CPI performed the manufacturing optimization. AMAC as primary contractor was awarded a contract by Jefferson lab to provide three SNS prototype coupler windows using AMAC-1 window assembly design. CPI performed the fabrication. Three AMAC-1 prototypes have been high RF power tested and qualified to SNS technical specifications by J efferson Lab. This paper mainly focuses on the design optimization, key simulation results of HFSS, MAFIA, ANSYS, electron-multipacting program results, and the mechanical design features as well. The fabrication and the cold test are described in a separate presentation in this workshop.
[Show abstract][Hide abstract] ABSTRACT: The RIA RF high power coupler window was designed by AMAC to meet the specification requirements for the RIA accelerator project, and is based on AMAC's SNS RF coupler window design. MSU provided the RF specification, and performed the calculations to match the coupler to the SRF cavity. CPI performed the manufacturing optimization, and fabricated two prototype couplers. The prototypes have been high RF power tested by the Jefferson Lab and met or exceeded the requirements of the RIA technical specifications. The RF tests and conditioning are described in a separate presentation in this workshop. AMAC was awarded a contract to provide two prototype RIA RF input power coupler windows in a very short period, and for this reason it was decided to base the design on the proven SNS AMAC-1 coupler . The main changes were the modification of the antenna and the removal of the water cooling feature. The water is not required due to the lower required RF power level of 10kW CW. Two window couplers were delivered; high RF power tested, and qualified to meet the RIA technical requirements. The RIA technical requirement are briefly listed in the following: VSWR: 1.05 or lower at 805 MHz Maximum radiative heat loss to 2.1K circuit: 1 W Maximum CW power: 10 kW External Q of coupler: 2 x 10 -7 Operating pressure: <5 × 10 -9 torr Radiation resistance at tip of antenna: 4 × 10 8 rads DESCRIPTION It is is a coaxial type of coupler with a planar ceramic window separating the vacuum side from air side. In the HFSS simulation, the loss tangent is taken as 0.0002, and the permittivity value is 9.6. The RIA accelerating cavity geometry requires a coaxial 805 MHz coupler design with a transition to a standard 3-1/8" transmission line. The window geometry incorporates chokes at the inner and outer conductor. The dissipated power at the window and the antenna are transferred conductively thru the material and removed by air cooling The vacuum side of the ceramic window is coated with 20-25 Angstrom Titanium Nitride. Figures 1a and 1b show the general assembly drawing and a photo the coupler window.
[Show abstract][Hide abstract] ABSTRACT: Communications & Power Industries, Inc. (CPI) has active programs to refine key components for the European XFEL. These components, the fundamental power coupler and the multibeam klystron (MBK) are also suited for the International Linear Collider (ILC). CPI power couplers are manufactured to our customer's specifications using processes which are standard to the electron device industry as well as processes which are specific to power couplers. We have developed the capability of plating high-RRR copper on stainless steel. We have developed the capability of applying TiN coatings to ceramic windows. Both processes are done in-house under carefully controlled conditions. Both processes have been fully qualified. CPI has manufactured over 100 power couplers of various designs. Our presentation will focus on power couplers for the XFEL and the ILC. CPI is currently developing a second-generation, horizontal MBK for DESY. This MBK operates at 10 MW, at an RF frequency of 1.3 GHz, 1.5 ms pulse length, and 10 Hz pulse repetition rate. Our presentation will provide an update on this development program.