Design of RF power coupler for superconducting cavities

Abstract

A new power coupler has been designed and is being prototyped by Argonne National Laboratory (ANL) for use with any of the ANL proposed superconducting (SC) half-or quarterwave cavities for SARAF [1] and Project-X [2]. The 50 Ohm coaxial capacitive coupler is required to operate in the CW regime with up to 15 kW of forward power and under any condition for the reflected power. A key feature is a moveable copper plated stainless steel bellows which will permit up to 3 cm of axial stroke and adjustment of the external quality factor by roughly one order of magnitude in the range of 10 5 to 10 6 . The mechanical and vacuum design includes two ceramic windows, one operating at room temperature and another at 70 Kelvin. The two window design allows the portion of the coupler assembled onto the SC cavity in the clean room to be compact and readily cleanable. Other design features include thermal intercepts to provide a large margin for RF heating and a mechanical guide assembly to operate cold and under vacuum with high reliability.

Energy recovery operation for continuous-wave X-ray free-electron lasers

“…( 4), it would be about 2.22 kW in 16 MV/m, while this value would be floating between 0.773 to 2.22 kW in normal operation, decided by the different beam loading. In full power ERL operation, the reflected power would be 6.8 kW in 27 MV/m, even though obviously stronger than normal mode, this value is still tolerable with the present coupler design due to the requirements to accommodate full input power reflection at any phase, and with the developments of more high average RF power couplers for superconducting cavities, 32,33 the capability of couplers to handle higher forward and reflected power could be further improved definitely.…”

Electromagnetic design of 402 MHz normal conducting coaxial window for SNS facility

“…These results are similar to those observed in the existing SNS HPW, where they are mitigated through RF conditioning. As mentioned earlier, the design of the coaxial window makes it possible to suppress the multipactor discharge by applying DC voltage bias between inner and outer conductors [2]. In the future, we plan to evaluate the value of the applying DC voltage to suppress the multipactor discharge or to evaluate the criticality of additional heating of ceramics caused by the multipactor discharge.…”

“…Modern accelerator facilities such as the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) [1], operate in a high-power pulsed regime and require reliable high-power RF components. One such component is the RF power coupler [2], which provides power delivery from the RF power source to the load. The critical part of the waveguide couplers is the RF window.…”

Suppression of multipacting in high power RF couplers operating with superconducting cavities

“…The full suppression of multipacting process in the capacitive RF couplers can be achieved by applying DC voltage into the antenna through the inner conductor of the coaxial line [3][4][5]. We have developed a DC bias insert (DC bias Tee) into the standard 3-1/8 coaxial transmission line as shown in Fig.…”