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Title: Input RF coupler design for energy compensator cavity in eRHIC

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Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
Report Number(s):
R&D Project: KBCH139; 18036; KB0202011
DOE Contract Number:
Resource Type:
Resource Relation:
Conference: 8th International Particle Accelerator Conference (IPAC17); Bella Center, Copenhagen, Denmark; 20170514 through 20170519
Country of Publication:
United States

Citation Formats

Xu C., Ben-Zvi, I., Blaskiewicz, M., Bellavia, S., Hao, Y., Smith, K., Than, R., and Zaltsman, A.. Input RF coupler design for energy compensator cavity in eRHIC. United States: N. p., 2017. Web.
Xu C., Ben-Zvi, I., Blaskiewicz, M., Bellavia, S., Hao, Y., Smith, K., Than, R., & Zaltsman, A.. Input RF coupler design for energy compensator cavity in eRHIC. United States.
Xu C., Ben-Zvi, I., Blaskiewicz, M., Bellavia, S., Hao, Y., Smith, K., Than, R., and Zaltsman, A.. 2017. "Input RF coupler design for energy compensator cavity in eRHIC". United States. doi:.
title = {Input RF coupler design for energy compensator cavity in eRHIC},
author = {Xu C. and Ben-Zvi, I. and Blaskiewicz, M. and Bellavia, S. and Hao, Y. and Smith, K. and Than, R. and Zaltsman, A.},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2017,
month = 5

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  • No abstract prepared.
  • The current design of the Accelerator Driven Test Facility (ADTF) accelerator contains multiple {beta}, superconducting, resonant cavities. Spoke-type resonators ({beta} = 0.175 and {beta} = 0.34) are proposed for the low energy linac immediately following the radio frequency quadrupole. A continuous wave power requirement of 8.5 - 211.8 kW, 350 MHz has been established for the input couplers of these spoke cavities. The coupler design approach was to have a single input coupler design for beam currents of 13.3 mA and 100 mA and both cavity {beta}'s. The baseline design consists of a half-height WR2300 waveguide section merged with amore » shorted coaxial conductor. At the transition is a 4.8-mm thick cylindrical ceramic window creating the air/vacuum barrier. The coax is 103-mm inner diameter, 75 Ohm. The coax extends from the short through the waveguide and terminates with an antenna tip in the sidewall of the cavity. A full diameter pumping port is located in the quarter-wave stub to facilitate good vacuum. The coaxial geometry chosen was based on multipacting and thermal design considerations. The coupling coefficient is adjusted by statically adjusting the outer conductor length. The RF-physics, thermal, vacuum, and structural design considerations will be discussed in this paper, in addition to future room temperature testing plans.« less
  • A variable input coupler has been designed for the Fermilab vertical cavity test facility (VCTF), a facility for CW RF vertical testing of bare ILC 1.3 GHz 9-cell SRF cavities at 2K, to provide some flexibility in the test stand RF measurements. The variable coupler allows the cavity to be critically coupled for all RF tests, including all TM010 passband modes, which will simplify or make possible the measurement of those modes with very low end-cell fields, e.g., {pi}/9 mode. The variable coupler assembly mounts to the standard input coupler port on the cavity, and uses a cryogenic motor submergedmore » in superfluid helium to control the antenna position. The RF and mechanical design and RF test results are described.« less
  • A high current five-cell Nb superconducting cavity, called BNL3 cavity, was optimized and designed for the SPL and eRHIC. For the fundamental mode, the optimization process aimed at maximizing the R/Q of the fundamental mode and the geometry factor G under an acceptable RF field ratio level of B{sub peak}/E{sub acc} and E{sub peak}/E{sub acc}. For higher order modes, the optimization is to lower (R/Q)Q{sub ext} for dipole and quadrupole modes to suppress the beam-break-up (BBU). To extract the HOM power out of the cavity, the BNL3 cavity employs a larger beam pipe, allowing the propagation of HOMs, but notmore » the fundamental mode. Six HOM couplers (three at each end) are used to extract large HOM power. To avoid the cross-talk between cavities, tapers are employed between the cavities. This paper presents the design of the BNL3 cavity, end groups and BBU simulation results.« less
  • To prevent significant loss of the luminosity due to large crossing angle in the future ERL based Electron Ion Collider at BNL (eRHIC), there is a demand for crab cavities. In this article, we will present a novel design of the deflecting/crabbing 181 MHz superconducting RF cavity that will fulfil the requirements of eRHIC. The quarter-wave resonator structure of the new cavity possesses many advantages, such as compact size, high R{sub t}/Q, the absence of the same order mode and lower order mode, and easy higher order mode damping. We will present the properties and characteristics of the new cavitymore » in detail. As the accelerator systems grow in complexity, developing compact and efficient deflecting cavities is of great interest. Such cavities will benefit situations where the beam line space is limited. The future linac-ring type electron-ion collider requires implementation of a crab-crossing scheme for both beams at the interaction region. The ion beam has a long bunches and high rigidity. Therefore, it requires a low frequency, large kicking angle deflector. The frequency of the deflecting mode for the current collider design is 181 MHz, and the deflecting angle is {approx}5 mrad for each beam. At such low frequency, the previous designs of the crab cavities will have very large dimensions, and also will be confronted by typical problems of damping the Lower Order Mode (LOM), the Same Order Mode (SOM), and as usual, the Higher Order Modes (HOM). In this paper we describe how one can use the concept of a quarter-wave (QW) resonator for a deflecting/crabbing cavity, and use its fundamental mode to deflect the beam. The simplicity of the cavity geometry and the large separation between its fundamental mode and the first HOM make it very attractive.« less