RF design of a single cell superconducting elliptical cavity with input coupler (original) (raw)
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IEEE Transactions on Applied Superconductivity, 2011
A coaxial power coupler for a superconducting multicell cavity resonator at 3.9 GHz has been developed. The cavity is intended to be employed as an accelerator to provide enhanced electron beam quality in a free-electron laser. Due to cryogenic high-vacuum and high-power requirements, special provisions for two windows and two bellows were implemented. A simulation tool was employed to optimize the coupler structure for low reflection of incident power and dissipation while restraining the field at critical locations to prevent material breakdown. The procedures for testing the coupler on its own and integrated with the superconducting cavity are described, and the measurement results are presented. The coupler-cavity assembly was tested to exceed the requirement of 9.3-kW input power and axial field intensity of 14.5 MV/m in the cavity. Coupler return and insertion losses were estimated to be 21 and 0.2 dB, respectively.
Electromagnetic Design of a $\beta_{g} = 0.9$ 650-MHz Superconducting-Radio-Frequency Cavity
IEEE Transactions on Applied Superconductivity, 2000
We present the electromagnetic design study of a multi cell, g = 0.9, 650 MHz elliptic superconducting radiofrequency cavity, which can be used for accelerating Hparticles in the linear accelerator part of a Spallation Neutron source. The design has been optimized for maximum achievable acceleration gradient by varying the geometry parameters of the cavity, for which a simple and general procedure is evolved that we describe in the paper. For the optimized geometry, we have studied the higher order modes supported by the cavity, and the threshold current for the excitation of the regenerative beam break up instability due to dipole modes has been estimated. Lorentz force detuning studies have also been performed for the optimized design and the calculations are presented to find the optimum location of the stiffener ring to compensate for the Lorentz force detuning.
Electromagnetic Design of a Superconducting Twin Axis Cavity
2017
The twin-axis cavity is a new kind of rf superconducting cavity that consists of two parallel beam pipes, which can accelerate or decelerate two spatially separated beams in the same cavity. This configuration is particularly effective for high-current beams with low-energy electrons that will be used for bunched beam cooling of high-energy protons or ions. The new cavity geometry was designed to create a uniform accelerating or decelerating fields for both beams by utilizing a TM110 dipole mode. This paper presents the design rf optimization of a 1497 MHz twin-axis single-cell cavity, which is currently under fabrication. INTRODUCTION The idea of utilizing elliptical shaped rf superconducting accelerating structures with two beam pipes intended for Energy Recovery Linacs (ERLs) applications was first proposed by Noguchi and Kako in 2003 [1]. A similar concept was revisited by Wang, Noonan, and Lewellen in 2007 [2, 3] and recently [4] for based ERL applications. The new proposed sup...
Design study on a superconducting multicell RF accelerating cavity for use in a linear collider
IEEE Transactions on Nuclear Science, 1998
A nine-cell superconducting RF accelerating cavity is designed for the TeV electron linear accelerator collider in the next century. The ratio of the maximum surface electric field to the accelerating gradient, E pk =E acc , is reduced to 2.024 and the cell-to-cell coupling remains as high as 1.95%. The distribution of the higher-order mode passbands is reasonable. There is no overlap between these bands, therefore no trapped modes. The circle-straight/line-ellipse-type structure provides good mechanical strength in the accelerating cavity. According to the present state of the art of surface processing techniques of Niobium cavities, it is possible to reach an accelerating gradient of 25-30 MV/m with beam load.
COUPLER DEVELOPMENT AND GAP FIELD ANALYSIS FOR THE 352 MHz SUPERCONDUCTING CH-CAVITY
The cross-bar H-type (CH) cavity is a multi-gap drift tube structure based on the H-210 mode currently under development at IAP Frankfurt and in collaboration with GSI. Numerical simulations and rf model measurements showed that the CH-type cavity is an excellent candidate to realize s.c. multi-cell structures ranging from the RFQ exit energy up to the injection energy into elliptical multi-cell cavities. A 19-cell, beta=0.1, 352 MHz, bulk niobium prototype cavity is under fabrication at the ACCEL-Company, Bergisch-Gladbach. This paper will present detailed MicroWave Studio [1] simulations and rf model measurements for the coupler development of the 352 MHz superconducting CHcavity. It describes possibilities for coupling into the superconducting CH-cavity. First results of the measurements of different coupler concepts, e.g. capacitive and inductive coupling at different positions of the CH-cavity are reported. Additionally the rf quadrupole content in CH-type gaps was investigated quantitatively.
Design of coupler for the NSLS-II storage ring superconducting RF cavity
2011
NSLS-II is a 3GeV, 500mA, high brightness, 1 MW beam power synchrotron facility that is designed with four superconducting cavities working at 499.68 MHz. To operate the cavities in over-damped coupling condition, an External Quality Factor (Qext) of ~ 65000 is required. We have modified the existing coupler for the CESR-B cavity which has a Qext of ~ 200,000 to meet the requirements of NSLS-II. CESR-B cavity has an aperture coupler with a coupler "tongue" connecting the cavity to the waveguide. We have optimized the length, width and thickness of the "tongue" as well as the width of the aperture to increase the coupling using the three dimensional electromagnetic field solver, HFSS. Several possible designs will be presented.
Prototyping of a Superconducting Elliptical Cavity for a Proton Linac
An L-band superconducting cavity has been designed for acceleration of particles travelling at 81% the speed of light (β = 0.81). Four single-cell prototypes have been being fabricated and tested. Two of these cavities were formed from standard high purity fine grain niobium sheet. The rest were fabricated from large grain niobium. The RF per- formance of the single-cell cavities indicate that the design is suitable for use in a proton linac; the highest measured accelerating gradient was about 28 MV/m. The fabrication of two 7-cell cavity prototypes is in progress.
A superconducting reentrant cavity for low beta, high intensity beam has been designed using SUPERFISH and MAFIA. The study has been done for cavity shape optimization. Further its structural design has been done and feasibility study of different manufacturing aspects has also been done. A full-scale mild steel model with copper coating has been fabricated. A twin arm mechanical tuner has been designed for slow tuning by elastic deformation. This was tested with low power RF to validate the design parameters and to check the tuning sensitivity. In this paper the design and development activity of the reentrant superconducting are discussed.