Multipactor simulations in superconducting cavities

Gonin, I.; Solyak, N.; DeFord, J.F.; Held, Ben

doi:10.1109/pac.2007.4441212

Cited by 6 publications

(9 citation statements)

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“…This section discusses theory predictions for wakefields in the six cell PBG structure. Direct wakefield calculations have been made using the STAAR code ANA-LYST [18,19]. Eigenmode calculations using HFSS have also been used to understand HOMs in PBG structures.…”

Section: Theory and Cold Testmentioning

confidence: 99%

“…A PBG lattice is formed by a triangular lattice of cylindrical metallic rods; one rod is removed from the center to form a defect which confines the T M 01 operating mode. Dimensions for labels are given in Table 1. package developed by Simulation Technology & Applied Research (STAAR) [18,19]. For this work the time-domain field modeling component of ANALYST (called TD3P) was used.…”

Section: Front Viewmentioning

confidence: 99%

“…In order to predict the power lost by the beam into the structure, HFSS simulations were performed to probe the properties of various PBG HOMs, after [17]. Time domain simulations were also performed to calculate directly the wakefields excited by a bunch train transiting the structure using the STAAR code ANALYST [18,19].…”

Section: Introductionmentioning

confidence: 99%

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Measurement of wakefields in a 17GHz photonic bandgap accelerator structure

Marsh¹,

Shapiro²,

Temkin³

et al. 2010

Nuclear Instruments and Methods in Physics Research Section A:

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We report the experimental measurement of wakefields in a 17.14 GHz metallic photonic bandgap accelerator structure and its comparison with theory. Damping of wakefields is a critical issue in the next generation of high gradient electron accelerators, and photonic bandgap (PBG) structures have unique properties for suppressing and damping wakefields. In the experiments the wakefields were generated by passing an 18 MeV electron beam through the six cell 17.14 GHz structure. The wakefield radiation was measured at two locations: the structure output port, and at a window viewing port located at the side of the structure. The electron beam consisted of a train of bunches spaced at 17.14 GHz, so that only radiation at 17.14 GHz and its harmonics was observed. Wakefields at up to the fifth harmonic (85.7 GHz) were detected by a heterodyne receiver system. The wakefield power levels were measured at 17 and 34 GHz for average currents between 20 and 300 mA. The results were compared with full wakefield simulations using the code ANALYST. The measured power level at 17 GHz was in excellent agreement with the theoretical estimate, but the measured power at 34 GHz was significantly lower than the theoretical estimate. At both 17 and 34 GHz the measured power level increased as the beam current squared, as expected from theory. The experimental results demonstrate the weak excitation of high order mode wakefields in a photonic bandgap structure.

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Section: Theory and Cold Testmentioning

confidence: 99%

Section: Front Viewmentioning

confidence: 99%

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Measurement of wakefields in a 17GHz photonic bandgap accelerator structure

Marsh¹,

Shapiro²,

Temkin³

et al. 2010

Nuclear Instruments and Methods in Physics Research Section A:

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“…Figure 4 shows an example of MP in HOM coupler of 3.9 GHz cavity [7]. Aggressive high power processing caused damaging of both couplers.…”

Section: Multipactor (Mp)mentioning

confidence: 99%

Gradient Limitations in Room Temperature and Superconducting Acceleration Structures

Solyak¹

2009

AIP Conference Proceedings

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Abstract. Accelerating gradient is a key parameter of the accelerating structure in large linac facilities, like future Linear Collider. In room temperature accelerating structures the gradient is limited mostly by breakdown phenomena, caused by high surface electric fields or pulse surface heating. High power processing is a necessary procedure to clean surface and improve the gradient. In the best tested X-band structures the achieved gradient is exceed 100 MV/m in of ~200 ns pulses for breakdown rate of ~10 -7 . Gradient limit depends on number of factors and no one theory which can explain all sets of experimental results and predict gradient in new accelerating structure. In paper we briefly overview the recent experimental results of breakdown studies, progress in understanding of gradient limitations and scaling laws. Although superconducting rf technology has been adopted throughout the world for ILC, it has frequently been difficult to reach the predicted performance in these structures due to a number of factors: multipactoring, field emission, Q-slope, thermal breakdown. In paper we are discussing all these phenomena and the ways to increase accelerating gradient in SC cavity, which are a part of worldwide R&D program.

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“…Multipacting analysis of the HOM coupler predicts two MP zones. The first one is located in the tuning gap at Eacc=1.5MV/m, and the second one is wider and stronger at Eacc = 12-19 MV/m [1][2][3].…”

Section: Problems With Homsmentioning

confidence: 99%

New hom coupler design for 3.9 GHZ superconducting cavities at FNAL

Khabiboulline

Gonin

Solyak

2007

2007 IEEE Particle Accelerator Conference (PAC)

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Over the last few years Fermilab has developed the superconducting third harmonic section for t he FLASH (TTF/DESY) upgrade. Initial v ertical tests of 9 -cell Nb cavities didn't reach the designed accelerating gradient. The main factor of gradient limitation was multipacting in the HOM coupler. In this paper we present the results of vertical tests ac companied with 3D analysis simulations of multipacting. Also we discuss the RF design of the new HOM couplers. The goal of the new design is to eliminate multipacting and to increase the second resonance frequency of the HOM coupler . Increasing this frequency reduces electric and magnetic fields , resulting in decreased thermal load on the antenna. Two cavities with modified HOM couplers have achieved operating gradients of 23MV/m.

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Multipactor simulations in superconducting cavities

Cited by 6 publications

References 0 publications

Measurement of wakefields in a 17GHz photonic bandgap accelerator structure

Measurement of wakefields in a 17GHz photonic bandgap accelerator structure

Gradient Limitations in Room Temperature and Superconducting Acceleration Structures

New hom coupler design for 3.9 GHZ superconducting cavities at FNAL

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