Purpose Higher-order modes(HOMs)may affect beam stability and refrigeration requirements of superconducting cavity such as the 166.6MHz SC cavity,which is studied at IHEP.Under certain conditions,beam-induced HOMs can...Purpose Higher-order modes(HOMs)may affect beam stability and refrigeration requirements of superconducting cavity such as the 166.6MHz SC cavity,which is studied at IHEP.Under certain conditions,beam-induced HOMs can accumulate sufficient energy to destabilize the beam or quench the superconducting cavities.Methods In order to limit these effects,we consider the use of the HOM coupler with HOMs extraction on the cutoff tubes of the 166.6MHz SC cavity.Results The HOM coupler can deeply suppress the fundamental mode and efficiently extract dangerous high-order modes.Conclusions In this paper,the HOM coupler design process is presented,which operates at 166.6MHz.The RF and thermal behavior are discussed.In order to verify the designs,a rapid prototype for the favored couplerwas fabricated and characterized on a low-power test stand.展开更多
Purpose The 166.6 MHz superconducting radio frequency cavities have been proposed for High Energy Photon Source(HEPS)storage ring.HEPS is a 6 GeV,200 mA diffraction-limited synchrotron light source to be built in Beij...Purpose The 166.6 MHz superconducting radio frequency cavities have been proposed for High Energy Photon Source(HEPS)storage ring.HEPS is a 6 GeV,200 mA diffraction-limited synchrotron light source to be built in Beijing.Higherorder modes(HOMs)excited in 166.6 MHz SRF cavities have to be sufficiently damped in order to prevent coupled-bunch instabilities and to limit parasitic mode losses.Methods A hybrid HOM damping scheme has been proposed.An enlarged beam pipe allows HOMs above beam pipe cutoff frequencies to propagate and subsequently be absorbed by dampers installed on the downstream beam pipe,while a petal-shaped coaxial structure extracts HOMs below beam pipe cutoff frequencies and subsequently damped by the specially designed coaxial filter.Results HOMdamping in cavities has been demonstrated by 3D simulations.The impedance of HOMs has been successfully reduced to be lower than the coupled-bunch instability threshold.In addition,no hard barrier multipaction has been observed and acceptable heat loss is obtained.Conclusions In this paper,the hybrid HOM damping scheme has been demonstrated.Based on these studies,a prototype petal–loop structure and its associated filter are being fabricated.展开更多
文摘Purpose Higher-order modes(HOMs)may affect beam stability and refrigeration requirements of superconducting cavity such as the 166.6MHz SC cavity,which is studied at IHEP.Under certain conditions,beam-induced HOMs can accumulate sufficient energy to destabilize the beam or quench the superconducting cavities.Methods In order to limit these effects,we consider the use of the HOM coupler with HOMs extraction on the cutoff tubes of the 166.6MHz SC cavity.Results The HOM coupler can deeply suppress the fundamental mode and efficiently extract dangerous high-order modes.Conclusions In this paper,the HOM coupler design process is presented,which operates at 166.6MHz.The RF and thermal behavior are discussed.In order to verify the designs,a rapid prototype for the favored couplerwas fabricated and characterized on a low-power test stand.
文摘Purpose The 166.6 MHz superconducting radio frequency cavities have been proposed for High Energy Photon Source(HEPS)storage ring.HEPS is a 6 GeV,200 mA diffraction-limited synchrotron light source to be built in Beijing.Higherorder modes(HOMs)excited in 166.6 MHz SRF cavities have to be sufficiently damped in order to prevent coupled-bunch instabilities and to limit parasitic mode losses.Methods A hybrid HOM damping scheme has been proposed.An enlarged beam pipe allows HOMs above beam pipe cutoff frequencies to propagate and subsequently be absorbed by dampers installed on the downstream beam pipe,while a petal-shaped coaxial structure extracts HOMs below beam pipe cutoff frequencies and subsequently damped by the specially designed coaxial filter.Results HOMdamping in cavities has been demonstrated by 3D simulations.The impedance of HOMs has been successfully reduced to be lower than the coupled-bunch instability threshold.In addition,no hard barrier multipaction has been observed and acceptable heat loss is obtained.Conclusions In this paper,the hybrid HOM damping scheme has been demonstrated.Based on these studies,a prototype petal–loop structure and its associated filter are being fabricated.
