Double Cell Notch Filter for SRF Gun Investigations

Some projects of SRF guns apply the design where the cathode can be easily and quickly removed. One of the disadvantages of this design is the RF power leakage from the accelerating gun cavity cells to the cathode housing that result in the excessive cathode heating. To minimize the RF power leak different kinds of choke filters are used to protect the cathode structure. These choke filters represent resonant circuits with zero input impedance and installed at the entrance of the cathode structure that shunt the cathode housing. Still, since the choke filter frequency shift under working conditions is bigger than its bandwidth a filter tuning during assembly only in the warm stage seems insufficient and requires also fine tuning during operation. To eliminate the problems of the choke filter finetuning and hence ensure its stability during operation, a combination of the resonance choke elements can be implemented. In the paper we demonstrate advantages of the double cell notch filter using BERLinPro SRF gun cavity as an example with its simple design modification

Design considerations for a superconducting linac as an option for the ESS

An approach for a superconducting high-current proton linac for the ESS has been discussed as an option in the "Proposal for a Next Generation Neutron Source for Europe-the European Spallation Source (ESS)". The following work studies the technical and economic conditions for a superconducting linac at the high-energy end of the proposed accelerator system. The use of superconducting elliptical cavities for the acceleration of high-energetic particles beta =v/c-1 is certainly state of the art. This is documented by many activities (TJNAF, TESLA, LEP, LHC, and KEK). A design study for the cavities is described in another paper on this conference. For low energy particles ( beta <<1) quarter wave type cavities and spoke-type cavities have been discussed. The main motivation for this study is the expectation of significant cost reduction in terms of operational and possibly investment cost. (5 refs)