Jan-Hendrik Thie

Since 15 years a prototype semi automatic cavity tuning machine is used at DESY to tune field flatness and concentricity of TESLA [1] shape nine cell cavities for FLASH [2]. Based on this experience a further development work was done in a collaboration effort among FNAL, KEK and DESY to support the high throughput of series cavity productions necessary for new projects like the European XFEL [3], the ILC project, Project “X ” and other SRF based future projects. Initially four machines were built within the collaboration at DESY. Two of them will be delivered and operated by the cavity vendors for tuning the XFEL cavities. The remaining two machines are delivered to FNAL for commissioning. One of them will be passed on to KEK. In the following the mechanical design and functionality of these machines is described. Special attention refers to safety aspects for the machines operation at industry and the fulfillment of requirements according to the EC directive of machinery.

The European x-ray free electron laser is under construction at Deutsches Elektronen-Synchrotron (DESY). The electron beam energy of up to 17.5 GeV will be achieved by using superconducting accelerator technology. Final prototyping, industrialization, and new infrastructure are the actual challenges with respect to the accelerating cavities. This paper describes the preparation strategy optimized for the cavity preparation procedure in industry. For the industrial fabrication and preparation, several new hardware components have been already developed at DESY. The design and construction of a semiautomated rf-measurement machine for dumbbells and end groups are described. In a collaboration among FNAL, KEK, and DESY, an automatic cavity tuning machine has been designed and four machines are under construction. The functionality of these machines with special attention to safety aspects is described in this paper. A new high pressure rinsing system has been developed and is operational.

For more than 20 years DESY has gained experience in tuning cavities of TESLA [1] shape nine cell cavities for FLASH [2] to field flatness and concentricity. Based on this experience four automatic cavity tuning machines were developed and built by a collaborative effort among FNAL, KEK and DESY [3] to support the high throughput of series cavity productions necessary for new projects like the European XFEL [4], the ILC project, Project “X” and further SRF based future projects. In the meantime two machines were delivered to the collaborative partners KEK and FNAL. The remaining two machines at DESY, are regularly used since several months. A large number of cavities of different types and at different production stages have been automatically tuned for FLASH and also in preparation for the European XFEL series cavity production starting this summer.

A future upgrade of the European XFEL (E-XFEL) foresees an additional CW operation mode, which will increase the flexibility in the photon beam time structure [1–3]. One of the challenges of this operational mode is the need fora CW operating photo injector. We believe that using an SRF gun is the preferred approach as the beam parameters of normal conducting pulsed guns can be potentially met by SRF guns operating CW. For more than a decade DESY, incollaboration with TJNAF, NCBJ, BNL, HZB and HZDR, has performed R&D to develop an all superconducting RFgun with a lead cathode. In the frame of E-XFEL CW upgrade feasibility studies, the SRF-gun R&D program gained more attention and support. Within the next few years we would like to demonstrate the performance of the all superconducting injector required for the E-XFEL upgrade. The selected approach offers advantages w.r.t. the cleanliness of the superconducting surface, but requires a complete disassembly of a cryostat and stripping the gun cavity in a cleanroom to exchange the cathode. Thus it is practical only when the life time of the cathode is at least several months. In this paper we present the actual status of the R&D program, next steps and the longer term plans.

Serial production of superconducting cavities for European-XFEL will be completed at E.ZANON by the end of 2015. For that reason we can summarize the results and present the statistics of industrial cavity fabrication. Many parameters have been traced during different steps of cavity production. The most interesting of them, as cavity length, frequency, field flatness and eccentricity, are presented and discussed.