Preparatory procedure and equipment for the European x-ray free electron laser cavity implementation

Abstract

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.

Field emitter activation on cleaned crystalline niobium surfaces relevant for superconducting rf technology

“…Three HTs up to 122, 400, and 800 C and of different duration were sequentially applied to the Nb samples and alternated with the FESM measurements. The main parameters of the heating cycles are similar to those used during the Nb cavity fabrication process (HT122, HT800) [10] or to former FE studies (HT400, HT800) [14,15] and listed in Table I. A typical temperature profile with linear warm-up ramp, HT at the nominal temperature (AE 1 C) over a given duration and natural cool-down is shown in Fig.…”

“…Two extended surface polishing schemes, i.e. ''Final EP'' and ''BCP Flash'' [10], have been chosen for the XFEL production. The first one includes 110 m EP to remove the surface damage layer and 40 m final EP and the second one 140 m EP and 10 m final buffered chemical polishing (BCP) correspondingly.…”