The Double Quarter Wave (DQW) Crab Cavity was designed to rotate the colliding bunches and in consequence to increase the luminosity of the LHC machine. Prior to launching series production detailed RF validation tests, both without and with beam, were performed at CERN. For the cavity preparation and RF performance validation before installation in the cryomodule, a comprehensive programme of RF surface preparation and cavity performance evaluation in liquid helium temperatures were carried out. Due to the unusual geometry of the DQW cavity there were a number of challenges both in preparation and RF testing that had to be addressed. The results and conclusions of the preparation process and cavity performance in the vertical test cryostat are presented in this paper in the form of a short technical report.
The High Luminosity LHC (HL-LHC) Project is an upgrade program of the Large Hadron Collider (LHC) at CERN, focused on increasing the luminosity, thus significantly enhancing the potential to discover new physics from rare events. Among many activities ongoing in this framework, the implementation of novel superconducting radio frequency (SRF) cavities - especially Crab Cavities - is foreseen for compensation of the bunch crossing angle, which is a reducing factor for LHC luminosity. Two different crab cavity designs have been developed: the Double Quarter Wave (DQW) and the Radio Frequency Dipole (RFD). A prototype cryomodule, hosting two DQW cavities, has been fabricated and assembled3 for validation tests, which are currently ongoing in the Super Proton Synchrotron (SPS) at CERN. Since 2016 the engineering team from IFJ PAN has been contributing to the Crab Cavities & RF project (Work Package 4 of the HL-LHC Project). This contribution has included the following activities: mechanical, electrical and vacuum preparation of DQW crab cavities for cold tests in the vertical cryostat, as well as the assembly process of the fully-dressed DQW cavities. After successful RF cavities qualification, the assembly of the DQW cryomodule and its preparation for the tests was also performed with the participation of the IFJ PAN team.
New superconducting transfer lines known as Superconducting Links (SC Links) are being developed at CERN for the remote powering of upgraded superconducting insertion magnets in the framework of the High Luminosity Large Hadron Collider (HL-LHC) project. The purpose of the SC Links is to transfer current from power converters located in radiation-free areas to magnets located in the vicinity of the LHC interaction points via shorter REBCO High Temperature Superconductor (HTS) current leads. HTS current leads, connecting the superconducting link to the conventional cables of the power converters, allow a very high current densities to be carried and significantly reducing the cooling power required for conventional cables. The expected length of the superconducting lines can reach 130 m, depending on the location, spanning a vertical distance of about 80 m. Each of the link containing an assembly of MgB<sub>2</sub> cables supplying different systems, which will transfer a total current exceeding 150 kA. In order to validate the selected technical solutions and materials as well as to confirm the design reliability and robustness of the SC Links, the construction of a fully functional 60 m long demonstrator (DEMO1) of the 18 kA circuit of the SC Link is ongoing. Since 2018, the engineering team from IFJ PAN has been contributing to the Cold Powering activity (Work Package 6a of the HL-LHC project). This contribution includes among others, preparing of assembly procedures for the system, producing components for the demonstrator, assembling the demonstrator and participating in tests.
The European X-ray Free Electron Laser (XFEL) is currently under construction in Germany in Hamburg area. Part of
the XFEL is a 2.1 km long superconducting linear accelerator which consists of 100 accelerating cryomodules. Each
accelerating cryomodule consist eight superconducting 9-cell Niobium cavities, one superconducting magnet and
current leads unit. The mentioned components (current leads, cold magnets and current leads) are tested in dedicated
test facilities before installing in the cryomodules. After completing each cryomodule is tested in dedicated test facility
before installation in the XFEL tunnel. The testing procedures for tests of the cold magnets, current leads, cavities and
cryomodules were prepared with use of DESY expertise from TTF (Tesla Test Facility) Collaboration and FLASH
(Freie-Elektronen-Laser in Hamburg). This paper describes the whole testing procedure covering incoming and outgoing
inspections. An update of testing procedures including the full automation of testing process and the preliminary tests
results are presented as well.