A selection of point of view camcorders : Technical specifications, classroom trials, and potential applications

About 50 nine-cell cavities of the recent fine-grain niobium cavity productions have been analysed with respect to maximum and usable gradient in the first and last vertical RF acceptance test, respectively. Parameters of the analysis were the manufacturer of the cavities, the location of the Main EP (=> industry or in-house), the final surface treatment (=> final 40 μm EP or short 10 μm “Flash BCP) and the cavity preparation strategy (=> vertical acceptance test with or without He-tank welded). Moreover, the effect of a re-processing of field emission loaded cavities by an additional ultra pure high pressure water rinsing (HPR) has been investigated

Superconducting undulator activities at the European X-ray Free-Electron Laser Facility

For more than 5 years, superconducting undulators (SCUs) have been successfully delivering X-rays in storage rings. The European X-Ray Free-Electron Laser Facility (XFEL) plans to demonstrate the operation of SCUs in X-ray free-electron lasers (FELs). For the same geometry, SCUs can reach a higher peak field on the axis with respect to all other available technologies, offering a larger photon energy tunability range. The application of short-period SCUs in a high electron beam energy FEL > 11 GeV will enable lasing at very hard X-rays > 40 keV. The large tunability range of SCUs will allow covering the complete photon energy range of the soft X-ray experiments at the European XFEL without changing electron beam energy, as currently needed with the installed permanent magnet undulators. For a possible continuous-wave (CW) upgrade under discussion at the European XFEL with a lower electron beam energy of approximately 7–8 GeV, SCUs can provide the same photon energy range as available at present with the permanent magnet undulators and electron energies. This paper will describe the potential of SCUs for X-ray FELs. In particular, it will focus on the different activities ongoing at the European XFEL and in collaboration with DESY to allow the implementation of SCUs in the European XFEL in the upcoming years

Cavity R&D for TESLA

The cavity research and development which was essential to achieve the performance goals of a Q$_0$ of 10$^{10}$ at an accelerating gradient of 23,5 MV/m for TESLA-500 will be reviewed. Results from the 1,3 GHz nine-cell superconducting niobium cavities will be shown. For TESLA-800 the specifications are a Q$_0$=5×$10^9$ for the accelerating gradient of 35 MV/m. It will be shown that this is achieved regularly in electropolished one-cell cavities. First promising results on nine-cell cavities are shown. For TESLA-800 it is necessary to increase the fill factor of the linac. This is achieved via the superstructure concept. The first succesful test with a piezoelectric tuner to compensate the frequency detuning during the rf pulse is shown