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TY - CONF AU - Wolff-Fabris, F. AU - Decking, W. AU - Hedqvist, A. AU - Hellberg, F. AU - Nölle, D. AU - Pflüger, J. AU - Schmidt-Föhre, F. AU - Sinn, H. ED - Schaa, Volker R.W. ED - Decking, Winfried ED - Sinn, Harald ED - Geloni, Gianluca ED - Schreiber, Siegfried ED - Marx, Michaela TI - Absorbed Radiation Doses on the European XFEL Undulator Systems During Early User Experiments J2 - Proc. of FEL2019, Hamburg, Germany, 26-30 August 2019 CY - Hamburg, Germany T2 - Free Electron Laser Conference T3 - 39 LA - english AB - The EuXFEL is a FEL user facility based on a superconducting accelerator with high duty cycle. Three gap movable SASE Undulator Systems using hybrid NdFeB permanent magnet segments are operated. Radiation damage on undulators can impact the quality of the SASE process and ultimately threaten user operation. We observed [1] in the commissioning phase doses up to 4 kGy and 3% demagnetization effect in a diagnostic undulator. Currently all SASE systems are used for user photon delivery and in this work we present characteristics of the absorbed radiation doses on undulators under stable conditions. Doses on the upstream segments are found to be originated in the event of occasional high energy electron losses. In contrast, towards the downstream end of a SASE system, individual segments show persistent absorbed doses which are proportional to the transmitted charge and are dominated by low energy radiation. This energy-dependence depiction shall result in distinct radiation damage thresholds for individual segments. Portable magnetic flux measurement systems allow in-situ tunnel assessment of undulator properties in order to estimate radiation dose limits for future user operation. PB - JACoW Publishing CP - Geneva, Switzerland SP - 569 EP - 573 KW - undulator KW - operation KW - FEL KW - photon KW - radiation DA - 2019/11 PY - 2019 SN - "" SN - 978-3-95450-210-3 DO - doi:10.18429/JACoW-FEL2019-WED02 UR - http://jacow.org/fel2019/papers/wed02.pdf ER -