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Holy, F.; Maier, A. R.; Zeitler, B.; Weingartner, R.; Raith, S.; Kajumba, N.; El Ghazaly, M.; Lauth, W.; Krambrich, D.; Gaupp, A.; Scheer, M.; Bahrdt, J. und Grüner, F. (2014): First spectral measurements of a cryogenic high-field short-period undulator. In: Physical Review Special Topics-Accelerators and Beams, Bd. 17, Nr. 5, 050704 [PDF, 981kB]

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Abstract

Further development of synchrotron light sources and new concepts for free electron lasers require undulators with short periods and high magnetic fields. A promising approach is the cryogenic permanent magnet undulator concept based on an advanced magnet material. This new rare earth alloy (Pr, N)(2) Fe-14 B, shows an increasing remanent field of up to 1.7 T without the limits of spin reorientation transition. This work presents first spectral measurements of a prototype cryogenic permanent magnet undulator, consisting of 20 periods of 9 mm in length, cooled by a closed cycle cryo-cooler to temperatures below 30 K. The K parameter of 0.837 at RT is increased by more than 15% to 0.966, and an increase of the third harmonics photon flux of up to 66% was achieved. A possible degradation of the on-axis field quality due to thermally induced magnetic field errors, deduced from the measured bandwidth of the spectrum, is below the limits of the detector resolution of 2%.

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