Vélez, A.; Frahm, A.; Knobloch, J.; Neumann, A.: Cold Bead-Pull Test Stand for SRF Cavities. In: Proceedings of LINAC 2016LINAC, 2016. - ISBN 978-3-95450-169-4, p. THOP03/1-3
http://linac2016.vrws.de/papers/thop03.pdf
Open Access Version
Abstract:
Bead-pull measurements represent a final step in the fabrication process of an SRF cavity. These tests allow to characterise the flatness of the field profile in order to mechanically tune the cavity to achieve design specifications. The realization of a bead-pull measurement is always performed at room temperature and therefore it is influenced by the material physical properties resulting into higher surface losses as compared to the superconducting state. Moreover, questions like mechanical deformation due to asymmetrical thermal shrinkage through the cool-down process and the stress created by the tuner actuation have not yet been answered experimentally. In this paper, an upgrade of the former Cold-Bead pull system developed by HZB [1] is presented. This test-stand is capable of holding a 9-cell Tesla cavity at LHe temperature providing a realistic insight to cavity parameters under operation conditions. In addition, a copper test pill-box is placed in series with the multi-cell cavity in order to perform 1.8K calibration of the bead. Test results of the commissioned test-stand prototype are presented on this paper.