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AKBP: Arbeitskreis Beschleunigerphysik

AKBP 6: SC Resonators

AKBP 6.8: Vortrag

Dienstag, 10. März 2015, 15:30–15:45, BZ.08.06 (HS 1)

Studying Superconducting Samples with a Quadrupole Resonator — •Raphael Kleindienst, Jens Knobloch, Oliver Kugeler, Andrew Burrill, and Sebastian Keckert — Helmholtz-Zentrum-Berlin

Modern CW accelerators increasingly rely on superconducting cavities, which currently obtain quality factors well above 10¹⁰, corresponding to surface resistances below 10 nΩ. To reach such high quality factors, all processes that can affect the material properties of either bulk niobium or thin superconducting films need to be thoroughly understood. Measuring the superconducting properties of flat samples in comparison to entire cavities is useful, as they are fabricated more easily, and the influence of geometric and mechanical effects is reduced.

Presently, only few facilities exist capable of measuring the surface resistance of superconducting samples with a resolution in the nano-ohm range over a wide temperature span. A dedicated test stand consisting of a Quadrupole Resonator (QPR) has therefore been constructed at the Helmholtz Zentrum Berlin (HZB).

Taking as a baseline the 400MHz QPR at CERN, the design was adapted and optimized to 433 MHz, making available the higher harmonic mode at 1,3GHz. After production by Niowave, the resonator was brought to Jefferson Lab for surface processing and a first RF test. The first cooldown with the complete assembly was performed in the new vertical test stand at HZB. The results for a large grain niobium sample are presented.