  Main focus of this study is the investigation of thermodynamics phenomena
responsible for the High Field Q Slope (HFQS) in SRF cavities by Internal
Friction (IF) measurement. Mechanical spectroscopy is, indeed, a
well-established technique to study precipitate formations in BCC materials and
several works on the effects of impurities as N and O on the Snoek peak have
been published so far and will be taken as reference to explain the mechanisms
behind the observed dissipation effects. Internal Friction measurements were
performed in Belgium at IMCE on Nb rectangular shape samples with different RRR
values prepared at Fermilab by using Electro Polishing (EP), N-doping and heat
treatments in order to reproduce the same conditions during the standard
treatments applied on bulk Nb SRF cavities. From IF spectra, the H trapping
mechanism by interstitial atoms (N and O and/or vacancies, depending on the
purity level, RRR) can be easily recognized leading to results that perfectly
corroborate previous findings on Q-disease, HFQS and RRR phenomena.

Applied Physics;Materials Science;Superconductivity