Related papers: Comment on Field-dependent surface resistance for …
Small (compared to coherence length) weak superconducting defects when located at the surface, combined with the proximity and percolation effects, are claimed responsible for various observations with superconducting rf accelerating…
Identifying the loss mechanisms of niobium cavities enables an accurate determination of applications for future accelerator projects and points to research topics required to mitigate current limitations. For several cavities an increasing…
Many modern and proposed future particle accelerators rely on superconducting radio frequency cavities made of bulk niobium as primary particle accelerating structures. Such cavities suffer from the anomalous field dependence of their…
In a recent publication [Appl. Phys. Lett. 104, 092601 (2014)] Ciovati et al. claim that: 1) thermal effects were disregarded in our original work [*]; 2) increase of $Q$ at $T=2$ K up to about $B\sim$100 mT in nitrogen doped cavities is…
Niobium superconducting radiofrequency cavities enable applications in modern accelerators and quantum computers. However, the surface resistance significantly deteriorates the cavities performance. Nitrogen doping surface treatment can…
We report a surface treatment that systematically improves the quality factor of niobium radio frequency cavities beyond the expected limit for niobium. A combination of annealing in a partial pressure of nitrogen or argon gas and…
We report a strong effect of the cooling dynamics through $T_\mathrm{c}$ on the amount of trapped external magnetic flux in superconducting niobium cavities. The effect is similar for fine grain and single crystal niobium and all surface…
Comment on Proximity breakdown of hydrides in superconducting niobium cavities [arXiv:1212.3384].
Experimental data on N-doped superconducting (sc) cavities are further analyzed which contribute to confirm a recently proposed model explaining the increase of the Q-value versus the accelerating gradient.
The surface resistance Rs of superconducting cavities prepared by sputter coating a thin niobium film on a copper substrate increases significantly stronger with the applied RF field compared to cavities of bulk material. A possible cause…
The dependence of the Q-value on the RF field (Q-slope) is actively studied in various accelerator laboratories. Although remedies against this dependence have been found, the physical cause still remains obscure. A rather straightforward…
Superconducting niobium film cavities deposited on copper substrates (Nb/Cu) have suffered from strong field-dependent surface resistance, often referred to as the Q-slope problem, since their invention. We argue that the Q-slope may not be…
Previous work has demonstrated that the radio frequency surface resistance of niobium resonators is dramatically reduced when nitrogen impurities are dissolved as interstitial in the material. The origin of this effect is attributed to the…
The Q-factor of superconducting accelerating cavities can be substantially improved by a special heat treatment under N2 atmosphere (N-doping). Recent experiments at Fermi National Laboratory investigated the dependence of Q on the RF…
In a recent comment [arXiv:1405.2978v1 (2014)] Romanenko and Grassellino made unsubstantiated statements about our work [Appl. Phys. Lett. 104, 092601 (2014)] and ascribed to us wrong points which we had not made. Here we show that the…
Recent advancement in superconducting radio frequency cavity processing techniques, with diffusion of impurities within the RF penetration depth, resulted in high quality factor with increase in quality factor with increasing accelerating…
We present a general method to derive the magnetic field dependence of the surface resistance of superconductors from the Q-curves obtained during the cryogenic tests of cavities. The results are applied to coaxial half-wave cavities,…
This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance,…
There is a need to better understand the intrinsic limit of radiofrequency (RF) surface impedance that determines the performance of superconducting RF cavities in particle accelerators. Here we present a field-dependent derivation of…
The radio-frequency surface resistance of niobium resonators is incredibly reduced when nitrogen impurities are dissolved as interstitial in the material, conferring ultra-high Q-factors at medium values of accelerating field. This effect…