| Autor: |
Dhakal, P., Ciovati, G., Myneni, G. R., Gray, K. E., Groll, N., Maheshwari, P., McRae, D. M., Pike, R., Proslier, T., Stevie, F., Walsh, R. P., Yang, Q., Zasadzinzki, J. |
| Rok vydání: |
2012 |
| Předmět: |
|
| Druh dokumentu: |
Working Paper |
| DOI: |
10.1103/PhysRevSTAB.16.042001 |
| Popis: |
Large-grain Nb has become a viable alternative to fine-grain Nb for the fabrication of superconducting radio-frequency cavities. In this contribution we report the results from a heat treatment study of a large-grain 1.5 GHz single-cell cavity made of "medium purity" Nb. The baseline surface preparation prior to heat treatment consisted of standard buffered chemical polishing. The heat treatment in the range 800 - 1400 C was done in a newly designed vacuum induction furnace. Q0 values of the order of 2x1010 at 2.0 K and peak surface magnetic field (Bp) of 90 mT were achieved reproducibly. A Q0-value of (5+-1)1010 at 2.0 K and Bp = 90 mT was obtained after heat treatment at 1400 C. This is the highest value ever reported at this temperature, frequency and field. Samples heat treated with the cavity at 1400 C were analyzed by secondary ion mass spectrometry, secondary electron microscopy, energy dispersive X-ray, point contact tunneling and X-ray diffraction and revealed a complex surface composition which includes titanium oxide, increased carbon and nitrogen content but reduced hydrogen concentration compared to a non heat-treated sample. |
| Databáze: |
arXiv |
| Externí odkaz: |
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