| Paper | Title | Page |
|---|
| TUP24 | Studies of the high field anomalous losses in small and large grain niobium cavities | 173 |
| | - A. Romanenko, G. Eremeev, D. Meidlinger, H. Padamsee
CLASSE, Cornell University
| |
| | High field Q-slope in niobium cavities of all grain sizes
remains to be an unexplained phenomenon. Thermometry
studies performed in recent years revealed that distribution
of losses in the high field Q-slope regime is not uniform,
but exhibit a patchy character with some regions being hotter
than other. Results of surface analysis of samples dissected
from "hot" and "cold" regions of small and large
BCP cavities are reported in this contribution. | |
| WE101 | Temperature Map Studies on Nearly Oxide-Free, Thin-Oxide and Standard-Oxide Cavities | 356 |
| | - G. Eremeev, H. Padamsee
CLASSE, Cornell University
| |
| | A few nanometers of niobium oxide cover niobium in
niobium cavities, prepared by standard treatments. Since
the RF penetration depth is a few tens of nanometers, the
niobium oxide and the metal-oxide interface may play role
in RF losses of superconducting niobium. In order to understand
the cause of phenomena such as the high field Qslope,
medium field Q-slope, and residual resistance, it is
important to distinguish the contributions of the niobium
oxide and its interface to losses at medium and high fields.
XPS and Auger studies have shown that it is possible to reduce
significantly the thickness of the oxide layer by heating
to 3000C - 4000C for a few hours in vacuum. Leaving
the surface in the vacuum does not re-grow the oxide layer.
Applying such treatment to a cavity one can reduce the niobium
oxide and measure the superconducting RF properties
of a nearly oxide-free cavity. Then via controllable air exposure
one can re-grow oxide and investigate the change in
properties as a function of exposure. We performed these
experiments and report results of nearly oxide-free, thinoxide
and standard-oxide cavities. | |
 | Slides(PDF) | |