A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

Eremeev, G. V.

Paper Title Page
WEPMS005 Temperature Mapping Results on the High-Field Q-Slope of 1500 MHz Single Cell Superconducting Radiofrequency Cavities Baked In-situ at 400 C. 2334
  • G. V. Eremeev, H. Padamsee
    CLASSE, Ithaca
  Funding: NSF

The heat treatment of a niobium cavity between 100 C - 120 C for 48 hours substantially improves cavity performance, presumably by healing the nature of the oxide-metal interface, although the nature of the healing is not yet understood. The heat treatment at higher temperatures is found to deteriorate the performance. Our tests on 1500 MHz single cell cavities are always equipped with a temperature mapping system consisting of 700 thermometers. The effect of heat treatment at various temperatures has been studied in detail using the temperature mapping system. In this contribution we report on several interesting findings from studies of a 400 C heat treatment.

WEPMS006 High Gradient Studies for ILC with Single Cell Re-entrant Shape and Elliptical Shape Cavities made of Fine-grain and Large-grain Niobium 2337
  • R. L. Geng, G. V. Eremeev, H. Padamsee, V. D. Shemelin
    CLASSE, Ithaca
  Funding: Work supported by DOE

Based on the encouraging results of the first 1300 MHz 70 mm aperture single cell re-entrant cavities*, we continue the high gradient studies for ILC with new re-entrant cavities made of fine-grain as well as large-grain niobium. These new cavities have smaller aperture of 60 mm, providing a further reduced Hpk/Eacc or a further improved ultimate gradient. Four 1300 MHz 60 mm aperture re-entrant cavities are made, two out of fine grain niobium and the other two out of large-grain niobium. In addition, two elliptical shape 1500 MHz cavities are also made out of large-grain niobium. We present the testing results of these cavities.

* R. L. Geng et al., PAC2005, p.653.

WEPMS011 Comparative Surface Studies on Fine-grain and Single Crystal Niobium Using XPS, AES, EBSD and Profilometry 2349
  • A. Romanenko, G. V. Eremeev
    CLASSE, Ithaca
  • H. Padamsee, J. B. Shu
    Cornell University, Ithaca, New York
  Funding: Supported by NSF

As the surface magnetic field in niobium cavities approaches the theoretical critical field, rf losses begin to grow sensitive to increasingly subtle features of the material and the surface. A striking example is the familiar occurrence of the high-field Q-slope, where rf losses increase exponentially with field above an onset field. A surprising feature of the high-field Q slope is its positive response to mild baking at 120 C. But the Q-slope returns after the first 20 nm of the niobium metal surface is converted to loss-less pentoxide via anodization, a key feature. The latter result suggests that the cause of the fast growing losses resides in the first 20 nm of the rf surface. Although there are several propositions, the exact mechanism for the high-field Q-slope is not yet fully understood and demands further research. We are conducting surface analytic studies with XPS, SIMS, and Auger to shed light on the mechanism of the high-field Q-slope. We are comparing the behavior of fine-grain samples with single crystal samples, BCP treatments with EP treatments and properties before and after 120 C bake. We also study the effect of baking at temperatures up to 400 C.