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TY - CONF AU - Palczewski, A.D. AU - Kelley, M.J. AU - Reece, C.E. AU - Tuggle, J. ED - Yamazaki, Yoshishige ED - Facco, Alberto ED - McCausey, Amy ED - Schaa, Volker RW TI - Investigation of Nitrogen Absorption Rate and Nitride Growth on SRF Cavity Grade RRR Niobium as a Function of Furnace Temperature J2 - Proc. of LINAC2016, East Lansing, MI, USA, 25-30 September 2016 C1 - East Lansing, MI, USA T2 - Linear Accelerator Conference T3 - 28 LA - english AB - The current state of the art processing of niobium superconducting radio frequency cavities with nitrogen diffusion is performed at 800C in a furnace with a partial pressure of approximately ~20 mtorr of nitrogen. Multiple studies have shown the bulk of the nitrogen absorbed by the niobium forms a thick (1-3 microns) non-superconducting nitride layer which must be removed to produce optimal RF results. The depth profiling of interstitial nitrogen and surface nitrides has already been probed using SIMS measurements. These measurements have also been modeled by extrapolating data from nitride growth studies performed at atmospheric pressure and temperatures above 1000 C (**). One open question is whether there is a diffusion zone at lower temperature in which the niobium will absorb nitrogen but not create a non-superconducting nitride layer; or is the absorption of nitrogen only possible by first forming a nitride buffer layer which then frees up nitrogen for absorption. A systematic study of absorption rate vs. temperature and correlated SIMS measurements needs to be performed to answer this question. We report on the absorption rate vs. temperature from 400 C to 900 C of cavity grade niobium with metallurgically flat witness samples. The witness samples surface depth profile of NbN via SIMS's will be presented and correlated to the absorption.** PB - JACoW CP - Geneva, Switzerland SP - 744 EP - 747 KW - niobium KW - SRF KW - cavity KW - ion KW - injection DA - 2017/05 PY - 2017 SN - 978-3-95450-169-4 DO - 10.18429/JACoW-LINAC2016-THOP02 UR - http://jacow.org/linac2016/papers/thop02.pdf ER -