  We investigate the effect of high temperature treatments followed by only
high-pressure water rinse (HPR) of superconducting radio frequency (SRF)
niobium cavities. The objective is to provide a cost effective alternative to
the typical cavity processing sequence, by eliminating the material removal
step post furnace treatment while preserving or improving the RF performance.
The studies have been conducted in the temperature range 800-1000C for
different conditions of the starting substrate: large grain and fine grain,
electro-polished (EP) and centrifugal barrel polished (CBP) to mirror finish.
An interesting effect of the grain size on the performances is found. Cavity
results and samples characterization show that furnace contaminants cause poor
cavity performance, and a practical solution is found to prevent surface
contamination. Extraordinary values of residual resistances ~ 1 nOhm and below
are then consistently achieved for the contamination-free cavities. These
results lead to a more cost-effective processing and improved RF performance,
and, in conjunction with CBP, open a potential pathway to acid-free processing.
