||It is well known that low temperature
(100-150)C heat treatment (bake) has positive effects on the
performance of high field EP cavities. More than 40 test results are
analyzed based on single-cell cavity experiments of the
CERN-Saclay-DESY collaboration and nine-cell cavities at DESY. The
average gradient Eacc,max increased from 31.9 MV/m to 35.4 MV/m
after baking. No dependency of Eacc,max and the gain of Eacc,max on the
baking temperature is observed. The Q-value at maximum gradient
Q0(Eacc,max) depends significantly on the bake temperature. The average
Q0(Eacc,max)s are 5.3E9, 9.2E9 and 7.7E9 at bake temperate (100-110)C,
(120-130)C and (130-140)C, respectively. Comparison of BCP and EP
cavities shows that at least 60-80 um EP on a BCP surface is necessary.
More than 10-15 um removal of the surface by BCP will reduce the
performance of an EP cavity.