  The application of heat treatments on 1.3 GHz TESLA type cavities in
ultra-high vacuum at 250{\deg}C to 350{\deg}C is called medium temperature or
mid-T heat treatment. In various laboratories such treatments on
superconducting radio frequency (SRF) cavities result reproducible in three
main characteristic features for the quality factor $Q_0$ in dependency of the
accelerating electric field strength $E_{acc}$. First, comparing mid-T heat
treatment with a baseline treatment, a significant increase of $Q_0$ up to
$5\cdot10^{10}$ at 2K can be observed. Second, with increasing accelerating
gradient $E_{acc}$ the $Q_0$ increases up to a maximum around 16 to 20 MV/m.
This effect is known as anti-Q-slope. The third observation for a mid-T heat
treatment compared to a baseline treatment is an often reduced maximum gradient
$E_{acc}$.
  The appearance of a high-field-Q-slope (HFQS) was reported after mid-T heat
treatments of 3 hours at 350{\deg}C or of 20 hours at 300{\deg}C at DESY. Using
the heating temperature and the heating time taken from the temperature profile
of the furnace effective oxygen diffusion lengths $l$ were calculated. In the
follow-up study presented here, a set of three single-cell cavities with
diffusion lengths $l$ above 1700 nm, showing HFQS, were treated with an
additional so-called low-T bake of 24-48 hours at 120{\deg}C to 130{\deg}C. The
subsequent reproducible Q(E) -performances results indicate that the low-T bake
procedure cures the HFQS like for cavities treated with the EuXFEL recipe of EP
and following low-T treatments. As presented in the following, Q values of more
than $3\cdot10^{10}$ at 16 MV/m and accelerating gradients of 32 to 40 MV/m are
achieved.
