TY  - CONF
AU  - Steder, Lea
TI  - Further improvement of mid-T heat treated SRF cavities for high gradients - recent DESY R</td><td width="150">
TI  - amp;D towards high performance cavities for an EuXFEL upgrade 
PB  - DESY
M1  - PUBDB-2024-07761
PY  - 2024
AB  - The application of heat treatments on 1.3 GHz TESLA type cavities in ultra-high vacuum at 250°C to 350°C is called medium temperature or mid-T heat treatment. In various laboratories such treatments on superconducting radiofrequency (SRF) cavities result reproducible in three main characteristic features for the quality factor 𝑄0 in dependency of the accelerating electric field strength 𝐸𝑎𝑐𝑐. First, a significant increase of 𝑄0 up to 5 · 1010 at 2 K can be observed. Second, the so-called anti-Q-slope occurs. And third, the maximal gradient 𝐸𝑎𝑐𝑐 of mid-T treated cavities is reduced compared to baseline treatments. At DESY the appearance of a high-field-Q-slope (HFQS) was observed after mid-T heat treatments of 3 hours at 350°C or of 20 hours at 300°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, results of 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°C to 130°C. The subsequent reproducible 𝑄0 (𝐸𝑎𝑐𝑐)-performances results indicate that the low-T bake procedure cures the HFQS like for cavities treated with the EuXFEL recipe. In this talk, cavity performances will be presented with 𝑄0 values of more than 3 · 10^10 at 16 MV/m and accelerating gradients of 32 to 40 MV/m, achieved by the combination of mid-T and low-T treatments.
T2  - Tesla Technology Collaboration Meeting
CY  - 11 Nov 2024 - 15 Nov 2024, Lund (Sweden)
Y2  - 11 Nov 2024 - 15 Nov 2024
M2  - Lund, Sweden
LB  - PUB:(DE-HGF)31
UR  - https://bib-pubdb1.desy.de/record/619620
ER  -