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| Home > Publications database > Further improvement of mid-T heat treated SRF cavities for high gradients - recent DESY R&D towards high performance cavities for an EuXFEL upgrade |
| Home > Publications database > Further improvement of mid-T heat treated SRF cavities for high gradients - recent DESY R&D towards high performance cavities for an EuXFEL upgrade |
| Talk (non-conference) (Other) | PUBDB-2024-07761 |
2024
Abstract: The application of heat treatments on 1.3 GHz TESLA type cavities in ultra-high vacuum at 250Β°C to 350Β°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 π0 in dependency of the accelerating electric field strength πΈπππ. First, a significant increase of π0 up to 5 Β· 1010 at 2 K can be observed. Second, the so-called anti-Q-slope occurs. And third, the maximal gradient πΈπππ 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 350Β°C or of 20 hours at 300Β°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 120Β°C to 130Β°C. The subsequent reproducible π0 (πΈπππ)-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 π0 values of more than 3 Β· 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.
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