Superconducting Radiofrequency Technology for Accelerators

4 High Q via 300 °C Bake (Mid-T-Bake)

4.1 A Surprise Discovery

Another major discovery with major Q benefits has been the Fermilab invention [179] by Posen of a new procedure, called “mid-T baking, or 300 °C baking.” The treatment raises the Q for medium gradients and cw operation. Figure 4.1 shows several benefits, some unexpected. Despite the absence of N exposure, the Q versus E behavior is similar to N-doping, especially the occurrence of the anti-Q-slope. The low-field residual resistance reaches a very low value to yield a record high Q at 1.5 K. The low field Q-slope (LFQS) disappears. Q values at extremely low fields become higher to open the door to new applications in quantum computing (Chapter 13). A further simplification of the ...