Tests on MgB2 for application to SRF cavities

Magnesium diboride (MgB2) has a transition temperature (Tc) of ~40 K, i.e., about 4 times higher than niobium (Nb). Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb at 4 K and seems to have much less power dependence than high-Tc materials such as YBCO. However, it was also found that it will depend on the way you deposit the film. The result from on-axis pulsed laser deposition (PLD) showed rapid increase in Rs with higher surface magnetic fields compared to the film deposited with reactive evaporation method.