Nonlinear power handling of YBa2Cu3O7-x films and microwave devices

Physical mechanisms which limit the power handling of YBa2Cu3O7-x films and devices are discussed in terms of a quantitative classification scheme. Th e possible limitations are devided into magnetic or thermal, and global or local in nature. Analytical estimations are compared with measurements of Y Ba2Cu3O7-x films (O = 1 "-2 ") using a niobium-shielded sapphire resonator at 19 GHz, and disk resonators at 2 GHz. Magnetic effects are found to play an essential role in nonoptimized films in terms of weak-links, and in hig h-quality films if the lower critical field B-cl is reached. The majority o f films and disk resonators appear to suffer from microwave heating. Global heating appears predominantly at CW operation. Local heating results mainl y from defects in films of medium quality. Defect-induced quenches are obse rved at moderate field levels, sometimes resulting in an irreversible degra dation of the power handling.