Microwave properties of tuneable TE01 delta mode sapphire-loaded cavity resonators with YBa2Cu3O7-delta endplates

A sapphire loaded cavity resonator with YBa2Cu3O7-delta (YBCO) endplates an d the TE01 delta mode resonant frequency (f(0)) of about 19 GHz at 77 K was prepared and its microwave properties were investigated at low temperature s. Unloaded Q (Q(0)) of the TE01 delta mode resonator appeared to be more t han 1000 000, 600 000 and about 300 000 at 30 K, 60 K and 77 K, respectivel y, at f(0) similar to 19.56 GHz with the sapphire rod sandwiched between tw o YBCO endplates. Q(0) appeared to decrease as the gap distance (s) between the sapphire rod and the top endplate increased for the resonator with YBC O endplates at 30 K, which was in contrast with the increase of Q(0) for in creasing s for the cavity resonator with copper endplates. Microwave losses from the surrounding copper walls appeared to reduce Q(0) of the TE01 delt a mode resonator with YBCO endplates significantly at low temperatures. Exp erimental values of the TE01 delta mode resonant frequencies appeared to ag ree well with both the calculated values from analytic expressions and the simulated values from a commercial software within 1.3%. Variations in f(0) upon the gap distance were more than 4.8% between s = 0 mm and 1 mm, with Q(0) of the TE01 delta mode resonator about 770 000, 530 000 and 350 000 at s = 1 mm at 30 K, 60 K and 77 K, respectively.