Loss tangent measurements of dielectric substrates from 15 K to 300 K   with two resonators: investigation into accuracy issues
  The loss tangent of medium, low and very low loss dielectric substrates (including the Rogers RT Duroid 5880 and 6010.2, LaAlO3, (La, Sr)(Al, Ta)O3, MgO and Quartz) was measured at varying temperatures with two TE01{\delta} dielectric resonators to ensure verification of the tests. The accuracy of the measurements has been researched and discussed for split post dielectric resonator (SPDR) in a copper enclosure and a single post dielectric resonator (SuPDR) in a superconducting enclosure in the temperature range from 15K to 300 K. 
Janina E. Mazierska, Mohan V. Jacob, Dimitri O. Ledenyov and Jerzy   Krupka
cond-mat.mtrl-sci cond-mat.supr-con physics.ins-det