title: Designs of a microwave TE011 mode cavity for a space borne H-maser.
abstract: Method of Lines and Finite Element Analysis investigations have been performed to optimize parameters in a TE011 mode cavity resonator suitable for a spaceborne hydrogen maser. We report on designs that were explored to find a global maximum in the important design parameters for the microwave cavity used in a hydrogen maser. The criteria sought in this exercise were both the minimization of the total volume of the cavity and the maximization of the product of the z-component of the magnetic energy filling factor and the cavity TE011 mode Q-factor (Q.eta). Different configurations were studied. They were a sapphire tube in a copper cylinder, a sapphire tube in a copper cylinder with Bragg reflectors, and spherical copper cavities both empty and sapphire-lined on the inside cavity surface. At 320 K, the simulations resulted in an optimum product Q.eta = 4.9 x 10(4), with an inner cavity radius of 80 mm and unity aspect ratio. This represents a 54% improvement over an earlier design. The expected increase in the product Q . eta) with the inclusion of Bragg reflectors to the sapphire tube was not achieved. Moreover, the z-component of the magnetic energy filling factor was greatly reduced due to an increase in the radial magnetic field. The sapphire-lined spherical cavity showed no better performance than an equivalent-sized empty copper spherical cavity. For the empty cavity the simulations resulted in the product Q.eta = 4.4 x 10(4). The empty spherical cavity resonator is not suitable for the spaceborne hydrogen maser as the total volume in this case is 33% larger than that of the optimized sapphire tube resonator.
authors.affiliation: FSM Research Group, School of Physics, The University of Western Australia, Crawley, WA, 6009, Australia. john@physics.uwa.edu.au
authors.forename: John G
authors.initials: JG
authors.lastname: Hartnett
authors.forename: Michael E
authors.initials: ME
authors.lastname: Tobar
authors.forename: Paul L
authors.initials: PL
authors.lastname: Stanwix
authors.forename: Takao
authors.initials: T
authors.lastname: Morikawa
authors.forename: Dominique
authors.initials: D
authors.lastname: Cros
authors.forename: Olivier
authors.initials: O
authors.lastname: Piquet