Measurements of the Electrostatic and Electromagnetic Fields of Faraday-Shielded Half-Turn Loop-Type ICRF Antennae

Detailed measurements of both the electrostatic and electromagnetic fields are performed for various types of Faraday shields mounted on PLT ion cyclotron range of frequencies (ICRF) antennae. The data show that the shields have little effect on the electromagnetic fields when the antenna is driven such that it is generating a constant total flux for the various cases. A new type of shield (Type II) is investigated that has no effect on the antenna inductance and performs equally as well as the conventional shields (Type I) in shielding out the electrostatic fields. Measurements indicate, for the shields investigated, that each layer of shield strips degrades the Q by approximately a factor of two.