Retarding Field Energy Analyzer (RFEA)

Project Overview

An RFEA is designed to measure the Ion Velocity Distribution Function (IVDF) of a plasma. This is necessary when conducting plasma research, as was the case with the exploration of EHT's electrodeless plasma source. It functions by having a set of grids at different potentials that repel electrons and allow only ions above a certain energy through the system. Those ions with energies greater than the "discriminator" voltage (which can be varied) make contact with the back plate, resulting in a current through, and thus a voltage across, the shunt resistor. This voltage can be de-convoluted to find the IVDF.

This custom RFEA design is constructed of a tantalum housing, with a thin (1mil) polyimide sheet around the inside. A stack of polyimide insulating sheets separates charged tantalum meshes, spaced to appropriate distances. A CAD model of the RFEA can be seen at right.

Skills Demonstrated / Gained

  • Developing an understanding of plasma diagnostics
  • Tantalum lathing (not easy)
  • Micro-machining, such as drilling through-holes for #000-120 & #00-90 screws
https://lh3.googleusercontent.com/QiW7D3QtQjCs2ULlCrPWkCIg1fSscTF0444ITipOkHlGbblFzy5K2rAdm9sj6o2qIcBGmbEOa9QMoF0B2MpdBwLbnDGARiihbdBQJCaAR0JD9h1LjewT27TQh0Ek0hOvc2w1BJVp9rQCxlO2u49JfPWUxvWPjaaTLLUbOCp6C0du7CfVXWLrnlehXmi3OOVwT8PQXC8XKRR_ece4IKQhOsRX6l9T6z81UIJM7cl3eEY5iWTK9TP36qzsje_UabgTQgNfItMjwP_T1TQpLOlH-h5vL4RTTKoTBTiRS5qk4BTtslksxVTjS_yD7j2DnotZ3aEr_tu7avz1YKJOTFp1OYoLgajXULhp88ExyNgycvGmziHXjHJ07n_USS-NubNpAeABZ_2aP24C7cxVTjImRtMbaHTlqI0Kx3uN_Y7PGfNgc4CX1waOIms9gFRWxR_pt0jxrC1hDJBGYD94NveSSKONCg4sp6EsPLVdhv2pcFfJdI8yJHwHQzaFoDSTJVmeylYHcVFWZbVg6sWuYOvfEYk4FXmbI2XCpv7ple3cYh8xlWkvpNdOFob8WZltvaCAeaCAPx-7qau_EjMVMvPqQ_7NN2cO2prT=w932-h815-no

CAD design of RFEA


https://lh3.googleusercontent.com/3h91Tuaf0bma7n5owVeymwV3waNEjJDIs3ColQKU4PkFrBjehPVJVZWS-0vLEsRDDtuGOI6jfkhK9WuRE-SKWeR9AbTnzXvfCqu2zavTapW1t_5Tj8ghH3b_yw__KkLbkNzNXokZMsvBf6My4Spmh4-ffokT5vwBnSIEIexTKnq14tTuOcQf_qWK3brlp_54FR2q_4cuWgYFfDDHkTKa8FsSolqOIROHUtOf24GUcmeFjFYxojyNrWh7iqP9mYcyL5PDos0979irRLIZ4ja7Wex3wz14xWlUIWxmGYVuIU7MeYalmwZ6k6MB02JMsqE2tuvsXAIlPx4a9xbmeWNWC_nrDqDTd6duioXL1yuC8VhXRl13W8RNQeTN8M9cdzuyUsqu7IXDP5OyxRkYunXFxiL9NoA9E-5liIHLwZ_QQwoGrxWeVhT8eQnzwSqhll-JnvIjzGnj0ZQTN2dMucqu389ZxL0gbv0DzrdGUZStyLhQ_1JmGTwMyVLnvwrFg7k1qnae5PZfq3vDlEh4veQwPhcdY9zVbVgqb7o2I8FBBEhbA4qB2D-6YuAskkS7EGtM-nE-jRgRZM_EhwdjkrGYh_XjpLwiZk5i=w558-h406-no

Grid voltages of RFEA