Design, performance, and theory of long thermionic diodes

We report experimental and theoretical investigations of the properties of thermionic diodes of novel design. The construction of long diodes (up to 30 cm) with indirectly heated cathodes, electrostatically shielded interaction volume, and large solid angle for ion collection is presented in detail. These diodes were designed with a high degree of symmetry in order to minimize both electric and magnetic fields in the interaction region. They are especially suited for ultraweak laser‐induced transitions. We also present the first quantitative theory of the diode’s current versus voltage characteristic; it is shown to agree very well with the experimental results. From the calculated potential distributions and the measured ion trapping times we are able to estimate the diode gain. The (chopping) frequency dependence of the diode gain is described quite accurately by a simple schematizing model. We used two distinct methods to determine the diode gain experimentally and find an agreement with our estimate w...