An electron gun includes a grid electrode having a thin plate portion in which an electron beam aperture is formed, wherein the thin plate portion is formed by using a die and punch die to bulge a portion of a metal plate in the plate thickness direction to such an extent as to correspond to the desired dimension of the thin plate portion to form a bulged portion and cutting the bulged portion. The scaffold includes one or more trace elements from the group consisting of Cu, F, Fe, Mn, Mo, Ni, Sr, and Zn which are released into the host to support vessel growth. The groups of gaming machines may be defined according to one or more gaming machine characteristics. Further stages may be included to grow one or more further nanowhiskers extending from the nanowhisker of the preceding stage. A dual frame to the element frame is determined and antenna element weights are computed based on the dual frame and the specified system radiation pattern function. The excitation electrode on the upper face side and the fixed electrode are connected to an oscillation circuit.