Abstract: An electron gun arrangement includes a cathode having a front surface and control grid located in front of it. The control grid is mounted via a cylindrical support on a Kovar mount. The cathode is supported by a cylindrical support mounted on a Kovar support. Ceramic material being located between the two supports. The vacuum envelope within which the electron gun is contained includes the Kovar support and a flexible member with which it makes a vacuum seal, this member being of copper. The copper member is sealed to a ceramic cylinder via metal flanges. The assembly permits the spacing between the cathode and grid to be maintained while the copper member permits thermal expansion to occur to maintain vacuum integrity.

Abstract: A grid for use in a linear electron beam tube such as an IOT or TWT includes a grid section and a focus electrode between which is included an accommodation portion. The grid is mounted in the tube by a mounting flange around its outer periphery. During use, the grid section becomes hot and consequently expands but the mounting flange remains relatively cool being connected to a relatively massive structure. Thin flexible strips of the accommodation section permit movement between the mounting flange and the grid section due to differential thermal expansion, thus minimising distortion to the grid section which might otherwise occur if it were connected directly to the mounting flange and hence fixed in its outer diameter length. In other embodiments, the focus electrode is omitted.

Abstract: An actuator for rotation of coupling means such as a loop in a high frequency resonant cavity includes a rotatable member to which the loop is fixed and a rod located adjacent it. The member and rod have interengaging teeth such that when the rod is moved inwardly or outwardly by an operator it causes the member, and hence the loop, to rotate. This is a compact assembly having components which are simple and easy to facilitate. In a preferred embodiment, the rod is located in a groove in the cavity wall.