A method of constructing tubes employing planar periodic electrostatic focusing of sheet beams

One of the main reasons why tubes employing planar periodic electrostatic focusing of electron sheet beams have not been used more widely is that extremely precise alignment of tube parts is required in order to achieve good beam transmission. A simple technique for achieving this precise alignment has been developed. This technique, in brief, consists of the assembly of the tube electrodes in two separate halves, the surfaces of which are then ground simultaneously with an abrasive wheel. Finally, the two halves are bolted together at each end. This technique has been employed successfully in the construction of a tube containing a 2.1 in. long electrostatic focusing structure consisting of 19 pairs of plates having a separation of 0.025 in. In this tube, 99.8% of the 0.005 in. thick, 28 µ amp. electron beam was transmitted through the structure with no increase of beam width. This technique can be applied to the construction of any device employing planar periodic electrostatic focusing of a sheet beam. Two possible applications are a transverse-field traveling-wave tube and a parametric amplifier. This technique may also be used for constructing well-aligned electron guns for generating well-collimated sheet beams to be used for other applications, such as slalom focusing and E-type devices.