Broadband Oscilloscope Tube

New transmission systems which employ binary pulses and regeneration1 require pulses which are a few millimicroseconds in length. One of the primary characteristics of short pulses is the wide bandwidths required for any system which is to handle them. The advantages of using a wideband system have been discussed by others 2,3 and in this paper we will describe an oscilloscope which is capable of presenting a visual display for these millimicrosecond pulses. In a conventional oscilloscope which uses a pair of plates to deflect the electron beam the frequency range is limited to the extent that a typical tube might have a response which is down by 3 db at 60 mc. This bandwidth is limited by the transit time of the electrons through the deflection system. This time interval should be short as compared to the period of the RF voltage on the plates. We can decrease the time with a resulting increase in bandwidth by shortening the axial length of the plates and increasing the speed of the electrons. Both of these factors, however, tend to decrease the sensitivity which we define as the deflection of the beam measured in units of spot diameters for a unit input voltage. A much improved method of overcoming the transittime problem has been suggested by Pierce4 where he uses a slow traveling RF wave to deflect the beam. The deflecting voltage travels at the same speed as the electrons and consequently a given electron sees 447