Chaos in crossed-field devices

Summary form only given. It is well known that the magnetic field has a crucial and somewhat mysterious effect on the performance of crossed-field devices. On the one hand it leads to high electronic efficiency of the beam/e-m field interaction process, largely due to the fact it permits a much higher volume density of e-m radiation (magnetrons), on the other hand it seems to be the source of ´excess noise´, an effect which is particularly troublesome in amplifiers (CFAs). In fact many now suspect that the latter effect is a manifestation of chaos. Recently we have been engaged in the investigation of various ways of generating chaos. Having considered plasma filled devices we have turned our attention to the effect of a magnetic field, taking a smooth anode magnetron as a convenient and relatively simple example. In our presentation we propose to consider methods of investigating the existence of chaos using a computer modelling technique based on MAGIC, a flexible and powerful code. So far we have been able to obtain a numerical agreement between analysis and computation of such simple parameters as Hull´s radius, space-charge distribution and total amount of interelectrode cloud both at low (2 kV) and high (500 kV) anode voltages, in the latter case using relativistic kinematics. Currently we are in the process of developing techniques to recognise the existence of chaos in the system as opposed to ordinary noise. The results of our investigations are available at the time of the Conference.