Radar System Engineering

326 THE MAGNETRON AND THE PULSER [SEC. 10.2
ments is a maximum. One quarter of a period later the electric field and
charges have disappeared and currents are flowing around the inside of
the cavities, producing a magnetic field along the hole portion of the
cavities. Figure 10.6b depicts the currents and fields at this instant.
f
Coaxialline output
~ Front pole piece
, Permanent magnet
FIG. 10.5.—Magnetronwith axial cathode and insertedpole pieces.
Figure 10.6c shows the charges and electric fields another quarter period
later.
Figure 10.7 is a view of the magnetron opened out in a plane parallel
to the cathode so that the anode faces lie on a plane. The broken lines
show the paths of magnetic flux at the instant shown in Fig. 10.6b.
Figures 10.6 and 10.7 illustrate the so-called “r-mode” in which
magnetrons normally operate; (m refers to the phase difference between
adjacent anode segments). Actually, the number of possible modes of