M-16

Eight-segment interdigital (squirrel cage) magnetron designed by Henri Gutton at CSF in 1938. It was the first magnetron with oxide-coated filamentary cathode. Early prototypes were specified for operation from 30 down to 6 cm wavelength, giving about 5 watts with an efficiency close to 15%.

Gutton was in touch with E.C.S. Megaw, who suggested a spiral-wound cathode, to increase the emitting surface. Early in 1939 new prototypes gave about 50 W. Few months later a new prototype was showed to Megaw in his last visit to CSF in June 1939. In the new prototype the cathode was an oxide-coated nickel cylinder heated from inside by the tungsten filament. Peak power of 300 W was measured furing the visit of Megaw. Late in 1939 a new improved design was capable of giving 1 kW peak power at 16 cm.

Two samples of this magnetron were brought by Maurice Ponte to Megaw in April 1940, just before German troops entered in Paris. Megaw was designing its six-cavity E1189 magnetron when he could handle Gutton's samples. Readily he adapted his design to build the first E1189 prototype with a spiral-wound oxide-coated filamentary cathode and the second one recalculated  to embody the oxide-coated indireclly-heated cathode.