3.6M north10.pdf - Dean-O's Toy Box

182 High-Power Microwave-Tube Transmitters
280
260
I
1
Plate current
-0 - Grid current
7
240
I
I / 1
6
220
200
1600
5
160
160
140
120
100
80
2
60
40
1
20
0
m I 1 I 1 1 1
4
0 12 34 5 6 7 6 9 10
Armte voltage(W)
0
Figure 10-26. Voltage/current relationships of ML-8618 tnode.
The tube was not electrically small, either. It had filament power of over 14
kW (7.5 V at 1880 A), which is about 12 W/A of pulse-cathode emission, and an
anode-average-power-dissipation rating of 500 kW. Another indication of the
reduced grid heating is the maximum pulse duration rating of 0.1 second, or
100,000 p.s. (Remember that grid heating, not cathode emission, is the pulseduration
limiting factor in a thoriated-tungsten filament switch tube.)
This tube is spoken of in the past tense because the application for which it
was primarily intended-a giant, experimental pulse modulator—was by no means
an unqualified success, and the tube type itself suffered by association. The magnetically
beamed concept, however, did not die with it.
10.4.6 The ML- 8618 magrzetically beamed triode
This tube, as shown in Fig. 10-25, is a very close relative of the type 8549. The
electromagnetic strategy is the same, but the geometry is planar instead of coaxially
cylindrical. The effect on performance is quite similar, as shown in the voltage/
current relationships of Fig. 10-26. The tube has been rated at as much as 50 kV
anode-voltage hold-off-although it rarely operated above 40 kV. Using the 50-