Astounding Science Fiction (British Edition), April 1944 — page 14: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

12 accelerate the electrons emitted from the cathode, they are subjected to the attraction of an anode which is operating at a high positive potential. The electrons leave the cathode, and as they are attracted by the positive anode, they begin to move. “Now it is common to speak of the velocity of an electron by stating the quan- tity of volts that the electron has fallen through. The higher the voltage difference between cathode and anode, the faster the electron will go. “But the stream of electrons will be diverged if it falls through a field of increas- ing positive potential. In order to bring the stream to a focus, we must follow the first anode with another anode of a potential less than the first anode but still higher than the cathode. That bollixes up the works. It focuses the stream and slows it at the same time. So we follow this anode with another high positive electrode and speed them up again, and then focus them and so on until we get the required velocity. These anodes are shaped like rings so that their electro- static effect will exist in the center of them; the beam passes through this center.” “In other words the ring-shaped electrodes are electrostatic lenses?” ‘Nope. It is the space between them. The lens is either convex or concave depending upon whether the voltage gradient is from positive to less positive or if it is positive to more positive, respectively. In an electro- static lens for electrons, the thing is not like a glass lens for light. Whether your lens is diverging or converging depends upon which way your electron stream is running through it. With light, a convex lens will converge the light no matter which direction the light is coming from.” “Uh-huh. I see in a sort of vague manner. Now, fellows, go on from there. What’s necessary to make this dingbat tick?” “I want to think out loud,” said Chan- ning. “That’s nothing unusual,” said Arden. “Can’t we get into Joe’s? You can’t think without a tablecloth, either.” “What I’m thinking is this, Walt. You’ve been trying to squirt electrons like a fireman runs a hose. Walt, how long do you sup- pose a sixteen-inch rifle would last if the explosives were constantly replaced and the fire burned constantly?” “Not long,” admitted Walt. “A gun is an overloaded machine,” said Don. “Even a little one. The life of a gun barrel is measured in seconds; totaling up ASTOUNDING SCIENCE-FICTION the time of transit of all the rounds from new barrel to worn gun gives a figure ex- pressed in. seconds. Your electron gun, Walt, whether it be fish, flesh, or fowl, must be overloaded for an instant.” “Is overload a necessary requirement?” asked Arden. “It seems to me that you might be able to bore a sixteen-inch gun for a twenty-two. What now, little man?” “By the time we get something big enough to do more than knock paint off, we'll have something bigger than a _ twenty-two,” grinned Channing. “I was speaking in terms of available strength versus required punch. In the way that a girder will hold tre- mendous overloads for brief instants, a gun is extremely overloaded for milliseconds. We'll have a problem—”’ “O.K., aside from that, have you figured out why I haven’t been able to do more than warm anything larger than a house brick?” “Sure,” laughed Channing. “What hap- pens in a multigrid radio tube when the suppressor grid is hanging free?” “Charges up and blocks the electron stream ... hey! That’s it!” “What?” asked Arden. “Sure,” said Walt. “We fire off a batch of electrons, and the first contingent that ar- rives charges the affair so that the rest of the beam sort of wriggles out of line.” “Your meteor is going to take on a charge of phenomenal negative value, and the rest of your beam is going to be deflected away, just as your electron lenses deflect the original beam,” said Channing. “And now another thing, old turnip. You're squirting out a lot of electrons. That’s much amper- age. Your voltage—velocity—is nothing to rave about. Watts is what you want, to corn a phrase.” “Phew,” said Walt. “Corn, he says. Go on, prodigy, and make with the explana- tions. I agree, we should have more voltage and less quantity. But we're running the stuff at plenty of voltage now. Nothing short of a Van Der Graf generator would work— and while we’ve got one up on the forty- ninth level, we couldn’t run a supply line down here without reaming a fifty-foot hole through the Station, and then I don’t know how we'd get that kind of voltage down here without .. . that kind of stuff staggers the imagination. You can’t juggle a hundred million volts on a wire. She’d squirt off in all directions.” “Another thing, whilst I hold it in my mind,” said Channing thoughtfully. “You comiclooks ©