"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 electrostatic 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 Channing.
"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 suppose 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 the time of transit of all the rounds from new barrel to worn gun gives a figure expressed 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?"