Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: A few questions, Richard Hull
Date: Oct 22, 7:51 pm
Poster: Carl Willis

On Oct 22, 7:51 pm, Carl Willis wrote:

>Mean free path is how far the atoms travel >without colliding right? Is this the same as >Debye Length? And recombination is just the >ions becoming neutral by picking up electrons, >right?

You're right about the mean free path, with the possible exception that it is just an average. The Debye length, in my understanding, is how far you have to go in a plasma to get from a charged particle to a location where the field from this charge is completely shielded. It depends on charge density and particle energy.

>What are heated dispenser cathodes? I thought >cathodes just gained electrons.

The cathode is where electons enter a device. (Perhaps you are thinking of a battery, where the cathode is the positive electrode which gains electrons and is chemically reduced.) Heated cathodes are a way to make electrons (other than the secondary electron emission that normally support a gas discharge at higher pressures). This means a hot filament or hot alkaline-earth oxides, which emit electrons.