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: What you should see!
Date: Sep 24, 08:44 am
Poster: Richard Hull
On Sep 24, 08:44 am, Richard Hull wrote:
>The way I understand it is that there are currents that circulate within the grids, first falling into the center then being driven out again. Its this circulation that at higher energy levels returns the ions to points of eventual collisions. Somewhat like convection currents in the atmosphere. If my understanding is correct then what you are saying is Joshua is seeing an inbound current interacting with an outbound current producing the "jet". If I were to carry this mental image out further, I would presume that the ion guns in the advanced fusor don't shoot through the screens for this very reason(among others). My mental images have been known to be wrong from time to time. This would seem to mean to me that the inner grid shape could be optimized to promote these currents. I've just been practicing so far, but the inner grid is a little difficult to make anyway. I'm too picky about the way it looks.
I have left the upper portion intact for the most part as it should be read by all again.
The simple two grid fusor will mime ion gun action to a degree (always lesser), but can be "sweet spotted" to maximize fusion by careful control and balance over the deuterium gas pressure versus voltage at the machine. The beuty is that we can play with air to learn the secrets of this process without wasting deuterium in the beginning.
Joshua's system had too much gas in it (not a high enough vacuum). Thus, his recirculation was near zero and this results in a very short mean free path for ions. This also implies that no ion can reach fusion energy due to the short recirculation path. Remember, the energy of the ion, or electron for that matter, is a function of the potential it falls through while being accelerated. If it crashes into other stuff while being accelerated, it can recombine (deionize), be slowed down by elastic collisions, ionize other atoms in mid stream thus losing enrgy and then imparting part of its energy to a slow neutral, create a metastable atom of slow speed or upon itself deionizing result in just two fast neutrals. The list of possibilities is endless!!!
This is the crux of the matter!
Most vacuum/gas situatiions in experimental physics are controlled rigidly to favor one regime over the other if not wholey eliminate other scenarios other than the desired one.
At 100 microns, as we are trying to accelerate or recirculate the deuterons they crashing into stuff at every turn and we never achieve the potential energy of the full drop between grids. NOT EVEN A FRACTION OF IT! This is sort of an advanced and interesting, focused glow discharge.
At lower pressures the mean free path is up while our gas density is still decent, thus, still affording lots of ionization opportunities. We are still crashing and losing some of our deuterons to elastic collisions, but enough are making it to do fusion.
At the "sweet spot" we have an ideal balance between lots of gas atoms to work with and a more than adequate mean free path to let an optimized number of deuterons fall through the full potential (attaining fusion energy) and, if they don't collide and fuse on the first pass through the poissor, then they have a moderately good chance of a return trip. When this occurs, the star mode needle like beams are seen reaching virtually touching the outer grid region.
ION GUN SYSTEMS:
These are the plus ultra systems of the old Farnsworth team days. In this scenario the chamber is pumped to very deep vacuums of 10E-8 torr or more and never back filled at all!!!!! the vacuum is so deep that the mean free path in a 6" diameter sphere is MILES!!!! The gas is introduced into the negatively biased ion guns and a dispenser cathode heats to produce electrons which ionize virtually all the deuterium gas intoduced. This beam exits the gun as virtually 100% high speed deuterons AT THE OUTER GRID!!! Thus 100% of the deuterons are accelerated to the full fusion energy and enter the inner grid region AT FUSION ENERGY. This allows for incredibly rich and moderately efficient fusion energy production (still not over unity though).
The limitation is that the system must be carefully differentially pumped which really is a feat in and of itself. Without differential pumping the ion gunned system is still orders of magnitude better than the simple fusor we make. As the mean fre path is miles, recirulation is at a theoretical maximum, though in a gunned system, this is redundant.
It is real important to understand all of these aspects of the fusor, and as I have said, read up on ionized gases, vacuum technology, etc. You have to OWN certain concepts at the GUT LEVEL to really be an effective experimenter and not just be able to regurgitate facts as a school boy. Nothing teaches this better than by the DOING.