FAQ - Fusor Construction Journey in images from the beginning #3

[Richard Hull]

1997-1998 Fusor II

In late 1997, just before the new year of 1998, I was already constructing Fusor II. This was to be a traveling demo system on a wooden frame with instrumentation and variac, all in a boxed system. I had a great direct drive, Yellow Jacket pump that could pull 6 microns at the head with fresh oil. I would employ a glass bell jar in this system to avoid any out-gassing issues. A good, thick, flat machined aluminum base would allow for a good vacuum seal and act as a large ground on which to mount the outer grid on stand-offs. Once competed in late January of 1998. I was really pleased that at first pump down, I got to 25 microns in under 2 minutes. By late February I was down to 10-15 microns and obtained my first fabulous "star mode". Star mode came as a complete surprise to me as Tom Ligon never mentioned it!! I was stunned! Slowly the vacuum would attain 9 microns and stars were the norm. I would be able to reach extinction at some voltages and currents. A marvelous period of discovery would follow as many principles would show themselves as unique in my experience.

One of the most interesting was the discovery that I could critically adjust the supply to just barely reach extinction. In this state, I would rub a piece of fur on a teflon rod, and as I quickly brought the rod into a fast arc to stop 18-inches short of the fusor II bell jar, the fusor would strike and light up. As it remained frozen at 18-inches, one could yank it away and the fusor would go dark. At once, I understood the link between gas pressure and electrostatic tension in vacuums.

There was much discovery with magnets in and around extinction and the discovery that a rare earth magnet would cause the supply to draw a tremendous amount of current and the grid to heat to red heat. After every application and removal, the pressure would drop a few microns to extinction. This is how an ion pump works. The light came on in my head once again.

With a metal fusor I would never have had this adventure. One thing I learned was that a good deal of reading would now be in order. From May 1998 until late 1998 I did only two things. I read voraciously about about ionized gases, vacuum technology and neutron physics and gathered parts for a beginning at construction of a spherical, stainless steel fusor. I began the machining and welding in October and disassembled fusor II by December. During its one year life span, It taught me more than I might have hoped for. I found that over-driving fusor II to 15kv could locally "spot heat" the glass bell jar at a point and I actually saw a tiny chip break off the inside in one instance. This was frightening and I saw that only a metal fusor would ever fuse.

After looking at the images below, you can move on to my next fusor effort by going here (Fusor III)

viewtopic.php?f=24&t=13053&p=84815#p84815

Below are an equally limited number of images of this demo system that taught me so much.

Richard Hull