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: This weekend's work
Date: Feb 15, 10:20 am
Poster: Richard Hull
On Feb 15, 10:20 am, Richard Hull wrote:
Fusor III has now hit the record breaking level of 21KV at 4-5 ma this weekend in a series of control tests prior to D2 introduction. Good scientific controls are needed to verify full power operation and establish non-D2 radiation type and levels.
Fusor III has a design limit of 25KV and I am close to that now. The system hissed constantly and arc'd over 3" at the transformer just once. (probably kick back from the pulsing nature of ths system at odd moments) I solved this with judicious application of hot glue at corona points. From here on there was no ozone and no hissing.
For those who have never fired up a fusor, the attainment of 21kv actually across the chamber, (notjust across the power supply output terminal), is a real thoughy! It requires tight control of the pressure and about 1/2 hour of chamber pre- conditioning at lower voltage. This is especially true if one is using second hand, dirty and lame stuff like I am.
The star was a very sharp, needle pointed and faint affair at these levels. This was obviously due to the submicron pressure levels, the result of weeks of pumping, ion cleaning and never opening the system up to air. (Not since Jan 8th) The valved off system will hold to 3 microns over 4 days.
I had a gang of instruments surrounding the system. I carefully noted that at no time did the air filled system, (submicron), ever make the neutron counter count above background up to 20kv.
At no time did either a geiger counter or ionization type victoreen X-ray survey meter show any indication above background at point contact with the 316 SS shell of the fusor chamber. This was over the full range of voltage to 21KV. This is great as the fast neutron detector will detect gamma and X-ray photons, but these can be easily and totally ellimenated by pulse height discrimation. This result now makes such discrimination pointless with this system and at this voltage level. Still, it is nice to know that this fusor is totally impervisous to X-radiation up to 21 KV. (SS .090 walls stopping it).
I did note that the small camera pyrex viewport started spewing X-rays in a narrow beam at about 17KV with the gieger counter counting about 1500 counts/minute. (well above the 30 CPM background). At 21KV the counter's mica windowed tube was roaring at 8000-10,000 cpm when placed in front of the viewport. Also interesting was the fact that under 3mr/hr of actual xradiation registered on the victoreen x-ray survey meter at 21kv while the thin aluminized mylar window was in contact with the viewport. These x-rays are very soft indeed.
I was a little concerned for my CCD video camera has its "eyeball" in point contact with the pyrex glass. The video is totally unaffected by the x-ray blast. I am assuming its lens system intercepts the bulk of the soft rays leaving the chamber. CCDs are very susceptable to having their delicate cell charges screwed with by radiation.
This again is great as all I need to do is keep any mesurement devices isolated from the narrow port beam of x-rays. The rays require no shielding and the device is harmless from an x-ray standpoint over virtually its entire surface area through 21kv!
The neuts will blow through the steel like it isn't even there! Thus, for up to 21KV all I will need will be a boron shield system which covers the area presented by my body. A fish tank or the like with water which has been supersaturated with borax should do the trick.
- Re: This weekend's work - Douglas R. Fix Feb 17, 10:03 pm