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: Neutron Counters and Pressure Gauges
Date: Sep 26, 4:15 pm
Poster: Carl Willis

On Sep 26, 4:15 pm, Carl Willis wrote:

>Which past post has the information on building the neutron counters. I can't seem to find the right one (if you can give me the name of the posting)

Do a "find" for the words neutron, counter, detector, etc. There's not just one post, in fact there are tens of good ones. Just take a few hours to look through...I'm still not done reading the useful posts and I have been doing it for the past two weeks!
>PS, what about Pressure Gauges?

For what? For the deuterium you really don't need a pressure guage, but it's a good indication of how fast you use the gas and what delivery pressure is. Get any old lecture bottle regulator with the CGA 170 fitting (I think that's what it is.) The low-internal-volume regulators with in / out guages sell new for $320 and up.

For high vacuum you have a few options. Thermocouple or Pirani-type guages are cheap and will measure the pressure down to about 1 micron, with a correction factor applied for certain gases that are not air, like deuterium. Ion guages and their circuitry are expensive and measure 10 -4 torr and lower, again with corrections for non-air gases. PIG's (like we have at Guilford) measure down to about 10-5 torr. They have magnets attatched to increase ionization in their discharge volume, and I have yet to find out if having such a magnet near the fusor would badly affect its operation. Capacitive guages are what some folks on the list use. They still directly measure the pressure the molecules exert on a surface, just like a cheap bourdon guage, but they are much more sensitive because of the capacitor measuring technique. Lots of choices...

>Michael Li