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 Counter Q's
Date: Oct 25, 12:17 pm
Poster: Carl Willis

On Oct 25, 12:17 pm, Carl Willis wrote:

>This is probably the reset button. On long time >constant ranges, this should quickly sent the >meter needle to the zero pin by discharging the >integrating capacitor in the metering circuit. RH

Thanks for the pointer, that is indeed what it does.

>Most fast neutron counters count around 1 count >per 2-3 minutes. (night time) I have 4 of >them. You may have a bad tube or the >discriminator level set too high. Also, never >use a counter until it has stabilized for about >5 minutes. It is normal for a freshly turned on >counter to maybe give 3 clicks/min when first >turned on. A fairly intense gamma source placed >near the counter should not register at all!!!
>Richard Hull

This is a real interesting point- to let the thing stabilize, and I'm glad you mentioned it. When we turned it on, it would chirp several times per minute and then seem to stop after a couple minutes with only a sporadic chirp. I thought we had a cable problem, and I put in another (rather shabby built-on-the-spot) test cable, during which it kept up doing a count every twenty sec's or so. But this might just have been noise. The original cable is fine in fact, and in putting it back we see a chirp every couple min, AFTER waiting about five minutes. I'll run the chirper output to a LabView interfaced meter to get data, and I'll probably start keeping backgroud counts right now so I get familiar with daily cycles, normal patterns, whatnot. Tx for the help! -Carl