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, 8:33 am
Poster: Richard Hull

On Oct 25, 8:33 am, Richard Hull wrote:

>Hey Folks with Neutron Counter Experience,
>I got my surplus unit today- it's a ludlum M 12-4 BF3 / polyethylene sphere type. Appears to work, chirping several times per minute due to background. First question: It's got a pushbutton labeled "RES" on the front that I have no clue about. Can anyone tell me its possible function?

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


Second question: I'd like to be able to connect the unit in some fashion to a computerized data logger to look at rates over extended times. Possible output voltage points are: the speaker, which chirps for every count; the meter, which registers the counts; and the tube itself. In this case I will need to use an amplifier and pulse shaping equip. And then there's all the rest of the circuit in the case. Ideas of where to tap into this thing??

I would go for the chirper leads. you will not count fast enough for them to pile up beyond its pulse width.

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