Reuter Stokes Proportional Counter

[9a3daa]

Respect.

I have Reuter Stokes Proportional Counter - Model: RS-P7-0805-127
Length: 20 cm with HN connector. Sensitive length: 16 cm Diameter: 2.5 cm

Writes this: Proportional Counter
Fill gas Ar (Argon)
Pressure: 23 cm Hg (0.3Bar)
Max.Volt 1200

I contacted GE and they told me this:

The part RS-P7-0805-127 would be a B-10 lined proportional counter, filled with ~0.8bar of Argon as quench gas. According to our files, this detector was made in 1976.

The reason why I was puzzled by your request is that this particular detector is not designed for gamma radiation. On the contrary, it is a neutron detector, with a very good gamma discrimination.

Question: How can discriminate gamma, and measure neutrons?
On my instrument I have only threshold potentiometer.
Now only receives pulses from gamma background (80-100CPM)

[Richard Hull]

Interesting. I have never seen this type of boron lined tube. I do know that the bias voltage is critical and is often below 900 volts and that a good pre-amp is needed with careful setting of the discriminator. Boron lined tubes can be great, but a simple instrument is not going to work them correctly.

You may have to assemble a NIM setup and make your own pre-amp or cobble up a system from scratch. I have no doubt that the tube is a nice find and worth all the effort that it would take to make it count neutrons.

A good neutron source would be nice to have in working with discriminating this tube.

Richard Hull

[Tyler Christensen]

I had pretty good luck getting B-10 tubes to work in the past.

Like Richard said, you need to have voltage control in addition to discrimination level control. At a certain voltage, the gamma level was vastly below that of neutrons. 50V lower, there was nothing and 50V higher the gamma signal would be huge and way above that of neutrons.

Pretty much all I did to set it up was set the discrimination at a fairly low setting and turn up the voltage until gamma set it off. Then back it down about 50V, and then it was good to measure neutrons.

Of course, if you have manufacturer suggested voltages just use them and set the discriminator to cut out gamma. Might still require some tweaking of the voltage, though.

[9a3daa]

Gas is not B-10. Its filled with Argon.
And written: 1200V max

And tube is bad. Has a narrow plateau. When the voltage is below 1150V - no pulses.
When the voltage is above 1250V goes to saturation.
When the voltage is exactly 1200V gamma background radiation is 80 - 100CPM

And sometimes alone knows to stop giving impulses @ 1200V.

Once this tube is 20 years ago worked at +150 degrees Celsius
It was a measure of the thickness of the asphalt, with powerful Cobalt 60 source.

I think the tube is dead, because today sometimes will not giving impulses @ 1200V.


And I have AmBe neutron source - 60uCi

[Chris Bradley]

Arni,

There is tons of stuff about this in these forums, which will explain what you are seeing with the tube.

Rather than ask a question, try helping yourself first and read.

But, well, if you are now sure this means the tube is dead, you can send it to me if you like, and I'll pay you $5 on top of postage, then I'll 'recycle' it for you properly. You don't want boron getting just anywhere now, do you?

The introduction says to post an intro on yourself. We hope to see that soon.

[Richard Hull]

Tyler gave good info as the voice of experience. The voltage to detect neutrons is no where near 1200 volts. You need to put a thermal neutron source near the tube or put the tube in a moderator jacket and use a fast neutron source. Next, using a rather high gain, high impedance preamp, look at its output with an oscilloscope as you raise the voltage from about 700 volts.

At some point, you will see the neutron pulses appear. If you keep advancing the voltage higher, you will see a flood of pulses. Back off the voltage until you see just the neutron pulses again and leave the voltage there. To double check, remove the neutron source. The pulses should virtually stop.

Richard Hull

[9a3daa]

No! Its NOT B-10 gas - Filled with Argon - see picture

[9a3daa]

Is 60uCi Ambe neutron source enough to get impulses from preamplifier?

[Chris Bradley]

Yeah, we know that Arni. No-one's said otherwise. The inside is lined with boron, that's how B-10 tubes are made .... and your next outburst is ...?

[Chris Bradley]

From just 60uCi of Am? .. I can't see how you'll measure that over background with a little B-10 tube like this. [...YES... its ARGON filled... we know!!!]

Read the other threads, you'll see how to estimate the n rate. So, again to say.. good idea to read the threads first, than ask questions without reading.

[9a3daa]

As far as I know - according to my calculations - a 60uCi AmBe give flux of 30n/s

Of course, I'll have a little look at the other threads.

[Carl Willis]

I don't see anyone disagreeing with you that this is a B-10 LINED tube filled with argon.

There is ample information about using these kinds of tubes in our archives. Based on your description of your testing so far I cannot conjecture about the tube's condition. I think Tyler gave you good advice about testing it, but I will add that an MCA is very helpful. There are example pulse-height spectra from neutron capture in B-lined tubes in this forum.

A 60-microcurie AmBe source of decent home construction probably emits about 10 n / sec. That's detectable over counting intervals of an hour or more perhaps, but extremely weak and not likely to be helpful in testing your tube.

-Carl

[Richard Hull]

Usually you would need a 300uCi source or better for easy, obvious counting. Using a 1mCi source would be just about ideal for "no statisitics" or long counting regimes. This is given that the boron lined tubes are not as efficient as a 3He tube which is capable of working with a god deal weaker source.

Richard Hull

[9a3daa]

One more question:
Why are you sure that the my tube is B-10 lined?
Why this does not written on the nameplate?

I want to be 100% sure that this neutron detector.

[Tyler Christensen]

Because GE told you it is...

"The part RS-P7-0805-127 would be a B-10 lined proportional counter, filled with ~0.8bar of Argon as quench gas. According to our files, this detector was made in 1976."

[Carl Willis]

Your first message quotes a response from GE Reuter Stokes to your own inquiry:

>"The part RS-P7-0805-127 would be a B-10 lined proportional counter."

That's the tube's manufacturer telling you what it is. There is no reason to suspect it's inaccurate, and there's nobody here who can be more authoritative on the subject.

-Carl

[9a3daa]

Thank you very much all!

Soon I'm going to institute in my town for the equipment- and I'll get you the results.

[9a3daa]

Why GE are we told me that is ~ 0.8bar - and on my tube writes Pressure: 23 cm Hg

And 23 cm Hg is 0.3bar
How?

[Chris Bradley]

Maybe they told you '-0.8bar', or that the label should've been marked as inches Hg??

...just errors...

Either way, are you saying you doubt all the information the manufacturer of the item then supplies you?

[Carl Willis]

Well, one possibility that's easy to think of is that the person who went to the filing cabinet to look up data on your tube saw a "0.3" on the spec sheet and thought it looked like "0.8". The numbers 3 and 8 look similar. You could always ask them to clarify, if it matters sufficiently to you. The label is more likely to be accurate.

On another matter...please follow the rules regarding an introduction if you intend to keep posting to our forums. We have this rule to cut down on "drive-by" posting and to promote community. Thanks in advance.

-Carl

[9a3daa]

How am I violate the rule?

I'm just politely asking questions.
I was a little confused, and do not know English very well - I use google translator - please have a little understanding.

[Carl Willis]

From the rules:

>2) New members are required to introduce themselves in the "Please Introduce Yourself" forum prior to posting elsewhere on the site.

Thanks,
Carl

[9a3daa]

Am Introduce Yourself

[9a3daa]

GE told me again by email:

Dear Arni,

I apologize for my answer. If the pressure written on the tube is 23cmHg, then it is 0.3bar of Argon. Which strengthen my position that this detector is not design for gamma radiation detection.

At Reuter Stokes, we have more than 56 years’ experience in making nuclear detectors. According to our numbering system, which I attach a copy to this e-mail: RS-P7-0805-127

- RS means that it is a Reuter Stokes detector,
- P7 is a B-10 lined proportional counter
- 08 is the diameter of the detector in 1/8 of an inches,
- 05 is the length of the detector in inches,
- 1 means that the body shell is made of aluminum, and
- 27 is the number of the detector in the series issued.

Now I'm 100% sure that it is a neutron detector.

[9a3daa]

How much thick should be moderator for my detector?
parafin moderator: ________inch
HDPE moderator: ________inch