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SNM-9 neutron detector for A multipactor.

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LAN_403

MArked One

Mon Apr 25 2011, 10:49AM

Registered Member #3688 Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38

Greetings.

I am looking for a neutron detector for my upcoming multipactor rig. I have recently found a seller offering SNM-9 USSR neutron counters.
I'm looking for advice: how do I do this for the lowest amount of cash? Does anyone have any personal experience they'd like to share about using homemade cloud chambers, or scintillators perhaps? I understand that the question is a little vague, but I have practically no way of predicting the neutron yield (or if there will even be a neutron yield).

Kind Regards,
Ivan Kozlov.

Ash Small

Mon Apr 25 2011, 11:12AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

You may find this site useful:

(But they don't like questions that aren't related to fusors, though.)

EDIT: Isn't a fusor a 'multi-pacting diode'?

Proud Mary

Mon Apr 25 2011, 12:28PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

MArked One wrote ...

Greetings.

I am looking for a neutron detector for my upcoming multipactor rig. I have recently found a seller offering SNM-9 USSR neutron counters.
I'm looking for advice: how do I do this for the lowest amount of cash? Does anyone have any personal experience they'd like to share about using homemade cloud chambers, or scintillators perhaps? I understand that the question is a little vague, but I have practically no way of predicting the neutron yield (or if there will even be a neutron yield).

Kind Regards,
Ivan Kozlov.

CHM9 datasheet

1303735375 543 FT0 Chm 9 Neutron Detector A

MArked One

Mon Apr 25 2011, 12:49PM

Registered Member #3688 Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38

Thank you for the replies.
@ Ash Small: Understood, will inquire there as well.
@ Proud Mary: thank you very much for the datasheet. It provides everything except for the actual neutron sensitivity. (for every tube except for the SNM-9 it is 15%, but the SNM-9 does not have the sensitivity listed.). On a slightly different note, would you like a translated version?

in my understanding, the tube is a corona measuring device: the neutron pulses are superimposed upon the constant corona signal. Am I correct in assuming that I will only need to implement ordinary GM circuitry plus a corona signal filter? On a slightly different note, how does one determine the neutron attentuation through a moderator? (the tube only detects thermalized neutrons)

Proud Mary

Mon Apr 25 2011, 01:17PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

MArked One wrote ...

@ Proud Mary: thank you very much for the datasheet. It provides everything except for the actual neutron sensitivity.

Wakey wakey!

I have edited/replaced my original CHM9 datasheet post because I was concerned over its authenticity - the addition of measurements in inches to the table made it clear that the information had been prepared post-CCCP for the purpose of selling the tubes outside Russia. I have replaced it with the original CHM9 datasheet without the added material, which seems to me incorrect.

Don't you think it might be a good idea to study some basic books on neutron dosimetry before you go any further with your 'multipactor' thingy?

An experiment without measurement is no more than a theatrical spectacle, a circus event, and perhaps even a dangerous or illegal one for all I know about neutron sources.

MArked One

Mon Apr 25 2011, 05:26PM

Registered Member #3688 Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38

Thanks for correcting me.
I was referring to the "ÐµÑ„Ñ„ÐµÐºÑ‚Ð¸Ð²Ð½Ð¾ÑÑŒÑ‚ Ðº Ñ‚ÐµÐ¿Ð»Ð¾Ð²Ñ‹Ð¼ Ð½ÐµÐ¹Ñ‚Ñ€Ð¾Ð½Ð°Ð¼" part of the modified datasheet. It seemed rather large to begin with.
To be true, the neutron dosimetry is probably the only aspect of the device I didn't properly study: I assumed (rather stupidly) that it would be the simple matter of "applying the correct voltage and counting the pulses". Measuring the neutron flux (if any) is one of the goals of the experiment, and I assure you that I have thoroughly researched the safety hazards.

In any case, do you have any advice on practical use of the tube?

Proud Mary

Mon Apr 25 2011, 06:32PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

MArked One wrote ...

Thanks for correcting me.
I was referring to the "ÐµÑ„Ñ„ÐµÐºÑ‚Ð¸Ð²Ð½Ð¾ÑÑŒÑ‚ Ðº Ñ‚ÐµÐ¿Ð»Ð¾Ð²Ñ‹Ð¼ Ð½ÐµÐ¹Ñ‚Ñ€Ð¾Ð½Ð°Ð¼" part of the modified datasheet. It seemed rather large to begin with.
To be true, the neutron dosimetry is probably the only aspect of the device I didn't properly study: I assumed (rather stupidly) that it would be the simple matter of "applying the correct voltage and counting the pulses". Measuring the neutron flux (if any) is one of the goals of the experiment, and I assure you that I have thoroughly researched the safety hazards.

In any case, do you have any advice on practical use of the tube?

First, Ivan, I must say that I have no practical experience of neutron counting, and have only a little knowledge about it.

But we can still be certain that this tube will also be sensitive to X-rays produced by your 'multipactor,' so we have to find a way to discriminate against them - a traditional problem in neutron dosimetry.

An easy way to do this will be by differential counting using two tubes. One of these tubes should be placed inside a Pb shield, and the other tube left unshielded. X-rays will be stopped by the Pb, giving a large difference signal between the tubes, but neutrons will produce a much smaller difference signal as the Pb will stop them only a little..

If you Google neutron gamma discrimination you will find a great pile of scientific writing on this subject.

I found this article to give a good introduction to neutron detection for someone like me who knows little about it:

Good luck with it all!

Stella

MArked One

Thu Apr 28 2011, 09:21AM

Registered Member #3688 Joined: Mon Feb 14 2011, 07:39PM
Location: Europe
Posts: 38

Thank you for your help.

To discriminate between gamma and neutrons, I will first run the device with hydrogen for 30 minutes (about half of the estimated grid lifetime), take the average of the radiation, and fill the chamber with deuterium and substract the x-rays and background.

Does that sound plausible? Will there be a large discreptancy between the radiation emmisions of a hydrogen and a deuterium plasma? (disregarding neutron flux)

Proud Mary

Thu Apr 28 2011, 09:37AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

MArked One wrote ...

Thank you for your help.

To discriminate between gamma and neutrons, I will first run the device with hydrogen for 30 minutes (about half of the estimated grid lifetime), take the average of the radiation, and fill the chamber with deuterium and substract the x-rays and background.

Does that sound plausible? Will there be a large discreptancy between the radiation emmisions of a hydrogen and a deuterium plasma? (disregarding neutron flux)

You'll have to ask someone with recent practical experience of this type of neutron generator.

Anything I said would be a guess.

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