FAQ - Neutron-detection videos

If you have a question about this topic, the answer is probably in here!
Frank Sanns
Site Admin
Posts: 2119
Joined: Fri Jun 14, 2002 2:26 pm
Real name: Frank Sanns

Re: FAQ - Neutron-detection videos

Post by Frank Sanns »

Wax and HDPE should be essentially identical since compositionally they are the same.

PVC is baaaaaddd. Cross section of chlorine will suck up as much as 30% of the neutrons.

Frank
Achiever's madness; when enough is still not enough. ---FS
We have to stop looking at the world through our physical eyes. The universe is NOT what we see. It is the quantum world that is real. The rest is just an electron illusion. ---FS
User avatar
Doug Coulter
Posts: 1312
Joined: Sun May 27, 2007 3:18 pm
Real name: Doug Coulter
Location: Floyd, VA, USA
Contact:

Re: FAQ - Neutron-detection videos

Post by Doug Coulter »

Thanks, Frank,
I'd used some for my silver activation neutron oven, replaced it today with HDPE, betcha my silver gets hotter now, I'll test on the next run.
Why guess when you can know? Measure!
User avatar
Carl Willis
Posts: 2841
Joined: Thu Jul 26, 2001 7:33 pm
Real name: Carl Willis
Location: Albuquerque, New Mexico, USA
Contact:

Re: FAQ - Neutron-detection videos

Post by Carl Willis »

I appreciate the encouragement and am glad to hear that some people enjoyed these videos. I will make some more as time permits. Thanks, Richard, for bestowing the "FAQ" honors on this humble contribution.

Frank, to answer your question about moderators, the common moderators that will produce the highest fluxes of thermal and resonance neutrons are those with a high density of H-1: HDPE, water, wax. Other moderators like D2O, Be, graphite have superlative overall neutron economy because of low capture cross-section, but they can't counteract the geometric attenuation of the neutrons as quickly as H-1 because of the lower fractional energy loss in elastic scattering. For this kind of experiment, the light-hydrogen moderator materials are practically the best. Oxygen is lossy for fast neutrons, so the hydrocarbons fare better than water by a modest margin even if their density is lower. This is probably not so true for fusor neutrons at 2.4 MeV as it is for the fast flux from an AmBe source.

-Carl
Carl Willis
http://carlwillis.wordpress.com/
TEL: +1-505-412-3277
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: FAQ - Neutron-detection videos

Post by Richard Hull »

I should not have to bestow FAQ as an honor.

Anyone that creates a purely informational posting that explains in some detail an erudite point which seems to constantly ellict continuously asked questions, needs to place the FAQ prefix on their post.

Such an author should be prepared to be corrected in critique by anyone bringing up errors or who notes that an addition of an unmentioned point might improve the FAQ.

If the error is of a major nature, or the author realizes that an additional point so mentioned would enhance his original, he should edit the original to correct the error or add additional points brought up in replies that he feels are important.

Do not let errors or omissions in the original FAQ stand and just admit the error in the eighth reply down. Correct the original FAQ as that is what a newb will see and read in a future search. In short, get you original FAQ perfect or as near as possible based on helpful comments in replies.

The above are my rules for me and my FAQs. They might be good ground rules in future for anyone so bold as to use the FAQ in front of their major, contributional magnum opus on a topic.

Do not be afraid to use the FAQ prefix if you have condensed a key point in fusor work, radiation detection, etc. FAQ is not an honor to bestowed upon the poster, but a gift bestowed upon future curious fusioneers by its author with contributed corrections and ammendments by its replies from other knowledable contributors.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Carl Willis
Posts: 2841
Joined: Thu Jul 26, 2001 7:33 pm
Real name: Carl Willis
Location: Albuquerque, New Mexico, USA
Contact:

Re: FAQ - Neutron-detection videos - another one

Post by Carl Willis »

http://www.youtube.com/watch?v=ng6NOH8S7Bk

This video illustrates an activation experiment in which Mn-56 is made in a sample of manganese dioxide, then detected by scintillation spectroscopy. The neutron source is my little AmBe source, but the principles apply to fusor-based neutron activation as well. Both the gamma energy spectrum and the time rate of decay are used to positively confirm the presence of significant Mn-56 in the irradiated sample. Brief mention is made of the importance of moderating fast neutrons for activation. A "neutron oven" is shown to effect this. The detector, NIM-based signal chain, MCA, and data acquisition on my computer are all described. The time and energy data are simultaneously collected into different parts of the MCA's memory bank, for both the irradiated and the background MnO2 samples. At the end of the video, processed data is discussed. That same data is in the figures below.

Pacing is fast (in order to keep within YouTube's 10-minute time limit), at the expense of detail. So I'm happy to address any details that were glossed over in the movie itself.

Bon appetit!

-Carl
Carl Willis
http://carlwillis.wordpress.com/
TEL: +1-505-412-3277
User avatar
Steven Sesselmann
Posts: 2127
Joined: Wed Aug 10, 2005 9:50 pm
Real name: Steven Sesselmann
Location: Sydney - Australia
Contact:

Re: FAQ - Neutron-detection videos - another one

Post by Steven Sesselmann »

Carl,

Once again, an excellent and informative video. I think it deserves a new post.

FAQ - Neutron Activation and Gamma Spectrometry

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
User avatar
Chris Bradley
Posts: 2930
Joined: Fri May 02, 2008 7:05 am
Real name:

Re: FAQ - Neutron-detection videos - another one

Post by Chris Bradley »

Thanks Carl. All lovely work and well presented.

It makes me wish I lived in the US where I might be able to get this kit. Never seen a NIModule here in the UK to buy, we don't get the standard of surplus stores and hamfests here. I'll have to make do with just watching you do it instead!!..

Quicky question; was the half-life count the total net counts, and if so (or if not, vice versa) do you think it could be improved by using only the counts over time as detected around the peak?
User avatar
Carl Willis
Posts: 2841
Joined: Thu Jul 26, 2001 7:33 pm
Real name: Carl Willis
Location: Albuquerque, New Mexico, USA
Contact:

Re: FAQ - Neutron-detection videos - another one

Post by Carl Willis »

Hi Chris,

The time spectrum is collected through an SCA that coarsely windows the 850-keV gamma peak, in order to improve the statistics as you suggest.

With the ADC in the bin, it's quite easy to use the timing SCA in this manner without calibration. I take the bipolar output of the delay-line amp to the SCA with a very short cable. I take the fast negative output of the SCA to the coincidence gate on the ADC with a very short cable. Then, the unipolar output from the delay-line amp is sent to the input of the ADC over a long cable so that it arrives by the time the gate can be opened. In this manner I can graphically adjust the window of the SCA relative to my calibration pulse-height spectrum and get it in exactly the right place. To take counts on the MCS, the SCA output to the ADC coincidence gate is then simply moved to the input on the MCS.

-Carl
Carl Willis
http://carlwillis.wordpress.com/
TEL: +1-505-412-3277
User avatar
Mike Beauford
Posts: 419
Joined: Wed Apr 25, 2007 2:24 pm
Real name:
Location: Morton Grove, IL

Re: FAQ - Neutron-detection videos - another one

Post by Mike Beauford »

Hi Carl,

Another great video Carl, if I were you I'd start to think about writing a book about this stuff. I suspect you won't make a ton of money, but I think it will do wonders for your career.

Mike Beauford
Mike Beauford
richnormand
Posts: 307
Joined: Sat Aug 27, 2005 8:30 am
Real name: rich normand

Re: FAQ - Neutron-detection videos

Post by richnormand »

As your videos are on youtube is there an easy way to get you to either post them on this site or have a way to download them. They are quite good and I would much like to have them burned on a CD than see them disappear in the future. If you do consider downloadable version make sure you embed a visible watermark on them so your copyright is safe.
Nice work Carl.
DaveC
Posts: 2346
Joined: Sat Jun 30, 2001 1:13 am
Real name:

Re: FAQ - Neutron-detection videos - another one

Post by DaveC »

Carl -

These are quite good. You have a clear and unhurried style of explaining that's very easy to follow.

These make a very useful addition to all the basic information that's on the site.

Thanks for taking the effort to organize them and putting them up for all to see.


Dave Cooper
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: FAQ - Neutron-detection videos - another one

Post by Richard Hull »

More superb work by a superb researcher and and sharer of good info.

Another three or four atta' boys for Carl.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
hjerald1
Posts: 54
Joined: Mon Feb 25, 2008 11:28 am
Real name:

Re: FAQ - Neutron-detection videos

Post by hjerald1 »

Interesting videos Carl. Thanks for posing them.
Your radiomanganese clip reminds me of an anecdote from the 1980s when I was doing neutron activation analysis of some geological samples using the U of Utah research reactor. I was handling the irradiated polyethylene sample capsules and transferring them into the gamma ray spectrometer with my bare hands. Perhaps not the optimal technique but then those were the good old days.
Jerry
User avatar
Steven Sesselmann
Posts: 2127
Joined: Wed Aug 10, 2005 9:50 pm
Real name: Steven Sesselmann
Location: Sydney - Australia
Contact:

Re: FAQ - Neutron-detection videos

Post by Steven Sesselmann »

Carl,

I am trying to replicate the setup that you are doing on the video. I have the identical He3 tube with a Cremat charge sensitive preamp, but unfortunately I don't have a hot gamma source or a sealed neutron source.

I have the He3 tube connected to the preamp, and set to 1500V, and the output from the preamp plugged into my oscilloscope, and I get absolutely nothing but a straight line.

Can this be right?

Shouldn't I at least get some slight background clicks?

The amp seems to work, because if I just move my finger close to the HV connection the scope immediately shows a strong signal.

So my question....Is it likely that the tube is dead, or is this normal?

A tiny neutron source would have been terrific.

Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
User avatar
Doug Coulter
Posts: 1312
Joined: Sun May 27, 2007 3:18 pm
Real name: Doug Coulter
Location: Floyd, VA, USA
Contact:

Re: FAQ - Neutron-detection videos

Post by Doug Coulter »

You should at least see some big ones from cosmic rays....something isn't right.
Why guess when you can know? Measure!
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: FAQ - Neutron-detection videos

Post by Richard Hull »

Not a lot to go on here except the preamp seems to be on.

What is the value and voltage standoff of the input capacitor?

The tube might be dead if it is surplus. Does it have a pressure indication on the label?
What about a voltage range or figure on the label?

You sort of have to have at least a nice hot piece of U ore!

I hope your scope is a DSO so that you can single shot capture any large cosmics. If not, then you might miss them on an old analog scope in auto roll mode.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
User avatar
Richard Hull
Moderator
Posts: 14991
Joined: Fri Jun 15, 2001 9:44 am
Real name: Richard Hull

Re: FAQ - Neutron-detection videos

Post by Richard Hull »

Polyethylene is the overall best moderator for the amateur and a, "right on its butt", second would be Paraffin wax which is much easier to obtain, but is a fire hazard in the amounts needed. There is no nearby third choice compared to these two.

You should really strive for the P.E. at a local plastics distributor. Some vendors are happy to sell, at low cost, odd ball cutoff chunks that are no longer of much value. thiese can be stacked and mounded up to make all manner of useful and efficient neutron ovens, caves and howitzers.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Post Reply

Return to “FAQs: Neutron - Radiation Detection”