Cloud Chamber Efficiency

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
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Eldarion
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Cloud Chamber Efficiency

Post by Eldarion » Sun Feb 01, 2009 4:02 am

How efficient would a cloud chamber b in neutron detection. This is about the cheapest way that I can think of for detecting neutrons, but I do not know how well it would detect neutron radiation. Would it be able to effectively detect neutrons from a fusor operating in the 10-15KV range? I once built one to detect strong gamma rays from cosmic radiation, and it was pretty effective in tracking those, as well as costing me less than $20 to build.

Thank you all for your continued help.

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Carl Willis
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Re: Cloud Chamber Efficiency

Post by Carl Willis » Sun Feb 01, 2009 5:02 am

Hi Nelson,

>How efficient would a cloud chamber b [sic]

This is too open-ended to answer. To get started, you would need to know, or decide upon, what neutron-detecting reaction you'll be exploiting (neutrons themselves leave no tracks because they're uncharged); the fill-gas mixture and pressure in the chamber; the active volume of the chamber; and where in relation to the fusor the chamber would be situated. Once you come up with answers to those, you can calculate almost trivially what the reaction rate in the chamber will be. There are some other interesting effects to think about later on that can impact the apparent efficiency.

By the way...did you search this forum for "cloud chamber"? There are a couple good threads. Did you see Jon Rosenstiel's posts?

-Carl
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Dan Tibbets
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Re: Cloud Chamber Efficiency

Post by Dan Tibbets » Mon Feb 02, 2009 1:11 am

A link to a cloud chamber used with a Fusor. I'm uncertain of the author. It may be Jon Rosenstiel.

http://www.earthtech.org/experiments/fusor/cloud.html

Dan Tibbets

Eldarion
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Re: Cloud Chamber Efficiency

Post by Eldarion » Mon Feb 02, 2009 2:01 pm

I have looked at the posts for cloud chambers, but none of them mention if if is good enough to detect fusion from a fusor operating at around the 15,000 volt range.

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Richard Hull
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Re: Cloud Chamber Efficiency

Post by Richard Hull » Mon Feb 02, 2009 4:16 pm

At 15KV there isn't much fusion.

The range, fusor-to-chamber, is critical. To say the least, efficiency will be terrible and separating neutrons from cosmics will be tough. You will tend to detect protons as resultants of neutrons. Neutrons can't be seen in a cloud chamber.

It would possibly be an indicator of fusion if the effort was well done, but little to no quantitative data could be gleaned without careful setup and recording techniques in place.

As Carl notes there can be interesting side reactions.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Carl Willis
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Re: Cloud Chamber Efficiency

Post by Carl Willis » Mon Feb 02, 2009 6:54 pm

>none of them mention if if is good enough to detect fusion from a fusor operating at around the 15,000 volt range.

Naturally, it's up to you to figure out if a detection technique is suited to your particular circumstances. You can't expect to be spoon-fed a yes-or-no answer on something like this.

In theory any detector is good enough to detect fusion at 15 kV (or 1 kV, or 1 V)--the important variable is how much time you need to obtain statistically-meaningful results. A detector with poor efficiency and poor selectivity against background radiations may require weeks of counting time to indicate the presence of fusion neutrons, versus a detector with good efficiency and good selectivity that may give you the same result in minutes. The concepts, data, and calculations for this cloud chamber idea are not beyond anyone and I think you should give them a try.

-Carl
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Re: Cloud Chamber Efficiency

Post by Eldarion » Mon Feb 02, 2009 11:39 pm

So what you are saying is that unless operating at higher voltages, this should only be used as a secondary method of detection? Sorry for earlier miscommunications, but through proton recoil, it is indirectly measuring neutrons. Although it does not detect the neutrons itself, it detects the presence of them. So, effectively it does tell you the neutrons are there even though it cannot detect the neutrons them self.

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Carl Willis
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Re: Cloud Chamber Efficiency

Post by Carl Willis » Tue Feb 03, 2009 6:02 am

Hi Nelson,

I suspect (but have no way of knowing for sure) that when you do some calculations--proton density, chamber volume, neutron flux, scattering cross-section--pertaining to your chamber idea, you will come to the conclusion that it is a very inefficient detector with hard-to-interpret results.

You still have to do the math yourself and decide if it's the right tradeoff for $20, or if you'd rather pursue the more conventional but pricier options of bubble dosimeters or proportional tubes.

-Carl
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