Diffussion cloud chamber

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Rapp Instruments
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Real name: Thomas Rapp
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Diffussion cloud chamber

Post by Rapp Instruments »

hi,
today I reactivated my old diffussion cloud chamber.The chamber is cooled with peltier elements which are cooled by flowing water. It reach a bottom temperature of about minus 25 °C. The vapour medium is propanol which is circulated by a small peristalic pump for extended time use without refilling. the clearing field of ~ 800 V is generated by a small inverter. The chamber is iluminated by a bar with 25 white light leds all all is powered by a supply borrowed from a personal computer.
I tested the chamber with radon gas which I got from the air above a gas laterne mantle. The Rd 220 decays with a halftime of 56 sec to Po 216 which decays with a halftime of only 0.15 sec. Because of this there are seen sometimes two tracks.
I think if I Iine the chamber with PE sheets and disolve some borid acid in the alhohol to get boric acid trimethyl ester in the chamber vapor it should be a useable neutron detector. You get a big sensible area by the PE sheets, and even bigger sensible volume if the use of boric acid trimethyl ester works. You can see neutron events, unaffected by electrical noise, the discrimination of x-ray back ground is easy.
I think I will try the use the chamber with a small dense plasma focus device

Thomas
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chamber2.jpg
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Richard Hull
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Re: Diffussion cloud chamber

Post by Richard Hull »

Very nice setup. The use of cloud chambers, as such, is almost non-existent in today's nuclear physics world. Amateurs could learn a lot from their construction and use.

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
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Carl Willis
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Re: Diffussion cloud chamber

Post by Carl Willis »

Nice project Thomas.

The methyl borate idea is interesting...I can just imagine the big brushy bow-tie track from the exploding boron nucleus. Unfortunately it would probably be hard to get a significant partial pressure of methyl borate in the chamber and the neutron signature would still likely consist mostly of recoil tracks.

In the two cloud chambers I've made (conventional dry ice cooled diffusion types) I have had best results with methyl alcohol, sold here in the US as "Heet" in the auto parts stores.

-Carl
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Rapp Instruments
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Joined: Mon Mar 23, 2009 7:22 pm
Real name: Thomas Rapp
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Re: Diffussion cloud chamber

Post by Rapp Instruments »

Hi Carl,
the vapour pressure of methyl borat should be 182 mBar (25°C), this of propanol 43 mBar (20°C) so I think one can reach a rather high content of C3H9BO3 in the chamber atmosphere. But I don't know anything about yield of the reaction of boric acid and propanol. Perhaps the reaction works better with methyl alkohol. When I started to build cloud chambers some years ago I made experiments with methyl-,ethyl- and propylalkohol. I didn't found any significant difference between the three alcohols so I normaly use propylalkohol because it's here in germany easier to get then methylalkohol and much cheaper than ethylalkohol.
My "dense plasma focus" is nearly ready and I think the next week I can do the first shots. I have a fast discharge capacitor with 20 kV 1µF (200 J). That not to much but I think some neutrons should be released, at least I should be able to detect some X-rays in the chamber.

Thomas
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