Archived - Cloud chamber photos

[Jon Rosenstiel]

Note* I continue to archive these cloud tracks as these represent the operation of probably the least expensive neutron detector the amatuer might construct. It is not a suitable quantitative device but is a superb qualitative one.

For details on Jon's chamber go to


viewtopic.php?f=13&t=5599#p34043

RH


I’ve been working on my cloud chamber photo skills….

Radium daughters (mostly alphas, but some betas too) are being emitted from a piece of sandpaper glued to the face of a small (0.75 x 0.25 inch) wood block. (Visible at the very top of the photos).

There is a lot of detail in some of the images, so I left them full size.

Jon Rosenstiel

[attachment=0]Cloud1.jpg[/attachment][attachment=1]Cloud5.jpg[/attachment][attachment=2]Cloud4.jpg[/attachment][attachment=3]Cloud3.jpg[/attachment][attachment=4]Cloud2.jpg[/attachment]

[Q]

WOW! those are great!

Q

[Frank Sanns]

Really great pictures Jon!

I am curious though of how do you keep the condensation off of your viewing glass? Also, what is the deal with the sandpaper and radiactive emissions? Silicon Carbide does not emit.

Frank S.

[Richard Hull]

Nice images Jon!

I note a couple of beautiful Beta particles on the first image. (thin thready, beady and irregular runs.)

I am assuming a radium daughter on the sand paper is the emitter.

Richard Hull

[Jon Rosenstiel]

I put a camera veiwport (glass) in the top of the chamber and have no problem with condensation there. I'm working on a cloud chamber report; I'll post it in the near future.

Very special sandpaper, Frank. Found only in turn-of-the-century hardware stores!

Actually, see Soddy's "The Interpretation of Radium", first edition (1909), page 192.

Jon Rosenstiel

[Jon Rosenstiel]

Yes, radium daughters. I try to make my posts brief, but appears that I over did it in my original post. I'll correct it.

Jon Rosenstiel

[Carl Willis]

Those are some stunning shots, Jon.

I'm getting inspired to buy the parts needed for a cloud chamber. The grocery here in Los Alamos sells dry ice for a buck a pound...

-Carl

[Richard Hester]

It looks like there was a reaction in picture 4. The two short, dense track branches are a giveaway.

[Richard Hull]

That looks like a rare end of life ionization. It is normal to see an alpha track end in a single, short turn arm. What happens is the particle slows to some velocity where it is deflected elastically due to its near inability to ionize.

Rare is the time that the weak helium nucleus ionizes and shares a decent amount of its energy with a gas atom resulting in two short tracks.

Richard Hull

[Jon Rosenstiel]

Re: picture #4. My understanding of what happened is:

The alpha particle (helium nucleus) has struck an oxygen nucleus. The long arm of the collision is the deflected alpha. The short arm is the recoiling oxygen nucleus.

Jon Rosenstiel

[Richard Hull]

Why an oxygen nucleus? Nitrogen is far more likely. It is obvious that the alpha was nearly spent. (similar tracks nearby end here). The track just to the right is a typical end track with the little hook on the end.

For those not in the know, the other puffy tracks are old alpha tracks that have diffused like a jet contrails. The one real long track has got to be from Radium C' (Po214) and is nearly 8mev in energy!

Also, the diffused tracks can be periodically erased by a clearing field of high potential. See Jon's excellent presentation on his modified chamber in the radiation forum.

Jon, I assume that the wires I see in the image are for the clearing field or are they optical gridwork reference indicators?

Richard Hull

[Richard Hester]

On second thought, I must agree with Mr. Hull. Since the fork is at the end of a long track, it is much more likely to be a scattering and ionization event than the a, N14 reaction. With patience or a more intense source, though, one of those might show up.

[Richard Hull]

I am relatively sure it was a near equal sharing of energy with a nitrogen or oxygen atom. It was probably not nuclear, but a classic hard hit with multiple ionization levels for the gas atom, shearing off a large portion if not all of its electrons. (i.e., 10-50 kev hit and transfer) . This would make the heavy recoil atom almost a naked nitrogen nucleus but without any nuclear event occuring. This might explain the short remnent trails.

Richard Hull

[Jon Rosenstiel]

My error! Of course, nitrogen would be the more likely candidate.

From "The Particles of Modern Physics" by J. D. Stranathan, 1942…

"Many times an abrupt change in direction is accompanied by a spur track. This spur is due to a recoiling nucleus which has been struck by the alpha particle."

What appear to be wires are lines scribed in the condenser plate at 1 cm intervals.

Jon Rosenstiel

[Richard Hull]

Thanks, Jon. I thought the lines might just be lines to assist in energy determination via track length or if a mag field were used, make a crude determination of the radius of curvature for similar measurements.

Richard Hull