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Americium 241 fluorescence

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Bjørn

Tue Mar 11 2008, 12:50PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

I repeated mine with 100 times more material on the side of the sample to double check that something similar was not happening.

Even if the powder had been in bright light all the time up to the exposure it does not emit any light except where it is excited by the radiation.

The only other light was a reflection on the foil showing light that got around the door. I made an overlay that shows where the light was.

Proud Mary

Tue Mar 11 2008, 02:09PM

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

Very interesting results, both of you. I will set up an experiment at the weekend so I can contribute my own results.

Tesladownunder

Tue Mar 11 2008, 05:51PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Here is a 416 second shot with the phosphors having been covered for some hours. Now more clear red and green discs with only a little phosphorescence. These are 2mm across.

I have a ZnS:Ag sheet that picks up alpha well but will not fluoresce/phosphoresce with my violet laser (yet UV does pass through). The green ZnS I used below above behaves quite differently so may have a different activation. It has bright prolonged phosphorescence under my violet laser.

TDU

1205257877 10 FT40676 Spinthariscope3redgreenfinal

Proud Mary

Tue Mar 11 2008, 08:54PM

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

Here is an interesting paper about strontium aluminate if you blokes haven't already seen it:

The Luminescence from a Long Lasting Phosphor Exposed to
Alpha, Beta, and Gamma Rays Munehiko KOWATARI1, Daisuke KOYAMA2, Yoshiyuki SATOH3, Kouichi IINUMA3 and Shunsuke UCHIDA3. Journal of NUCLEAR SCIENCE and TECHNOLOGY, Vol. 39, No. 12, p. 1251â€“1259 (December 2002)

Bjørn

Thu Mar 13 2008, 08:20AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

I set up my CCD chip and there are two distinct types of detection. One that is weak but very common and a different one that happens a few times a second that often saturates a pixel.

Whatever causes the bright flashes can some time work its way through 6 mm of shield (glass and ferrite). It seems to take a mm or so of shield to halve the intensity. So that makes me suspect it is beta radiation.

The weak detections are quite deep in the noise so it seems like I have to build a PC with a capture card to caputure uncompressed video to study it.

Proud Mary

Sat Mar 15 2008, 05:57PM

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

I used reagent-grade ZnS (>99.8%) and got a null result after an exposure of 300 secs, at f32 on my Nikon D50.

I had hoped that there would be sufficient Ag/Cu impurities in the ZnS to act as dopants, but it seems not.

Bjørn

Sat Mar 15 2008, 06:40PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

f/32?
If so that would be (32/1.4)^2 = 522 times less light gathering power than what I used. Mine would have looked black at f/32.

Proud Mary

Sun Mar 16 2008, 12:37AM

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

BjÃ¸rn BÃ¦verfjord wrote ...

f/32?
If so that would be (32/1.4)^2 = 522 times less light gathering power than what I used. Mine would have looked black at f/32.

Dear me! I must have been half asleep when I wrote that! I meant 3200 ISO speed, [thinking of the fastest speed that I am used to] but now I see I meant 1600 on the D50 in any case! The aperture was f3.5, not nearly so bright as your lens, so perhaps I should give it another go with an even longer exposure.

Bjørn

Fri Jun 06 2008, 09:49PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

The complication is that macro lenses can have significantly reduced brightness when focusing close so without knowing if that happened here we don't know for sure if there is a difference.

I finally got around to test my 150 mm macro lens and it goes from f/2.8 at infinite to about f/5 at closest focus distance. So the difference is dramatic.

I think this is because of the internal focusing design and it would not happen if the lens change size during focusing.

Hon1nbo

Sat Jun 14 2008, 12:41AM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

I just have to say something, even though this thread is old (and b/c I would like some feed back on the matter)... it does not seem that a mirror or leaded glass was used for the initial shot, therefore the ionizing radiation could have directly struck the image sensor... main reason I am posting this is because I did a project a while back in which the radioactive source (U-238, as Am-241 is illegal to remove from smoke detectors now), without any chemicals, produces an image due to the charges generated... I planned to make a geiger counter, but it would be ineffective due to the fact that some of the "counts" lasted for too long: I suspected it was due to the very high charge the ions can create... BUT, after experimenting with Betavoltaics, I wondered if I could use the image sensor off the camera to make a usable voltage... anyone familiar with these sensors?

since the betavoltaics hasn't worked out, I successfully made a psuedo-ionization/electrolysis chanmber that powered the clock off of a thorium lantern mantle... never got enough for the iPod -_0

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