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Bjørn

Sat Feb 27 2016, 05:25PM

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

Dragon64 wrote ...

BjÃ¸rn wrote ...

Americium-241 decay into neptunium-237 and so on fast enough that samples from used smoke detectors can have have 10-20% non americium content. All my samples emit beta in addition to alpha and gamma.

Assuming these sources mostly americium to begin with and that they are no older than 20 years, wouldn't it be closer to ~3%? non americium content? (I don't know the time it takes for americium to go from being coated on those small discs to when they go out for sale)

Yes, looks like I added a zero. What I am getting at is that depending on the detector the radiation detected my not be from americium at all since a pure sample is not pure for long.

Proud Mary

Sat Feb 27 2016, 08:41PM

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

Am-241 data sheet attached as pdf
]am-241.pdf[/file]

Conundrum

Mon Feb 29 2016, 05:23AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Thanks!
Also there is a bit of controversy concerning one of my ideas, seems someone may possibly have found it on Hackaday after all but they either couldn't get it to work (see later threads) or as someone mentioned they might have discovered a related effect independently.

However its nice to see one of my observations proven feasible at last, this at least proves that I might have been on the right track all those years ago.

(edit:)

Wolfram

Tue Mar 01 2016, 07:40AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Conundrum wrote ...

Thanks!
Also there is a bit of controversy concerning one of my ideas, seems someone may possibly have found it on Hackaday then found that claiming as their own work was easier than trying to reference a forum.
However its nice to see one of my theories proven at last, despite overwhelming odds.

What is your theory and do you have a link to where you posted it?

The thesis you talk about never mentions pyrolytic graphite nor radiation windows.

Accusing a master thesis of plagiarizing your work is a pretty serious accusation.

Conundrum

Tue Mar 01 2016, 04:22PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Essentially the main difference between the two is the thickness.
I found that even a relatively thick (<0.2mm) pyrolytic graphite sheet worked, way back in 2009-10 one very cold January.
As pyrolytic graphite is covalently bonded graphene and in fact one can be made from the other as Andre Geim discovered recently the properties are similar.

See posts on 4HV here

also

,d.d2s
Also worth mentioning, comparing the two basically identical cameras (acquired a second one just to do this test) revealed that the PG window was at least double the alpha transparency of the mica+silver and two different amplitudes of signal were being seen on the 'scope trace as expected for 241Am.

I'm not sure why it worked well with one sample and not as well with others, still have to try the same experiment with a bigger sensor and samples from a more consistent source.
Its possible that the difference is the proportion of covalent bonding, how would I check this?

Proud Mary

Tue Mar 01 2016, 10:01PM

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

AndrÃ©, I thought you my find this paper interesting: Using CMOS Sensors in a Cellphone for Gamma Detection

Conundrum

Wed Mar 02 2016, 06:06AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Thanks!
I also did use my phone for a while when trying to get pictures of X-ray film and noticed on the playback quite a few dots resembling something like a colored snowstorm.
Maybe 2-5 per second but see my Youtube video conundrum2009

Whats really sad is that back in 2012 I was trying to get a paper together but a certain magazine which shall remain nameless wouldn't even consider it for publication because it was "too esoteric".
this could have provided concrete proof that I discovered the effect years before, never mind.

Maybe I can self publish? now the technology has moved on a bit single chip photomultipliers are available.

Uspring

Wed Mar 02 2016, 11:11AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

Its possible that the difference is the proportion of covalent bonding, how would I check this?

Stopping power (dE/dx) for alphas is pretty much proportional to electron density and that is more or less proportional to mass density. My guess is, that you look for materials, that are opaque for light for small thicknesses.

Wolfram

Thu Mar 03 2016, 09:40AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

Conundrum wrote ...

also

What is your "theory"? I read through all of the pages you linked and the links back to 4hv from hackaday. You never actually give a clear theory or even a hypothesis. The common theme seems to be that pyrolytic graphite can be used as an alpha window. This is not a new discovery, this is basic radiation physics, and we have equations and models to calculate the attenuation for a given thickness of a given material.

If pyrolytic graphite attenuates alphas to a smaller degree than the formulas and models predict, then it's an actual discovery. This should be pretty easy to measure with a mica window geiger tube and a smoke detector source, by for example comparing the attenuation of pyrolytic graphite and regular graphite of the same density (g/cm^2). If there turns out to be a major difference then you can do a more thorough experiment to exclude possible sources of error.

Again, the thesis you linked uses graphene as an ion detector, which is something completely different.

By the way, be careful with the use of the word theory in the context of science. A theory includes a hypothesis to explain an observation, and evidence to excude other hypotheses. What you have can be called an observation.

Conundrum

Thu Mar 03 2016, 05:01PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Will do.
I actually did notice that here

is a sensor with very similar characteristics.
Its actually based on a CsI scintillator and a low cross section window likely Al or Be.

Also relevant, on later analysis it suggests a factor I had not considered namely the degree of covalent bonding between the graphene sheets.
As this is quite difficult to measure it could explain some of the differences between my results and others; as PM has mentioned there is also the factor of damage to the CCD/CMOS chip(s).

I propose a simple experiment to test this: namely obtain 10mm2 samples of pyrolytic graphite and regular graphite such as a piece of purchased motor brush then sand them down to precisely the same thickness as mentioned in my original post using a micrometer to check each sample.
Then apply silver using a mask to the centre of side 1 and a corner each on side 2, and perform a measurement of resistance, this then allows me to measure this currently unknown factor.
As the silver should not affect anything else apart from causing a drop in sensitivity "head on", this should then simplify future tests.

This also suggests another more interesting possibility, apply DC or AC current to see what that does to the transparency effect.

This does also prove a valid point, doing research on a shoestring is unwise if you don't have the proper facilities.
A scope last calibrated in 1992 and a camera originally designed for car reversing isn't the best starting point.

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