January 24 Through February 4—TUCSON, ARIZONA: Annual show
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Tue Mar 19, 2024 4:35 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Some cool DIY project: spinthariscope
PostPosted: Thu May 13, 2010 5:14 pm 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1284
To detect radiations from radioactive minerals (containing uranium and/or thorium), Geiger counter are usually used, but these are expensive tools.
However a spinthariscope will do just fine, and it can easily be constructed from cheap material.

Note: a spinthariscope will react to radioactivity (alpha particles) from a mineral. That doesn't mean it would detect an irradiated stone (as irradiated stones are not supposed to be radioactive after the treatment)

How it works: when an alpha particle hit the a luminescent screen, one will observe a small flash on the screen.

What you need to build it:
a tube, the inside of the tube must be matt black (you may use a PVC or copper plumbing pipe and paint it black on the inside)
a magnifying lens (you may use a 10X triplet loupe lens)
a luminescent screen (usually a sliver activated zinc sulfide coated sheet is used).
Note that ZnS(Ag) scintillation screens for spinthariscopes can be bought from ebay (about 10$). It is possible to build it yourself instead of buying it.
some glue for the assembly (use solvent-free glue so not to fog the lens with glue vapors)

How to build it:
Fix the magnifying lens on one side of the tube.
On the other side place the luminescent screen, with the sensitive side of the screen (the powder coated one) facing the outside.
The tube must be the right length so that the lens is correctly focused on the screen (or make a focusable device by using two tubes, one sliding into the other), as you want a clear image.

How to use it:
Place your eye against the magnifying lens, and watch the mineral through the device. The mineral must be very close to the device, meaning 1cm from the luminescent screen or less.
Just be careful not to scratch the screen with the mineral, to avoid that you might add a metallic grid (painted black) in front of the screen so to protect it.
You need to be in complete darkness, and stay 10-15minutes there until your eyes will adapt to the dark. Otherwise you won't see anything.


Spinthariscope drawbacks:
-can only be used in complete darkness
-non immediate observation (as you need time to adapt you eyes to the dark first)
-can't be used for prospecting uranium ores in the field (you need a geiger counter to do that)
-can't be used for sorting quickly a large batch of minerals.

Spinthariscope advantages:
-it has a very good sensitivity (one can clearly see the impact of a single particle on the screen)
-it's very cheap and easily made yourself
-it's only sensitive to alpha rays, which means that only the mineral radioactivity is seen, with no interferences from environmental natural radioactivity. That means that if you see something, then you can be sure that the specimen is radioactive, without a doubt.


Now, if you've not yet understood why spinthariscopes are so cool, just check this:

http://www.youtube.com/watch?v=2iwRbIMpPMs

:D


Last edited by cascaillou on Tue Apr 22, 2014 7:33 am, edited 12 times in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat May 15, 2010 12:23 pm 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1284
So here's a diagram of the spinthariscope I'm currently making (the diagram is not to scale, and the many colors are only there to make it easily understandable):

Image

Note that in this design, there is no moving parts. So it must be built so the lens is already perfectly focused on the screen (which means that if your lens has a focal length that is different from mine, then you might have to use longer or shorter copper tubes to get it correctly focused on the screen).

One fist have to get his hands on some magnifying lens, and THEN find a copper tube that will fit it just fine and then find another copper tube that will fit the first tube (so you have a lens that slide inside a first tube, which itself slide inside another tube).
Glue that is used for assembly must be solvent-free glue (which gives off no vapours)

As you can see there's no protective grid but there's a removable plastic cap instead. That is because I build a small diameter device (which means small luminescent surface) and I thought that a grid would reduce even more the available screen contact surface (for the alpha particles to hit).
However, that means that once the protective cap is removed, one will have to be careful that the observed rock specimen doesn't make direct contact with the screen (as you don't want to rip it). If the cap is made of translucent plastic, apply black paint on the outside of the cap so to make it opaque.

Will post a picture of the device when it's finished and tested.


Last edited by cascaillou on Sat Oct 01, 2011 2:05 pm, edited 15 times in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sat May 15, 2010 4:42 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2659
Very nice! :D


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun May 16, 2010 9:41 am 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1284
ok, I just finished the thing just as described in the diagram.

Will go and buy some radioactive mineral sample tomorrow so to test the device (the luminescent screen I used is a bit old and has lost some of its powder but I think it should work)

Some advice: You need a paint that works for metal. Before applying the black paint, use sand paper on the inside of the copper tubes (paint will stick better on sanded surface). Then, for applying paint, use a good paint brush which hairs are soft and flexible (don't use a stiff one). You want the paint layer as thin as possible. Wait a few days until the paint is completely dry before assembly!

By the way, I didn't need any glue for assembly, as the black paint layer had narrowed the tubes diameter a bit, so I just had to force things one into another and then it wouldn't move anymore.


Last edited by cascaillou on Mon May 17, 2010 5:21 am, edited 1 time in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun May 16, 2010 5:28 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2659
How are you making or where are you getting the scintillating screens?

Did you notice that when you click on the link to the spinthariscope video ther e are some cloud chamber videos.

If you are interested enough in radioactive goodies to build a spinthariscope then you need to build a cloud chamber too. There are tons of plans out there on the net.

I have not built one yet but if I live long enough I definitely will.
A bubble chamber would be even neater but that starts loosing touch with reality. Not that that is really a problem. :roll:


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun May 16, 2010 6:53 pm 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1284
Quote:
A bubble chamber would be even neater but that starts loosing touch with reality

hahaha creazy idea I like it

Quote:
How are you making or where are you getting the scintillating screens


The screens can be bought from ebay (cheap stuff), just search for 'spinthariscope' and you'll find these, here's the link:
http://cgi.ebay.com/ZnS-Ag-scintillatio ... 519093fa4e
This is a reputable ebay source for such screens, I bought mine from him.

For cutting the screen at the desired shape and dimensions, use clean scissors, holding it carefully by its edges so your fingers won't be removing too much powder from the screen. Also make sure that your hands are clean and dry before proceeding.

Otherwise you can make a scintillation screen yourself:

You need colorless transparent scotch tape (which can be cut at the desired shape and dimensions).
And you need a luminescent powder: preferably Ag activated ZnS powder (it's rather safe and works just fine), but some other chemical powders can be used instead, see detailed discussion here:
http://old.4hv.org/index.php?board=4;ac ... eadid=1369
Some powders are less suitable than others due to poor luminescence, or because they also exhibit some phosphorescence (causing a blurry sight). You have to find the right kind. You can use luminescent powder (pixel phosphors) from inside a CRT television/computer screen, it is said to work fine but also toxic.
Then all you need to do is sprinkle the powder on the adhesive side of the scotch tape so that a very thin layer of powder will stick on it. Avoid making lumps, shake off excess of powder that hasn't been stuck by the tape. The resulting screen will be whitish and somewhat translucent. That's it.
(proceed on a clean surface, with clean dry hands, so to avoid any dust/dirt sticking on the tape or moisture going into the powder)

Keep luminescent powders/scintillation screens inside a ziplock plastic bag until use (away from dust, heat, light and moisture), avoid rubbing the screens.


Last edited by cascaillou on Mon May 17, 2010 8:45 am, edited 7 times in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun May 16, 2010 11:25 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2659
I actually know the guy selling the scintillators. He lives near St. Louis and we have met in the local electronics surplus place which I started going to at the age of eight.

He is a radiation physics hobbyist and has outbid me on some cool things on ebay.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon May 17, 2010 12:25 am 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1499
G4Lab wrote:
If you are interested enough in radioactive goodies to build a spinthariscope then you need to build a cloud chamber too.


I really like this little cloud chamber. It works great, and it doesn't need dry ice or LN2. It is a fun little demonstration.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon May 17, 2010 5:58 am 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1284
Here's a pic of my pocket sized spinthariscope (next to its protective cap):

Image
so you can see the screen side of the device

the cap was made from a tiny plastic shampoo bottle (I did just cut the base of the bottle and used it as a cap). It must have the right diameter so to fit the device, however if it's a little too wide, just stick a thin piece of rolled cardboard inside of the cap so to reduce its diameter a bit and that will do just fine.


Last edited by cascaillou on Tue Apr 22, 2014 7:45 am, edited 2 times in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon May 17, 2010 10:44 am 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1499
It looks very cool... like a piece of optics from the first half of last century. Have you tried it out? What source of alpha particles are you using?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon May 17, 2010 2:10 pm 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1284
Not yet. I will go and buy some small sample of autunite or torbernite tomorrow. I can't wait, high energy particles crashing right into my eye at 15millions meters per seconds sound so damn cool hahaha :lol:

ps: more seriously, it's not big concern, alpha particles are stopped by a simple paper sheet or a few centimeters of air, and despite beta and gamma rays are not, the duration of exposure will be very short anyway.
But always thoroughly wash your hands after manipulating any kind of radioactive material.


Last edited by cascaillou on Tue May 18, 2010 8:50 pm, edited 2 times in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue May 18, 2010 1:39 pm 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1284
So, I just tested the device (with radioactive mineral betafite) and it works fine.
However, one really need at least 10 boring minutes of dark adaptation before starting to see anything clearly.


Last edited by cascaillou on Tue May 18, 2010 2:44 pm, edited 1 time in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue May 18, 2010 2:18 pm 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1499
Cool choice for a mineral to testing. How many counts per minute were you able to see?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue May 18, 2010 2:44 pm 
Offline
Gold Member

Joined: Sun Jun 28, 2009 9:56 am
Posts: 1284
well, I just checked that it was working, but I didn't try to count the tiny flashes (maybe 10 within 5 seconds?).
I must say that spinthariscope isn't that much ease of use, at least for my eyes (very small fleeting flashes, difficult for the eye to focus in the dark, phosphenes in my vision)


Last edited by cascaillou on Sun May 23, 2010 4:42 pm, edited 2 times in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue May 18, 2010 3:58 pm 
Offline
Platinum Member
User avatar

Joined: Tue Jan 02, 2007 8:20 pm
Posts: 2659
Which is why God invented the photomultipier tube, intensified vidicons, and photon counting gear. :D
A scintillation counter is a spinthariscope hooked to a pmt and cointer.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock