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Radioactive source

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2010 - » Archive through 01 June, 2011 » Radioactive source « Previous Next »

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mikeb
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Username: mikeb

Post Number: 460
Registered: 02-2008

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Posted on Thursday, 12 May, 2011 - 12:45 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I saw that Max needed a radioactive source this month to test his geiger counter.

There is a radioactive source in an ordinary smoke detector. I think its Americurim (sp?) and is a low level alpha source.

.... just a thought.

rgds

mb
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joe
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Post Number: 1093
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Posted on Thursday, 12 May, 2011 - 12:59 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

It's ok... hes got radioactive balls !!!!!
(Personally I just think he's bragging)

http://www.eetimes.com/electronics-blogs/other/4215354/I-have-radioactive-balls-?Ecosystem=programmable-logic
Read my ramblings - www.techbites.com/joe-farr
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cjaysharp
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Username: cjaysharp

Post Number: 76
Registered: 06-2010

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Posted on Thursday, 12 May, 2011 - 09:51 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Gas lamp mantle might still work, I think it's thorium BICBW
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alec_t
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Post Number: 635
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Posted on Thursday, 12 May, 2011 - 10:23 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

IIRC the luminous paint on watch hands used to be a feeble source. Is that still the case?

Alec
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cjaysharp
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Post Number: 77
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Posted on Thursday, 12 May, 2011 - 10:52 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hehe, not always a *weak* source, ISTR it was radium, i was told a story a long time ago (possibly by my physics teacher) of someone demonstrating a geiger counter, a visitor offered up his watch and the hands were giving a higher count than any of the lab sources the demonstrator had by a large margin.

The Radioactive Boy Scout is a very interesting read.
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zeitghost
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Post Number: 1632
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Posted on Friday, 13 May, 2011 - 09:53 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I think they took the thorium out of gas mantles.

I have one that gives a nice tick, the newer one doesn't.
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arw
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Username: arw

Post Number: 1023
Registered: 04-2005

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Posted on Friday, 13 May, 2011 - 11:46 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Just nipped into my haunted garage, yes I have some spare Coleman mantles that are non-radioactive. Found these interesting clips on Youtube...

http://youtu.be/095uCbLssKY

http://youtu.be/mv45jVJEkqs (Russian?)

- Alan
Alan Winstanley -- EPE Magazine Online Editor
Subscribe now at www.epemag.com!

www.EPEmag.net - hobby electronics and more
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cjaysharp
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Post Number: 78
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Posted on Friday, 13 May, 2011 - 06:14 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Is your counter sensitive to Alpha particles though? Depends on the window material IIRC..

Probably for the best that there's no thorium any more I suppose, I don't fancy the idea of a powdery alpha source being inhaled if/when the mantle is broken.
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mikeb
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Post Number: 466
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Posted on Saturday, 14 May, 2011 - 11:05 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Why does the mantel contain thorium? Does it somehow convert heat to photons?
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terrym
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Posted on Sunday, 15 May, 2011 - 02:19 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Basically, yes.
This link gives more info:-

http://en.wikipedia.org/wiki/Gas_mantle

TM
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zeitghost
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Post Number: 1633
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Posted on Monday, 16 May, 2011 - 04:08 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

My counter has a metal tube with no window & that still counts, so it must be detecting gammas.
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conundrum
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Username: conundrum

Post Number: 30
Registered: 06-2006

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Posted on Sunday, 29 May, 2011 - 12:30 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi, has Max tried measuring the output voltage using a high impedance voltmeter?

If you don't have one a simple workaround is to put 9 10M resistors in series and connect to a standard cheap DMM, this will give you a 10:1 stepdown if the DMM has 10M input resistance.
This yields 37V at the 370V working voltage of the GM tube if all is well.

It should be about 370V or there abouts, if it is closer to 150 then it is likely to be a bad transistor or backwards Zener in the regulator.
Typically they use an MPSA42 as it takes >300V Vceo without breaking down.

My counter developed a bad tube which would randomly break down and cause bursts of activity separated by periods of nothing at all, not unlike a faulty fluorescent tube.
Cleaning didnt help, I had to replace the bad tube which cost about £10 from the Ukraine.

I also obtained some nice "midget" tubes which are small enough to fit inside a mobile 'phone :-)
SBM21 IIRC.

Hope this helps, -Andre

(Message edited by Conundrum on 29 May, 2011)
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vlf
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Post Number: 241
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Posted on Monday, 30 May, 2011 - 03:51 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

This might be a little cheeky but; within the same area of discussion...
a certain "E"uropean Magazine June issue, has an article for a
Radiation Detector; using a Pin-Photo-Diode # BPW34 instead of
a Geiger-Müller Tube.

It's an interesting idea and costs around .576 pence each, via RS...
the BPW34 cost, depends on the supplier you use.

I found RS the lowest for minimum of five, and the article states that
they can be paralleled, so to get an area sensitivity compared to a
standard Geiger tube.

You can purchase just the article on there web-site, by buying points;
this is just 10 for £1-10... you need to be registered to access this.

For info on Pin-Photo Diode interaction, see pdf down-load... URL:

www.physics.montana.edu/students/thiel/docs/Detector.pdf

Regards, Brian L.
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mikeb
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Post Number: 467
Registered: 02-2008

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Posted on Monday, 30 May, 2011 - 04:49 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

@vlf

Thanks for your post - I was thinking along the same lines. I wanted to detect the motion of an object in a tube. I wanted a very low power solution (solar powered). I thought a 'radio active beam break' would at least eliminate the transmitter power needs.

Hmmm ... I think my old smoke detector will be dismantled this weekend.

rgds

mb
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istedman
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Post Number: 211
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Posted on Monday, 30 May, 2011 - 11:23 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

If you want a low level gamma radiation source, an old CRT TV will do. Just point your detector at the screen and you should register something with the set operating.

Ian

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