Amercium 241

[barry wilkins]

I want to have another try to make a radiation detector using a PIN diode,when I tried before but it didnt seem to work.
What I am wondering is how safe is it to cut open the ionization detector in a smoke alarm so I have a suitable radiation source?

Barry Wilkins

[goontron]

Re: Amercium 241

I've done it. No issue the main radiation is alpha with a little beta. Just get a lead can before anything else. I machined my own out of lead blocks and aded a lock to it.

[goontron]

Re: Amercium 241

They are a PITA to get into though. Sorry for the double post. Its just a PITA to edit a post on a smart phone.

[redwire]

Re: Amercium 241

I used to build downhole tools for oil well exploration, with gamma and neutron detectors. The "test" radioactive source was dangerous and so we collected old smoke detectors and put the Am-241 pellets in a metal container with a door.
Am-241 is not so dangerous, you could eat some according to this article: http://www.world-nuclear.org/info/No...and-Americium/
I thought it was smoking cigarettes while handling the stuff and inhaling that is the greater danger.

I don't know why you are using a PIN diode, they are usually for RF high frequency use. Or maybe it's a photodiode?
Smoke detectors use either the ionization principle (radioactive source, ref. MC14468 datasheet)
or the photoelectric (light scattering from an LED/photodiodes, ref. MC145010 datasheet)
There's a few other IC's out there, old datasheets to learn the principles.
If you want to tie into the alarm output of a commercial smoke detector, you can use an opto-coupler on the daisy-chain wire.
Because of the safety aspect and fire-code regulations, I would rather buy a smoke detector.

[stj]

Re: Amercium 241

what's this intended for?
because there is another way.

[barry wilkins]

Re: Amercium 241

Hi thanks for all replies,the PIN diode I am trying to use is a Hamamatsu photo diode that came out of a spectrophotometer its got a range of about 180 to 1000nm .It certainly works in ordinary light so I covered it with Al foil to keep out the daylight.
I have some circuits most of them use a BPW 34 pin diode ,am hoping my PD would be more sensitive than that.
Once I have my piece of Am241 I will try my experiments again (when I can find where I have put the PD !)

Barry Wilkins

[goontron]

Re: Amercium 241

Aly foil will block the majority of the radiation.

[redwire]

Re: Amercium 241

Barry, maybe you have the sensors mismatched?
Am-241 radiation effects photomultiplier tubes and I'm not sure it does much to photodiodes. The photocurrent might not change much to detect radiation.
But I found an app note using a PIN photodiode for gamma detection so I'm full of it.

[barry wilkins]

Re: Amercium 241

Hi thanks for the link to app note .
I am guessing the smoke detector works similar to an electron capture detector used in gas cromatograpthy ,this has two electrodes one of which is a foil of Ni 63 ,the nitrogen carrier gas is ionized by this.
Not going any further into cromatograpthy ,it is a very deep subject ,one of my service managers called it "Black Magic"
Any way once I have removed the Am 241 pellet and found my photo diode ,will continue with my experiments
A BPW 34 is not very expensive on ebay so I might buy one,have not found a PS 100-7-cer-pin for sale ,think they are expensive .
Also I read somewhere any photo electric cell could work ,would be work trying a PV cell out of a garden light
Barry Wilkins

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