I advise against using smoke detectors. To detect heir alpha radiation, you 
would have to disassemble the source until you get to the radioactive 
isotope plated strip - or button - element. This is sort of not allowed, 
and also can be very dangerous if you scratch off radioactive material. 
>From outside the detector you can only detect the Gammas from the Am-241 
Also Quantities are sort of really high in these devices, depending on make 
and model (1-100 uCi Am-241). If you really want to have alpha radiation, i 
would purchase a Po-210 source from here:
https://www.spectrumtechniques.com/products/sources/disk-sources-and-source-sets/

They are like 60$, safe and legal to handle. Only disadvantage is short 
half life of 138 days. 
You also can find high power Po-210 sources here: 
https://www.imagesco.com/geiger/radioactive-sources.html

Paul Andrews schrieb am Donnerstag, 26. November 2020 um 17:00:06 UTC+1:

> And by 'alpha', I meant 'beta'. I actually did mean alpha, but I was 
> wrong. Still my old Geiger/Muller tube couldn't detect anything from these 
> nixies, so at least I can now detect beta particles. Now I need to find an 
> alpha source! Smoke detectors apparently.
>
> On Thursday, November 26, 2020 at 10:27:17 AM UTC-5 Pramanicin wrote:
>
>> Still a bit of juice left!
>>
>> Sent from my iPhone
>>
>> On Nov 26, 2020, at 07:25, Paul Andrews <[email protected]> wrote:
>>
>> Finally got an alpha detector for my GK-Mini geiger counter. First 
>> picture is a regular nixie tube. Second is one doped with Kr85
>> <IMG_5681.JPG>
>>
>>
>> <IMG_5683.JPG>
>>
>>
>> On Friday, November 6, 2020 at 9:20:54 AM UTC-5 SWISSNIXIE - Jonathan F. 
>> wrote:
>>
>>> Could also be Ra-226 on the 6140
>>>
>>> gregebert schrieb am Mittwoch, 4. November 2020 um 16:32:02 UTC+1:
>>>
>>>> Maybe it's Thorium, used in the filaments.
>>>>
>>>> On Wednesday, November 4, 2020 at 4:13:16 AM UTC-8 Paolo Cravero wrote:
>>>>
>>>>> Hi.
>>>>> Let me add two pictures and a story.
>>>>>
>>>>> Lately I picked up locally a bunch of small CRTs (2BP1, that also fit 
>>>>> in the vintage tuner currently on eBay, plus a Marantz) and the guy had a 
>>>>> few NIB tubes too. I was looking for gas-filled ones and that resulted in 
>>>>> a 
>>>>> W.E. 6167 dekatron, some 0B2WA and some W.E. 6140/423A. Of particular 
>>>>> interest was the 6140 shown in the picture whose box mentions Kr85, but 
>>>>> no 
>>>>> symbol on the glass.
>>>>> When I came home I checked with a Geiger counter and SBM-20 probe 
>>>>> (hard beta and gamma particles) these tubes and the 6140 from 11/61 shows 
>>>>> no action. Same goes for other 6140 except for one, much older from 12/52 
>>>>> marked 423A. Neither the box nor the glass carry any warning sign, but 
>>>>> this 
>>>>> tube hits >600 CPM vs 40 CPM background when put close to the SBM-20 
>>>>> probe 
>>>>> (it's not the right way to measure radiation, but it's cool :) ). There 
>>>>> is 
>>>>> definitely something else than Kr-85 in there! I have blurred pics of it 
>>>>> and it has been stored away from home.
>>>>>
>>>>> As already mentioned, Nixies did contain Kr-85 and I knew I had one 
>>>>> clearly marked. It's a Burroughs Self-Scan display that probably needed 
>>>>> some "doping" to handle the almost 1 MHz scan rate. BTW, it contains gas 
>>>>> and I might never use it, so if someone wants to experiment with 
>>>>> self-scan 
>>>>> contact me off the list.
>>>>>
>>>>> One question for the knowledgeable people in here. I have some Mullard 
>>>>> Nixies marked "Kr-0A": has it got something to do with Kr-85? I can't 
>>>>> check 
>>>>> with the Geiger since my probe does not detect Kr-85 leftovers.
>>>>>
>>>>> So, if you are on the hunt for active tubes, better look for unmarked 
>>>>> pre-1960 editions and carry a Geiger counter with you ;)
>>>>>
>>>>> Paolo
>>>>>
>>>> -- 
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>> .
>> <IMG_5683.JPG>
>> <IMG_5681.JPG>
>>
>>

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