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ChrisLX200
United Kingdom
35 Posts |
 Posted - 07/09/2017 : 03:16:08
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There seem to be a lot of SBT-11 tubes offered (on Ebay for e.g.,) described as being SBT-11A tubes. As far as I was aware there are significant differences between the two, the more desirable 'A' version being more sensitive to alpha emitters. Looking at images on ebay, and on YouTube and various other websites, from what I can see the genuine SBT-11A have that exact name printed on the back of the tube. Some of those offered for sale (as SBT-11A) just say SBT-11, or have an 'A' added (probably some time after manufacture?). Some even have an 'A' added hand written on the box :-)
So, how to identify what I want. Must all genuine SBT-11A tubes have that printed on the back - in a kind of dark blue dye? Are all the ones that just have SBT-11 printed on them NOT the 'A' version?
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GMC-300E-plus |
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| Reply #1
Distelzombie
Germany
202 Posts |
Posted - 07/10/2017 : 09:18:46
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I am also interested in this information.
I have to take a look at my sbt-11a. Might take a while,though.
I know it was offered as sbt-11a. |
GMC-300E+ V4.20 with sbt-11a alpha tube
My statements are "stuff-a-hobbyist-says" and not in any way professional. |
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| Reply #2
ChrisLX200
United Kingdom
35 Posts |
Posted - 07/11/2017 : 10:05:53
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| As I understand it the two tubes are mechanically and electrically identical, the functional difference being the thickness of the mica window (it is thinner on the SBT-11A which thus lets through more alpha particles). However that doesn't help to differentiate between the two though as this data is not supplied. It's difficult to get both a large surface area AND very thin (say, 10 micron) mica window, and if you do then the resulting detector is very fragile to environmental changes. Hence, the Mazur 9000 with its 2" dia detector (which is very sensitive indeed) they warn about the potential damaging effects of using it above 10,000ft altitude or taking it on an aircraft. |
GMC-300E-plus |
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| Reply #3
ChrisLX200
United Kingdom
35 Posts |
Posted - 07/12/2017 : 12:03:20
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| Well I have two on order from different suppliers. One is part of an Arduino kit and very definitely indicated as being an SBT-11A, the other is just a tube which is described as SBT-11A but then in the description it says beta/gamma tube (not alpha).. Anyway, the Arduino kit comes with a socket (no soldering directly to the pins) so I can easily swap between the two, I will be able to test both with the Arduino kit detector and also with the GMC-300E+. I have good a/b/g sources to play with but it will take some thought how to compare with some accuracy (also, I don't know what the expected variablity is from tube to tube even when of the same type, so if the difference is not marked I'll be none the wiser :-) ) |
GMC-300E-plus |
Edited by - ChrisLX200 on 07/12/2017 12:04:39 |
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| Reply #4
ullix
Germany
1110 Posts |
Posted - 07/16/2017 : 07:17:19
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I just got SBT-11A tubes. At least this is what it says on the imprint stamped on the back of the tube, see picture. It does look like a genuine print, and not with an "A" added later.
The line below says "9207" and "8806". Is that July 1997 and June 1988, or is that lot 92 from 2007 and lot 88 from 2006? Or something totally different?
I tested the tubes against each other and a M4011 and a SBM-20. The SBT-11A come out very close to a SBM20 and about 30% better than an M4011, when tested on K40 (KCl) and Th (gas mantle). I can't say to what degree -if at all- they respond to alpha emission.
What I did NOT see was the lightshow of flashes in the tubes when reciving radiation that some people found on such tubes.
Is that perhaps the distinguishing feature between an SBT-11 and its "A" version?
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| Reply #5
ChrisLX200
United Kingdom
35 Posts |
Posted - 07/16/2017 : 08:55:11
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I would say both of those are SBT-11A tubes, the images of others I saw had a completely different font for the added 'A' (and not the same colour either). You won't see the flashes except in near-darkness.
With your alpha source (thorium not KCl) close to the tube then inserting a sheet of paper between the two should reduce the count dramatically, that would be a crude confirmation of alpha sensitivity by physically blocking the alpha particles. Because they are so easily stopped you'll only pick them up in the first place with the detector placed within an inch or so of the source which itself is not enclosed (not in a container or plastic bag). |
GMC-300E-plus |
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How to identify SBT-11A from SBT-11?
