| T O P I C R E V I E W |
| ullix |
Posted - 08/20/2018 : 06:47:40
Correction: see Reply #5: this is not the SBM-21 tube, but the SBM-10!
In the wake of discussions on the SI3BG tube, the 2nd tube in the 500+ counters, I ordered some SBM-21 tubes.
Tiny is not exaggerated, they are thinner than a pencil just an inch long. The picture shows some tubes in comparison.
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The cathode end fits nicely into the holder clip of the counter, and the anode is connected in the SI3BG side with a bit of jury rigging. May look wild, but you can even close the counter and measure. Here an example using gas mantels, one on each tube.
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The count ratios are 3060:640= 4.8 for the Th mix of beta and gamma. Poisson looks fine.
For a more detailed comparison I took to the RadMon+, as it is easier to measure in a Potassium sandwich since the tube is not in a case: Put a pound of K-salt (KCl (recommended), K2CO3) in a plastic bag on a surface, put the tube on top, and cover with another pound K-salt in a plastic bag. Makes for intimate contact and high count rate, and is much better to reproduce as the salt is all around the tube and geometry does not play a significant role.
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The 4 SBM-21 tubes are basically all the same, and so are the 2 M4011 tubes (within statistical uncertainty). The SBM-20 comes out highest (~50% higher than M4011). The SBM-21 is 4.5 times lower than the M4011, similar to before.
The SI3BG barely gives some counts, averaging at CPM=0.67, some 420 fold lower than the M4011!
Remember this is for the K-40 radiation of hard gammas and rather hard betas, in a ratio o 9:1 beta:gamma.
While the sensitivity of the SBM-21 is ~5 times smaller than the M4011, whether you take its active length or its volume, both are at least 5x smaller than the M4011, its performance is surprisingly high.
I don't know what its pure gamma response is, but it could have been a much nicer tube in the 500+ than the SI3BG.
You could have put 5 of them in the counter and got the same sensitivity as with the M4011, yet could have switched off tubes for higher count rates.
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| 19 L A T E S T R E P L I E S (Newest First) |
| ikerrg |
Posted - 11/09/2018 : 01:46:18
All that makes some sense even when it looks very odd. The cancerous cells are known to be less resistant to radiation than the healthy cells, because the mechanisms to repair the DNA do not work so well in cancerous cells. So it could be that a mild external and homogeneous radiation during a long time can kill the incipient tumours that the immune system is supposed to stop, but for whatever reason it does not. Cancer seems to consistently start after a drop in the immune system efficiency, and that happens many times after highly upsetting events in a person's life. If the mild radiation controls the growth of these cancerous cells in the initial stages, and give some time to the immune system to recover and attack them before they protect themselves, it could save you from developing a tumour. Who knows! |
| ullix |
Posted - 11/09/2018 : 01:14:28
Perhaps with the slogan:
"Relaxing Radiation - leave the workout to your Geiger counter"
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| Stargazer 40 |
Posted - 11/07/2018 : 04:42:47
I don't know ikerrg, given the discussion of Radiation Hormesis in the 'Cat Scan results' thread, Chernobyl might be destined to become a very popular resort town. :-) |
| ikerrg |
Posted - 11/07/2018 : 03:32:09
Mine is SBM-10, as I said in replies #6 and #7. It is 25mm long and it is more sensitive than SBM-21, and the sensitivity uncertainty is smaller as shown in the specs. Yes, I did not realised that you were saying that the SBM-10 was 21mm long (in your reply #12).
I don't think I will use the tour card, going to Chernobyl is not in my ToDo list ;)
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| Stargazer 40 |
Posted - 11/06/2018 : 15:48:46
Ooops, you guys didn't catch it, but 21mm long is the SBM-21. I did get the right GM tubes. Not even Russian translation error as the 21 is arabic numeral. Doh! Still I did get the tour card to Chernobyl. |
| Stargazer 40 |
Posted - 11/06/2018 : 15:46:09
Yes I got the tour card. I wonder what the Take With You list looks like as to clothing, dosimeter, etc? Is lunch provided?
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| ikerrg |
Posted - 11/06/2018 : 10:43:43
Probably the same as mine also! Did you get a card with a discount for a "Chernobyl zone tour"?
I do not know if these tubes are still from the cold war era or they are newly produced devices. |
| Stargazer 40 |
Posted - 11/06/2018 : 08:24:32
I also got SBM-10. 21mm long. Must be same Ebay seller as ullix in Ukraine. |
| Stargazer 40 |
Posted - 11/05/2018 : 08:32:16
My pair of SBM-21 GM tubes is in the US Postal System. Looks like they will actually make the Nov 8 projection of delivery. Looking forward to seeing if they are 21s or 10s. At least easy to figure out with ruler. Now I need to find a 3 pin DIN to allow another DIY wand type to be added to the 500+V1. |
| Stargazer 40 |
Posted - 11/05/2018 : 08:30:03
My pair of SBM-21 GM tubes is in the US Postal System. Looks like they will actually make the Nov 8 projection of delivery. Looking forward to seeing if they are 21s or 10s. At least easy to figure out with ruler. Now I need to find a 3 pin DIN to allow another DIY wand type to be added to the 500+V1. |
| ikerrg |
Posted - 10/16/2018 : 00:42:42
It took about 2.5 weeks to arrive to the UK. It is a good tube with an intermediate sensitivity (basically a short version of the well known SBM-20). As ullix said, having 4 or 5 of those and turning them on and off depending on the radiation level (or user setting) would make a great counter. Just as an idea for GQ and a future GMC-550+!
Now that I have the 500+V2 I should retake the idea of the hardware switch for the 500+V1. And I plan to do something more "plug and play" for the SBM-10 tube, which combined with the switch in series with the M4011 (or no M4011 installed at all) would be ideal for an intermediate sensitivity counter, not for background but much better than M4011 for intermediate/high fields (like your Cs137 source!).
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| Stargazer 40 |
Posted - 10/15/2018 : 12:40:47
Just ordered two of these to test with the V1. Looks like a month to get them from Ukraine. |
| ikerrg |
Posted - 09/13/2018 : 01:47:29
Just to show you that I received the SBM-10 and temporarily connected it. It is measuring correctly, and it is much more sensitive than the original SI-3BG. I haven’t done proper long measurements, because first I want to define a mechanical system to easily connect the tube when I want to replace the SI-3BG for a specific measurement. I do not want to totally discard the SI-3BG, it has its purpose, especially when I receive the rest of the items to place a switch in the M4011 tube.
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| ikerrg |
Posted - 08/21/2018 : 10:07:34
I ordered the SBM-10 because it is a bit more sensitive and the sensitivity uncertainty is smaller than in the SBM-21:
h**p://www.gstube.com/data/2399/
h**p://www.gstube.com/data/2396/
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| ullix |
Posted - 08/21/2018 : 04:01:31
I think I was cheated with tube order: I did not get the SBM-21, but the SBM-10: 25.5mm instead of 21mm. Ebay shipment from Ukraine.
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| ullix |
Posted - 08/21/2018 : 02:00:45
to complement the data here an overnight background for the M4011BLK and the tiny SBM-21.
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The SBM-21 has a relatively lower background than the M4011BLK, ratio is 5.92 while the Th counts had a ratio of 4.8. So a better signal to noise ratio; more sensitivity for a given background.
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| ullix |
Posted - 08/21/2018 : 01:43:15
@the_Mike: the case can be closed as it is, but I think there is too much jury-rigging for this to be a transportable device, like for carrying into an airplane. Though I can shake it hard and it does not fall out. |
| the_mike |
Posted - 08/20/2018 : 16:15:01
Interesting little tube, the SBM-21... Have you tested it with a closed case, too?
If GQe is ammending the calibration in the firmware, it might be a good idea to start a "calibration table" with recommended cal-points for different tubes, as we all seem to have other preferences (ullix with the SBM-21 and SBM20, jkerrg with the SBM-10, I with a SBT-9, sure others could provide different tubes, too) |
| ikerrg |
Posted - 08/20/2018 : 07:23:58
So you got ahead of me! I haven't even received the SBM-10 yet (SBM-10 is very similar to the SMB-21). Thanks for giving me some ideas for when I get my SBM-10, and thanks for confirming what I wanted to do by swapping the SI-3BG for the SBM-10, which I think is a much better companion to the M4011 (if the HV circuit was able to feed them anyway). I love your solution to mechanically and electrically fix the SBM-21 to the connectors.
For me it is now clear that the SI-3BG is a good tube for extremely high intensity & high energy EM radiation, and not for particles. It is not a good tube for a consumer device. However, having a M4011 with a SBM-10 will require a better HV circuit and a better firmware algorithm to combine both readings. Do you know if the RadMon+ firmware is easily customizable without being an expert in low level assembly coding or something like that?
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