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 Incoming gamma radiation 
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Joined: Fri Jul 03, 2015 7:04 pm
Posts: 129
Location: Toronto Canada
The intent of a shielded box is to prove conclusively whether the source is a passing overhead object or Radon decay progeny in the nearby air. I was imagining a lead tube shield at first, then making 2 detectors like yours looking different directions, but I think now the easiest way is to add a shield to the top of your detector, but only half-way (covering say the North half). This way, a N-S nearby pass will show a clear sharp rising peak as it passes overhead, and a S-N pass will show a sharp drop, in the minute-by-minute data. The peaks should show patterns corresponding to the visibility of the satellite (short peaks of a few minutes separated by predictable hours of relative quiet). If this setup still shows a 24 hour pattern however, then the source is most certainly Radon decay progeny in the local air.

I have located a good reference for daily Gamma variations, I'll post this in the Nuclear 101 forum.

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http://netc.com/chart/view.php?n=1%3A77D9CCCA.5 Toronto, Ontario, Canada SBM-20 indoors


Tue Jul 05, 2016 8:47 pm
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Joined: Sat Feb 01, 2014 3:46 pm
Posts: 47
Thanks, Bert, i already added the extra shield almost directly over the GM tube on the North side. Tonight, I will re-program the MPU for a shorter data window, say 30 seconds. if this is still not short enough then we can try 10 seconds, but beyond that, I suspect the counts will be high enough to discern a few chunks but not all, but it is only necessary to see the tapering counts on the south side of center. If this doesn't work out, maybe the 2 inch pancake will be sensitive enough to allow an even shorter count time.
Another test I just made was to use the software calipers on the plot to measure the time between orbit peaks for two chunks at random, where no interfering chunks would cause problems. Easy enough, most of the hot NORAD numbers show 3 passes per day on the plots!
Attachment:
File comment: A small portion of the plot showing triplet passes. NORAD numbers on Y axis, Time on X axis (YY.yyyy)
triplets.png
triplets.png [ 3.18 KiB | Viewed 8754 times ]

The time measured between passes is 10.512 minutes for the two I measured. A 30 second count would be much better for this measurement as well.


Wed Jul 06, 2016 9:40 am
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Joined: Sat Feb 01, 2014 3:46 pm
Posts: 47
That last graphic has the wrong caption...those dots are rise-peak-set timespan, and not passes, they give the time available to collect data. The time between rise and peak is the same as from peak to set for the two NORAD numbers that I checked. Less than 20 minutes per chunk, less the shielded zone. The result of the last two days is here:
attachment=0]debris2.png[/attachment]
Look closely at the grey dots (Bq vs time) and see the linear patterns that now show up with a 30 second count window through the shielded GM tube (the shield now covers the North half of the lead box).The one on the left shows a NS crossing a SN forming an "X" pattern. Most of the NORAD numbers with less than 3 CPM have been removed for clarity, and are most likely to be in the radon zone.
The red dots hopefully eventually will allow an identification of the chunks involved, given enough clean hits. To get a red dot, the time stamp between the peak elevation and the Bq count must match within clock error. There are a few in the high counts that qualify, being well above the noise, and the duplicate pattern in the grey dots is fascinating by itself.
We are getting close.


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debris2.png
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Thu Jul 07, 2016 3:00 pm
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Joined: Sat Feb 01, 2014 3:46 pm
Posts: 47
Attachment:
File comment: Comparison between shielded and un-shielded tube July -06-07
jul07-7.png
jul07-7.png [ 8.83 KiB | Viewed 8559 times ]
Adding the east facing LND714 tube (green) to the above shielded tube data (magenta), The pattern observed in the magenta is visible to a fair degree on the left edge of the first peak of the green unshielded data! The sharp drop-off on the right side of the green peaks has been noticed over several runs and can be attributed to the fact that the tube is in the East facing window-frame of an old barn, and is shielded by massive wooden structure on the West side of the tube. The unshielded tube is failing and needs to be replaced soon as we are losing too much data during its' infamous dropouts. I will be sending it back to LND for analysis (probably quench gas is getting used up?).


Thu Jul 14, 2016 8:06 am
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Joined: Sat Feb 01, 2014 3:46 pm
Posts: 47
I'm starting to think that all counts above .2 Bq are attributable to orbiting debris and the counts below that point are due to local radon. Most of the patterns in the low count zone are random with rare linear diagonals showing through. The SNAPSHOT debris appear to be responsible for only a few patterns, however there is a set of NORAD numbers that have no published orbital elements and might be classified. I suspect that 20048, 38367, 38366, 38371, 38382, 38406, and 38414 are all hot and marked with the letter "C" instead of a "U" in the TLE (Two Line Element) set for the Snapshot debris, and will not show up in any of the Web sites that track satellites. N2YO http://www.n2yo.com/?s=25544 however has all of the unclassified debris numbers in their database and will track them. If these hot numbers are, like their unclassified brethren listed numerically in order of discovery, we should see the activity in between the listed orbits, and indeed, for the most part this does appear to be the case! On the other hand there is a large gap in the number series that is difficult to explain.


Thu Jul 14, 2016 8:16 am
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Joined: Sat Feb 01, 2014 3:46 pm
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Because of the low Earth orbit of the SNAPSHOT satellite, it and all of the debris can be expected to decay, and the orbit calculating software does have drag coefficients that will enable estimates of the loss of altitude and possibly predict re-entry dates. Because of the high level of secrecy involved, there may be no announcement from NASA. I lost the link, but I saw a reference to a project that Japan is proposing to "clean up" the mess of orbiting debris. Could this be something we should watch?


Thu Jul 14, 2016 8:31 am
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Joined: Fri Jul 03, 2015 7:04 pm
Posts: 129
Location: Toronto Canada
Since there are several orbiting debris clouds that appear to be affecting readings, it would be most convincing if the ones we know of are predictably spiking the shielded detector. For example, the SNAPSHOT data for the next 10 days shows the following passes over your location (>70 degrees elevation):
Date time dir
Jul 17 23:17 S-N
Jul 18 23:27 S-N
Jul 19 11:06 N-S
Jul 19 23:37 S-N
Jul 20 11:16 N-S
Jul 21 11:26 N-S
Between now and the 17th, you are in one of the 72 hour blank periods. With more debris than SNAPSHOT's, there will be more spiking between these times as you have seen. But to prove this, it is important that none of the above times fails to show the expected spike: a sharp drop at the S-N times and a sharp rise at the N-S times (assuming the lead cover is on the N side of your detector).

I would love to see another detector like yours. I am finding it very hard to find time to obtain lead shielding during the daytime, (but seem to have plenty of evening time to check websites). Maybe I should reconsider paying shipping costs for lead. :lol:

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http://netc.com/chart/view.php?n=1%3A77D9CCCA.5 Toronto, Ontario, Canada SBM-20 indoors


Thu Jul 14, 2016 8:48 pm
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Joined: Sat Feb 01, 2014 3:46 pm
Posts: 47
My old greenhouse wiring was pulled and is piled up in the back of an old barn... it is sheathed in lead, and should be stripped and melted down for recycling. My father was able to melt lead using a gasoline torch. I wonder if propane is hot enough?

LND quote on single LND714 gamma tubes is $100US each, with a drop to $45US each in lots of 25.
DEMOQE with MPU can be had on EBAY for as little as $45. A small circuit card can be wired up with an SD card socket that I have here. The only other expensive component is the Emco power module at $100+ each. These can be set by potentiometer to any voltage up to 1000VDC, and can operate several types of tubes without software change. The demo board supports use of a scope display via USB so you can watch the data on the screen and make screen shots etc.


Sat Jul 16, 2016 12:54 pm
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Joined: Sat Feb 01, 2014 3:46 pm
Posts: 47
Radioactive Debris in Space Threatens Satellites in Use
By WILLIAM J. BROAD
Published: February 26, 1995 (New York Times)


"After sifting clues for five years, a team of scientific sleuths has found that puzzling clouds of junk orbiting the Earth are made up of radioactive debris leaking from a large group of orbiting Russian nuclear reactors. It is the first major case of nuclear pollution in space and one of the messiest environmental legacies of the cold war.

The atomic debris, estimated at 70,000 detectable particles and perhaps millions of smaller ones, poses no danger to humans, experts say. But it threatens to damage working satellites and will force engineers to add more shielding to help protect new spacecraft."
http://www.nytimes.com/1995/02/26/world/radioactive-debris-in-space-threatens-satellites-in-use.html?pagewanted=all


Fri Jul 29, 2016 8:08 am
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Joined: Fri Jul 03, 2015 7:04 pm
Posts: 129
Location: Toronto Canada
I have finally been able to get lead sheet and make a shielded box to try and isolate the direction that detected radiation is coming. I have to admit that initial results are not too good for proving a satellite source. My 1/16" lead sheet does not appear to stop Gamma radiation at all. With my detector inside a 6 sided box similar in size to Peter's, I get no clear drop in background radiation. The lead fully stops all the radiation from my Uranium glass test beads, but it does not seem to affect background at all. The SBM-20 tube inside is sensitive to Beta and Gamma (not Alpha), so I have to conclude that normal background here is mainly gamma. Certainly any radiation reaching the ground from orbiting debris is also gamma. This observation also casts doubt on the expected sharp drops and rises due to a shielded box top. To see these changes, it would take at least 1" thick lead walls to stop 75% of the gamma from unwanted directions (according to http://www.blackcatsystems.com/GM/articles/alpha_beta_gamma_radiation.html). In addition, concluding that any sharp changes are due to a wooden structure vs. a glass window does not seem right either. The only effective shield in Peter's data seems to be the earth itself (for the satellite component), but this is also a radiation source (for the background component).

Is there anyone with lead bricks at their disposal willing to try this experiment?

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http://netc.com/chart/view.php?n=1%3A77D9CCCA.5 Toronto, Ontario, Canada SBM-20 indoors


Tue Sep 06, 2016 8:45 pm
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