Home Forum Community What the heck are we counting?

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  • #920
    Craig
    Participant

    I re-submitted a question to the Berkeley RadWatch team, with a copy to the RadViews forum –per:

    > http://radviews.com/forums/topic/is-background-monitoring-useful/

    –for which you might care to offer an answer (either here or at RadViews, but our forum here is far more active).

    Craig

    • This topic was modified 6 years, 3 months ago by Radu.
    #925
    Radu
    Keymaster

    I seem to be unable to connect to radviews.com .

    #940
    Craig
    Participant

    I’ve taken the above link twice so far this morning, It works for me and I’m not aware of RadViews having gone down.

    Best I place a copy here –should others in Eastern Europe be having a problem.

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Here’s a question I sent to the RadWatch group at:
    > http://radwatch.berkeley.edu/FAQ

    12/13/2014

    Dear RadWatchers,

    Some while ago I used your utility on the FAQ page to submit a question. Although the “Captcha” indicated that I got the code right and that my question got submitted, there was no automatic email acknowledgement. Perhaps my question didn’t actually get through to you.

    So here it is again via email –or what I remember of it.

    ~~~~~~~~~~~~~~~~~~~~

    * Question: Is monitoring background “gamma” useful?

    (Or: the way I do it, as posted to:

    > http://radviews.com/map/
    –and click through that icon on the Oregon coast to see:
    > http://radviews.com/upload/14183636801565475242.gif )

    * Details (underlying my question):

    ~ Some say that even at sea level (MSL), about half of my count is muons. (Others say that muons hardly register on a standard Geiger counter.) With a high energy capable scintillator, the density runs about 1/cm^2/minute –which pencils out close to MSL background, given the profile of common G-M tubes.

    ~ G-M tube manufacturers’ specifications commonly cite –what I’d call a “noise level”, but what they call “own”, inherent, “self”, or “shielded” background levels that approach or exceed commonly logged MSL background radiation –per:

    > http://www.lndinc.com/products/17/
    (“Maximum background shielded 50mm Pb + 3mm Al (cpm) = 30 )

    > http://www.ebay.com/itm/New-High-Sensitivity-M4011-Geiger-Counter-Tube-/260835055100?hash=item3cbafb15fc&pt=LH_DefaultDomain_0#ht_928wt_862
    (“Own Background: 0,2 Pulses/s” = 12cpm )

    > http://www.gstube.com/data/2398/
    (“Inherent counter background (cps) = 1″ = 60cpm)

    ~ I weighted a sealed, Army type ammunition box with an SBM-20 G-M tube equipped Geiger counter inside and dropped it to a depth of 2 meters off the end of a dock. That cut the normal (40 inches off the ground) background level of 15cpm to about 7cpm (averaged over 20 minutes). That exercise suggests to me that, whatever it is I’m counting:

    > Half or more is coming from the sky.

    > Half or more is not muons, since 2m of water wouldn’t stop them. (Right?)

    ** So I’ll rephrase my question: Does my gamma monitoring (going on for 45 months now) have much to do with the “NORM” plus any on-the-ground radionuclides fallout –that I originally expected to be counting?

    Craig
    Craig Daniels
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Attachments:
    #944
    richardp61
    Participant

    Well my understanding would be that a fair proportion of your BG at sea level will be muons, the exact proportion will depend upon the concentration of NORM, including radon and daughters, in your locality. GM tubes are certainly detecting muons as they are both highly penetrating and highly ionising. I would suspect the counting efficiency for muons in a GM set up would be close to 100%.

    Richard

    #952
    Craig
    Participant

    Thanks for your response/thoughts, Richard, and for your “vote” on this matter.

    I’ve yet to cast my own vote, due to conflicting data and sources.

    I also thought we had to be counting a lot of muons, then Robert Hart (of hardhack.or.au), who deliberately seeks muons (using coincidence counters) told me that Geiger Tubes are less efficient in detecting muons. That even though muons have quite a lot of energy and are heavier than an electron, they tend not to ionize efficiently —but that I should be wary of lead shielding, which might result in muons causing cascades beta, positron and gamma radiation.

    * An industry respected authority and leader of several radiation interest groups plus another guy who runs a Geiger counter company (they get pissed if I use names) have flatly stated that there’s little or no noise, just ionizing events from external sources –like muons –and that without the NORM, cosmic stuff, and secondaries from shielding, a good Geiger counter might read “zero”.

    * However, all G-M tube manufacturers plus two other top guys in the G-M/GC industry have told me that all G-M tubes made since the war have noise.

    ** Again: my 2 meter depth submerged readings were cut in half –suggesting that the radiation was coming from above (since I was out over the water), that since 2 meters of water stopped half of it, it’s not muons, and that even an SBM-20 G-M tube doesn’t have much noise.

    I did that test to verify similar results that a technician for a highly respected private network got (who asked not to be cited).

    Again: all this leaves me with a concern for the meaningfulness of our background monitoring, but without an opinion as to the source/s of our *clicks*.

    * Possibly: what we see of muons (with a Geiger counter) is just showers of secondary stuff, which does get stopped by a few feet of water.

    ** Any more votes from this group?

    #956
    richardp61
    Participant

    Another observation that may be relevant here, and which is the converse of your ‘under water’ experiment Craig, is the way that GM count rates increase with altitude. Many of us have taken GM based detectors on commercial airplanes and have found that the observed rates are around 20x sea level BG. Clearly this is a result of extraterrestrial particle flux (muons and secondary particle showers) so obvious GM tubes are responding to them.

    #961
    Craig
    Participant

    Yes, Richard –plenty of muons up there –where they’re being made, as protons and what-not cosmic particles slam into the upper atmosphere, but also neutrons and consequent transmuted elements/isotopes. Quite a soup –per:

    > https://en.wikipedia.org/wiki/Cosmic_ray

    > http://www.spaceweather.com/archive.php?view=1&day=15&month=12&year=2014
    (and scroll down to “Sky Calculus”)

    But with so many particles and gamma/photonic rays bouncing around an airliner cabin, it’s debatable just what a Geiger counter is responding to.

    > https://www.youtube.com/watch?v=apWRH39Jgcc

    Craig

    #968
    Radu
    Keymaster
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