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richardp61
ParticipantI realise this discussion is deviating away from security issues so maybe a moderator could move it to a more suitable place in the forum
ParticipantHi Vinz and all
Most of the measurable radiation at the earth’s surface from a GRB will be in the form of showers of secondary particles, principally muons. As muon forming reactions in the upper atmosphere are much less likely for gamma photons below about 10GeV, it is going to be the briefer high energy GRBs that will be detectable on earth.A paper I was reading (Atri, Melot and Karam 2013) just now looking at 2 Milky Way GRBs calculated that they respectively delivered doses of 0.11 and 300uSv, over a period of 0.1sec. I would have thought this puts this class of phenomena within the detectabilty range of our SBM20 based GM detectors. At the top end of that dose range we are probably looking at a muon flux that would saturate the detector so I’m not sure how this would be represented in the read out from any one device.
Participant6hr is probably a sensible cut off which will exclude short-term artefacts but will not miss a gradually rising trend due to spreading contamination etc. Maybe it would be possible to implement a moving average function which could trigger an alarm if an agreed threshold or a given rate of increase is acheived from more than 1 adjacent stations.
There is another kind of phenomenon which I am interested in (not accident related) which could be flagged by an alarm and that is brief but very large positive excursions in count rate at multiple stations caused by CME or even GRBs. It would be neat if we could capture these events as they happen.
ParticipantAnother 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.
ParticipantI think it would be good to have a discussion about this. As I have said to Radu previously, I think it would also be helpful if there was a way for users to flag known anomalous readings due to testing with sources etc so that these are excluded from any alarm algorithm.
ParticipantWell 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
ParticipantDon’t forget there may be civil nuclear reactors and other nuke sites that are not operational power plants e.g. research reactors, decommissioned power plants, fuel reprocessing plants etc
Richard
ParticipantHi to everyone.
My name is Richard and I live in the East Midlands in UK. My day job is almost completely unconnected with physics and nuclear science but I have a number of scientific hobbies of which radiation detection and measurement is one.
I am also handy with soldering iron and have built a number projects including high voltage power supplies for GM tubes and scints, a calibration pulser and various other things. I have assembled and experimented with a number of different GM and gamma scintillation probes.
I have uRadmonitor # 1200000C which is one of Radu’s earlier units – has onboard temp and voltage sensing but no pressure transducer.
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