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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059
I can test one here, have a few sources to try it with and several working counters thanks to Stella. Can hook it up to a colleagues broadband, they leave the router on all the time so this should be OK.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
radhoo wrote ...
Mads Barnkob wrote ...
Unit #11000003 is now live at: and
I will post pictures of the installation in the upcoming weekend.
Looks great, Mads, and looking forward to your pictures!
Interesting to see that the readings at your location are constantly higher than the calibration data recorded here prior to shipping the unit to you.
@Conundrum: that would be great!
It is located half a meter from my window out on the balcony, on the 2nd floor(top), approximately 8 meters above ground. Other than that, it must just be my location in the world that makes a difference or tube characteristics changed in shipping? :)
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 700
I would assume something is different at your location, unless the height has such a great impact. (I will test this too, soon, also model C will also have an altimeter built in). Normally we all should have mounted our units at 1m above the ground, but this is not always possible for practical reasons.
Talking about variations, in a similar way, the readings in Chicago show smaller values (11000002). Waiting for Tobias to add his unit (11000004), and another one in Germany as I am curios to see what we find there.
Nevertheless these are all small values, hope to never see them on a rising trend ("uptrend"?)
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
radhoo wrote ...
I would assume something is different at your location, unless the height has such a great impact. (I will test this too, soon, also model C will also have an altimeter built in). Normally we all should have mounted our units at 1m above the ground, but this is not always possible for practical reasons.
Talking about variations, in a similar way, the readings in Chicago show smaller values (11000002). Waiting for Tobias to add his unit (11000004), and another one in Germany as I am curios to see what we find there.
Nevertheless these are all small values, hope to never see them on a rising trend ("uptrend"?)
I shall be joining the project soon, and so have a few words to say.
I don't thinking it likely that the characteristics of Mads' GM tube will have changed significantly in transit.
Height above ground is a key factor in environmental monitoring. Airborne particulates descending to earth will only spend a very short time in close proximity to the detector, but will remain on the ground below for very long periods. Where there is a significant distance between the ground and the detector, the radiation coming from particles fallen to the ground will be attenuated by the air, and still more so in rain, mist and fog. This is because the gamma intensity - in our case measured in counts per second - decreases with the square of the distance, which means that if we double the distance to the ground, counts due to the ground will go down four times.
Clearly, this air attenuation is selective for gamma photon energy, with high energy photons being able to penetrate greater distances through the air, and still have enough energy left to knock electrons out of the GM tube wall, which is the main mode of gamma detection in GM tubes.
Registered Member #510
Joined: Sat Feb 10 2007, 09:28AM
Location: Hannover
Posts: 12
The reason is most likely just other geological features or Mads balcony emits a few betas.
In Germany the nation wide ODL (Ortsdosisleistung/local dose rate) network has standardized to a tube heigt of 1.3m off ground and at least 400m² of free space around a node. The problem being, without knowing the isotope footprint at the location you cannot be sure that hard betas will not offset the measured rate. Sometimes there can be a misinterpetation of up to 2-3 times the actual value because using the tubes at the very low end of their range causes nonlinearities that you cannot easily compensate.
The Germans use VacuTec 70031 tubes which have a very high sensitivity, 840counts per minute at 1µSv/h [¹³â·Cs].
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
tobias wrote ...
PM, that behavior goes against the higher readings by Mad's unit.
But radiation from local geology - especially radon geology - and building contruction materials are major contributors to the total background count. The aggregates used in concrete mixes can and sometimes do cause significant differences in radioactivity from concretes that can affect readings in single buildings, groups of buildings, towns, roads or concrete transport structures, and so on. *
Cosmic rays form a significant part of any background count, and counting will not be significantly affected by changes in detector height in the decametre regime. I found that when a very large glass GM tube type G12 was shielded (actually filtered) with 10mm Pb/2mm Al, the diurnal variation due to cosmic rays was easily observed without statistical enhancement, an xy time/counts plot resembling a very 'flattened' sine-wave.
Here are some average backgrounds, country by country:
*Radiological Protection Principles concerning the Natural Radioactivity of Building Materials, European Commission 112, 1999, free pdf here
*NATURAL RADIOACTIVITY IN BUILDING MATERIALS - CZECH EXPERIENCE AND EUROPEAN LEGISLATIONProceedings of the American Association of Radon Scientists and Technologists 2008 International Symposium Las Vegas NV, September 14-17, 2008, free pdf here:
*Radioactivity in Building Materials: a first Overview of the European Scenario Italian National Institute of Occupational Safety and Prevention (ISPESL)Department of Occupational Hygiene, Via Fontana Candida 1, 00040 Monteporzio Catone (Rome), Italy, free pdf here:
Tobias, this one is specially for you: THE RADIOLOGICAL ACCIDENT IN GOIANIA International Atomic Energy Agency, Vienna, 1988, free pdf here:
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 700
Sync wrote ...
In Germany the nation wide ODL (Ortsdosisleistung/local dose rate) network has standardized to a tube heigt of 1.3m off ground and at least 400m² of free space around a node.
I it is very similar here too. For all the units I sent out I recommended mounting them at 1m above the soil, but this is not possible for practical reasons. However the next models will have an altimeter, allowing for some compensation for the radiation absorption in air - if we consider the usual model, also suggested by Stella : airborne radioactive particles falling down to the soil and emitting radiation from that level.
ps: Regarding the hard betas, keep in mind that the units are enclosed in a ~ 1mm thick aluminum case, so what we're seeing is almost entirely gamma radiation.
ps2: #12000008 went online today in Germany
Proud Mary wrote ...
Here are some average backgrounds, country by country:
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
radhoo wrote ...
ps: Regarding the hard betas, keep in mind that the units are enclosed in a ~ 1mm thick aluminum case, so what we're seeing is almost entirely gamma radiation.
...with a small but significant percentage of cosmic ray muons, showing diurnal and semi-diurnal variations including modulation by the 22-year solar cycle.
The state of the solar cycle should be considered when analysing trends in counting rate.
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Global Radiation monitoring system
