Herent, Belgium, March 2015 – data.
I’ve been doing some extra testing on the side to see if I can arrive at a clearer picture of these factors: Does it matter how I hold my Geiger Counter, vertical versus horizontal?
First some general arrival week data:
- March 4, 2015: attic, on table, horizontal: 19630 counts in 8hr12min (492 min. avg.) = 39.9 CPM
- March 5, late: attic, on table, horizontal, window had been open for 2 hours: 18520 counts in 7hr50min (470 min. avg.) = 39.4 CPM
- Overnight, attic, on table, horizontal, window remained closed: 12900 counts in 5hr23min (323 min avg.) = 39.9 CPM
- Friday March 6, 2015 into Saturday, attic, on table, horizontal, window remained closed: 55900 counts in 24hrs0min (1440 min. avg.) = 38.8 CPM
- March 7, 2015, same: 17560 counts in 7hr24min (444 min avg.) = 39.5 CPM
Background radiation range in this Herent attic is clearly still roughly 38-43 CPM (5 CPM range, although this time I only measured 38.8 to 39.9, so only a 1.1 CPM fluctuation range in the above-shown averages over 3-4 days). A late June 2014 24-hour average in the attic was: 41.2 CPM. So, basically, at first impression all appears as normal as can be. Time for some other tests…
Horizontal versus Vertical & Beta blocking versus non-blocking of Beta
I had never heard anyone point the importance of this out to me before. I discovered that this is a very significant factor at high altitude during my last trip USA->Belgium in early March 2015. Turns out, it’s not only the case very high up. Makes sense, of course, as cosmic rays are a major portion of the natural background radiation everyone is being exposed to. (The only place totally devoid of cosmic rays is deep underground in sediment layers (like in some clays!) that do not contain radioactive minerals.
In those above 48 hours nearby official Belgian online radiation monitors showed stable baselines. Attic radiation, measured with the Medcom Inspector Alert Geiger Counter:
- Standing upright (22hr32min average): 36.6 CPM
- Laying down on table horizontally (beta window down, 24hr avg.): 40.9 CPM
Official data at nearby monitors of Lubbeek & Zaventem showed neither data gaps, nor differences between the these two recent 24-hour periods. The graphs plot 5 days of gamma data:
Question now is: is there perhaps a Beta radiation or surface influence factor in the mix of variables playing a role here? I’ve encountered some skepticism by a few individuals on ENEnews about my recent airplane findings. (Regarding my March 6, 2015 blog post, “Geiger Counter Data from Airplane Flights: Denver -> Atlanta -> Amsterdam.“). So, to further check if any other factors than sensor angle could be the cause of this, I did some additional tests.
The area (My home while in Europe, an attic room in Herent, Belgium) had been cleaned and is not particularly dusty at all. The attic window stayed closed during the testing periods.
Next test, I did on top of a ceramic coffee-cup, to lift the Geiger Counter a bit off the table surface. I thought a coffee cup would be merely a radiation blocker (just a bit of mass) and be neutral otherwise. Turned out quickly that this cup isn’t neutral…
- Horizontal with front of meter resting on cup rim (see photo), Beta window upwards: 21940 counts in 8hr33 min (513 min. avg.) = 42.8 CPM
- Horizontal, Beta window down over cup: 20,000 counts in 3hr50min (230 min. avg.) = 86.9 CPM
–> Not only was the first strangely higher than all averages this week, the second was so extremely different that I checked the dose rate near the cup and -lo and behold-, at closest range, it added as much as +0.150 µSv/hr to background. Pretty bad prop for a test, apparently. ;-/ I wonder if it contains a bit of Radium-226 or Potassium-40. I don’t know. Nothing unusual, though, so many things contains encapsulated radiation sources. In any case, it only slowed me down in my quest to get more details about the effect of the pancake angle to horizontal. And (note to self…) it’s a good reminder to check more aspects of a testing environment.
Starting over, this time on top of a comic strip book, and I moved the set-up to the attic axis on the far closed side (backdrop a mostly empty non-radioactive particle-board closet):
- Horizontal, Beta window down on top of book: 1487 counts in 0hr35min (35 min. avg.) = 42.5 CPM
- Horizontal, Beta window down on top of book, but with 1 sheet of aluminum foil over book: 1232 counts in 0hr28min (28 min. avg.) = 44.0 CPM … Please don’t tell me Aluminum foil is radioactive too… [Yes, a little… See link at end.]
- Horizontal, Beta window down on top of book with 5 sheets of aluminum foil over book: 19030 counts in 7hr34min (454 min. avg.) = 41.9 CPM
- Horizontal with front of meter resting on book = Beta window upwards, 5 sheets of aluminum foil over book underneath, and 3 books on top of Beta-window: 21220 counts in 9hr03min (543 min. avg.) = 39.1 CPM (early March 17, 2015)
- Horizontal with front of meter resting on book = Beta window upwards (exposed, no books on top), 5 sheets of aluminum foil on top of bottom book: 22070 counts in 9hrs (540 min. avg.) = 40.9 CPM (double checking the fluctuation range);
- Horizontal, Beta window downward, the 5 sheets of aluminum foil wrapped around the Geiger Counter: 42410 counts in 16hr59min (1019 min. avg.) = 41.6 CPM
- Vertical, the 5 sheets of aluminum foil wrapped completely around the Geiger Counter: 28350 counts in 12hr47min (767 min. avg.) = 37.0 CPM
- Vertical, no aluminum foil or any blocking: 17960 counts in 7hrs58min (478 min. avg.) = 37.6 CPM
- Horizontal, front of meter faces book, no Aluminium foil (removed, back to just 1 comic strip): 13400 counts in 5hr18min (318 min. avg.) = 42.1 CPM
- Vertical, standing (precariously balanced) on book: 41110 counts in 18hr7min (1087 min. avg.) = 37.8 CPM
- Horizontal, simply on the table, nothing else, Beta window downward towards table: 21300 counts in 8hr42min (522 min avg.) = 40.8 CPM
- Horizontal, on book, nothing else, Beta window downward towards book: 18800 counts in 7hr35min (455 min avg.) = 41.3 CPM
- Vertical, standing (precariously balanced) on table (nothing else): 21890 counts in 9hr43min (583 min. avg.) = 37.5 CPM
Overview tables of CPM averages:
Comparing the averages, how much ‘Horizontal’ measurements are clearly larger:
*Horizontal (39.9) versus Vertical (37.2) => + 2.7 CPM difference, or 6.8%, about 7%
**Horizontal (41.8) versus Vertical (37.4) => + 4.4 CPM diff., or 10.5%
***Horizontal (40.9) versus Vertical (37.3) => +3.6 CPM diff., or 8.8 %
Not quite as pronounced as at high altitude, but nevertheless I found a significant difference between horizontal and vertical measurements here at ground level as well.
- The best two measurements for comparing are possibly those where the 5 sheets of aluminum foil were wrapped completely around the Geiger Counter, ’cause whatever radiation came from the foil would be the same for both, and Beta-in-air would be reduced to only the air trapped inside. The difference for that one, Horizontal (41.6 CPM) versus Vertical (37.0 CPM) was -4.6 CPM or 11.0 %.
Attempts at Beta-blocking didn’t reveal anything because, apparently, books and Aluminum foil add at least +2.2 CPM. Apparently:
- Aluminum can contain low-level radioactivity source traces, see “Low-level radioactivity measurements on aluminum, steel and copper“
- Glossy paper, might contain Kaolin, a clay that also contains traces of Thorium and Uranium decay chain radioisotopes, I read in https://www.orau.org/ptp/collection/consumer%20products/magazines.htm
A very significant (solar activity induced) geomagnetic storm happened just after the middle of March. If this had any effect, it did not affect my measurements in the attic near sea-level outside the normal fluctuation range, at least not during those times I was taking measurements.
- Solar storm data: http://www.solarham.net/planetk.htm Screenshot:
- Also, cosmic ray counts in Finland: http://cosmicrays.oulu.fi/ on which you can see that cosmic rays decrease during such a solar storm event (look at the March 17 data):
Conclusions / What I learned:
1) The difference between holding the pancake-sensor Geiger Counter horizontal versus vertical is a significant factor, even at ground-level where I found the horizontal position approximately adding some + 7 to +11 % to the CPMs seen in vertical position.
2) I need to include date and time more precisely, every time, just in case there unusual space weather, to better get to know its possible effects.
3) If I attempt Beta Blocking, I need to test the blocking material better in advance, to avoid “blocking” with a Beta emitter… :-/
!-> In any case, the angle I hold my Geiger Counter needs to be the same if I want comparable data, otherwise the margin of error increases by (at least) another 7%, making comparisons of CPM averages potentially meaningless.
This blog post was an elaboration on my airplane findings shared in (March 6, 2015), “Geiger Counter Data from Airplane Flights: Denver -> Atlanta -> Amsterdam” Hope this is helpful to other independent radiation monitors.
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[Final version. Last updated: March 23, 2015]