Does background radiation have a diurnal variation?

[CWatters]

On another forum someone has been reporting on their efforts to characterise the background radiation in their lab prior to running some experiments. They don't have much data but what they have appears to have a daily cycle. They weren't looking for one and they haven't done enough work to eliminate all possible causes, but just for interest I went looking for other reports and found someone with many years of data and what looks to me like a very similar pattern.

See graph "Radiation by local solar time"" about way down this page..

http://www.fourmilab.ch/documents/cosmic/

Is this something that's understood?

 

[Vanadium 50]

Given that many detectors and readouts have a temperature dependence, I would want to control those before jumping to any conclusion.

 

[mfb]

The linked website doesn’t discuss temperature at the measurement site at all. That doesn’t pass even a very rudimentary quality check.

 

[CWatters]

Understood.

Late last night i found a paper here...

https://www.google.co.uk/url?sa=t&s...Vaw2f7KpRvFpKDF4_0uZ-XlQ-&cshid=1542333222747

Which claims temperature and humidity cause a daily cycle in both alpha and gamma radiation and references other papers. The cycle appears very similar, higher AM and lower PM with quite a rapid change just before mid day.

They suggest temperature effects the rate at which radon is released. I don't see where they check for the effect of temperature on sensitivity either but perhaps I missed it. Need to read it again.

 

[CWatters]

Darn it. Anyone know how to make links found by Google work?

That paper is titled "Diurnal variation of radon progeny".

 

[256bits]

http://nuclear.ee.duth.gr/upload/2007 JENVR 2007 Rn 1.pdf

 

[gleem]

This is another example of why "citizen scientists" should not post results of their "investigations" without a review from a qualified expert. It is also another reason to keep scientific instruments out of the hands of amateurs. GM counters are simple to use but problematic when interpreting the results.

His concern and musings over the asymmetry in the count rate distribution are a wasted effort. The distribution is not exactly Gaussian but Poisson which still manifests a slight asymmetry at his count rate. His two distribution hypothesis is fallacious and should not be used for this experiment.

The detector is sensitive to all types of ionizing radiation which in this case have different sources whose radiation comes from different directions. The efficiency is directionally dependent.

The data were accumulated over the complete seasonal cycle. He is at a high elevation so during the winter the house is closed tightly sequestering the air and probably allowing radon to build up to higher levels than in the summer. He merges all the data without any concern for the possibility of seasonal variations.

And finally he states results in uR/hr (a unit of exposure rate) and compares his results to standard values without concern to the units. Environmental dose rates are given in rem/yr. not R/yr. GM detectors are typically used for surveying gamma/xrays and the scales are appropriately labeled in R/min or R/hr. The detector is sensitive to betas and alpha but in the case it is used for these only counts/minute are appropriate since exposure rate is defined only for gamma/xrays. To convert counts/min to rem/minute you must know specifics of each type of radiation and their relative abundance.

I should add for anyone who later reads this thread and may want to buy a Geiger Counter. The source provide with GM counters is what is know as a check source and only used for assuring that the counter is working properly at least on one scale and is NOT a calibration source and to emphasize that the reading in mR/hr is only for gamma/xrays which may also be only correct for a certain energy range of that radiation. Many GM counters will not detect Alpha or Beta radiation.