A sea of sparks: Seeing radioactivity

I have considered

* scanning a linear array of BPW34 photodiodes, in a similar spirit to a scanner to cover a plane, each photodiode going to its own "MCA circuit" (TIA->cheap audio codec like those from Everest Semi). Either direct measurement of generated charge pulses or covering the photodiode with phosphor on aluminum foil or so

* cloud or bubble chamber (cloud chamber is less dense and will generate fewer events, so probably bubble chamber): instead of needing a large 2D or 1D array of parallel circuits, we image and track generated charged particles and use the trajectory starting end (less curved) to determine the source direction!

* consider X-ray crystallography, an incoming straight beam can diffract in many directions on a monocrystal. rotating say a silicon wafer, and measuring the incoming photon energies with one or more photodiode/MCA circuits we can assign a source likelihood distribution by keeping track of the orientation of the monocrystal. akin to sparse sampling but instead of masks its diffraction patterns.

If you have better ideas or variations in mind, let me know!

Russians, South Africans, USAians, et al all run crews - we (Australia) have done Australia, Mali, other African regions, all of Fiji (many islands), India in May 1998 (the Pokhran-II nuclear test sites as they happened), and elsewhere.

The data is one thing, processing raw spectrometer data is a whole other thing - calibrations, corrections, dead time, etc.

See: Grasty / Minty GUIDE TO THE TECHNICAL SPECIFICATIONS FOR AIRBORNE GAMMA−RAY SURVEYS https://www.ga.gov.au/bigobj/GA7667.pdf

Off hand, I'm not familiar with any public facing portals for downloading raw data.

Bear in mind, these are "snapshot" static, historic, broad area spectrum maps - they're not live, they won't show new leaks, changes, etc.

They are, however, "training data" for forming a kernel of a NASVD - Noise Adjusted Singular Value Decomposition - a bundle of all the major features of typical regular environmental radiation for some locale.

If you fly about or have an instrument taking live readings and subtracting a normalised background kernel .. you get the faint trace "weird arse stuff" lighting up instead of being buried.

Finland's the home of the NASVD author, the country used to run "find a barrel of waste" in a forrest compitions back in the day, they're adjacent to some radiometrically filthy submarine docks and pens just over a border.

The game goes thus - fly at about 70m/sec about 80m above the deck in some kind of frame carrying 30 to 40 litres of doped crystal packs .. and pick out a signature in near real time from one second spectrum windows.

They have data, I don't know about portals.

https://www.helsinkitimes.fi/finland/finland-news/domestic/2...

Can confirm, though, Cresco STOL's make a good platform: https://www.youtube.com/watch?v=1_MO5Wfomks

  The EUropean Radiological Data Exchange Platform (EURDEP) consists of data exchange mechanism and presentation website for radiological monitoring data which is collected and shared by 39 participating countries in almost REAL TIME.

Certainly useful for a mapping European normal background, the details under the hood could be a pain (types and formats of data, etc), it's historic and ongoing chronological data for distributed fixed points.

Their interactive public play map is normalised(?) raw total counts, _not_ a spectrum of gamma events bucketed by energy - ideally they are also recording and sharing full spectrum data at some stations in their network .. and making that publically available.

Of possile interest:

* https://www.abc.net.au/news/2022-08-10/hedley-marston-marali...

* https://www.wakefieldpress.com.au/product/fallout/

Do you have access to a high bandwidth oscilloscope? do you observe the expected exponentially decaying pulses? Sound like you could debug your circuit to find out what is happening.

For higher energies on would want to use a thicker intrinsic region, one approach I have considered would be to use a distant aperture, so that the direction of incoming rays is known, and then tilt the photodiode so that the rays can experience a much longer path in the intrinsic region (so that when a photon generates a high energy electron, the stopping length can be attained without clipping / aliasing the energy resolution as much). Basically tilt the photodiode so that its plane is closer to parallel (or exactly so). There is a trade off between cross section (fewer events) and maximum energy measurable, one can compensate for the lower cross section by having more photodiodes.

all 3 proposals would be passive, including #3, so it wouldn't emit X-rays, just detect them and build up a self-consistent picture that explains the observation statistics for each event (with that energy and time/orientation of the silicon wafer).