> The Cogamo detector is a small (23 cm × 28 cm × 10 cm) and lightweight (3 kg) radiation monitor, using a CsI (Tl) scintillator (5 cm × 5 cm × 15 cm) coupled with a Silicon Photomultipliers (SiPMs) MPPC (Multi-Pixel Photon Counter) as a photo sensor (Figure 1b). The energy range for gamma-ray spectroscopy is the ∼0.2–10 MeV band. The detector acquires the energy deposit and arrival time of each radiation event and records them into a microSD card. The time tagging is performed using GPS signals. In addition, 20-s bin count rates in six energy bands for 0.2–0.5, 0.5–1, 1–2, 2–3, 3–8, and >8 MeV, GPS status, ambient temperature, humidity, and optical luminosity are recorded on the microSD card and are also sent to the web server for a quick-look purpose. An observation is started simply by connecting a GPS cable and a power cable and then turning on the power switch. Energy calibration of the Cogamo detector was performed for each file of one-hour data when analyzing, using environmental background radiation lines of 40K (1.46 MeV) and 208Tl (2.61 MeV).
Is the state of IOT such that these kinds of sensors and measurements are widespread and reasonably priced? Where can I learn more?
More or less. What do you consider reasonably priced? The sensors aren't particularly special. PMTs are used widely in science for photon counting, but maybe the ones they chose have some specific characteristics.
Most of this system is very fast readout circuitry - fast ADC. You need an FPGA to get the data off at 12-bit 50MSPs.
The expensive stuff is probably the PMTs from Hamamatsu and the power supply from Matsusada. They will certainly give you a quote, but their sensors can be pretty pricey. Probably hundreds each for the PMTs and that again for the power supply. Hamamatsu are the experts and they have a good monopoly. Edmund sell some pre-packaged tubes for example: https://www.edmundoptics.com/f/hamamatsu-photomultiplier-tub... (but Edmund are always $$$)
Everything else is glue really, with a custom PCB for the data capture. Though some of the components like the FPGA and the ADC are $50 each (and there are two ADCs). I don't know if they would release this open source, but I suspect not (which is a shame).
As is typical with science, the authors emphasise how they designed this to be a low cost system, but never actually say how much it cost. I would hazard a guess that you could do this for under $5k BOM cost (ignoring design and labour) if you planned it well. Let's say $500-1k for a crystal with some provenance, $2-3k for optics and $1k for the circuitry and housing. Might be well off on the crystal if you have to buy it from somewhere reputable though. You could probably MacGuyver something for a lot less if you could get away with bits from eBay.
With a bit of creative scrounging you could put something together for less than US $100, I imagine. The budget would probably be driven by the question of whether the surplus pager scintillators are sensitive enough to observe the effect.
As soon as you're into surplus for sourcing parts you've essentially done an end-run around your target pricing: it will work, for a very limited run and then you find the 'true cost'.
What would probably be better is to see what design limitation crop up if you try doing it for say $1000 without any surplus parts.
Yep, a lot depends on the size of the 'production run.' The seller had over 3000 of those scintillators originally, not clear how many they have left.
Digitization is another question -- they used a fast FPGA-based digitizer but it's not clear why it was necessary given the duration of the events being recorded. If it really is needed, then driving the cost down on the digitizer will be as big a challenge as the scintillator itself.
That's a neat little stash then! Wonder where they got them. I used to frequent government surplus auctions and the weirdest stuff would turn up. 10 tons of spare parts for a Magirus-Deutz vehicle that hasn't seen active service since the 50's, five containers full of used army boots (but without the containers), a veritable mountain of laptops sans harddrive and with various unknown defects and so on. I would occasionally buy something and usually got something out of it (profit, some useful tool) but on the whole the quantities of the lots were such that only people with both lots of space and lots of money at the same time would be serious bidders on those lots.
Even working as a scientist, I buy equipment from eBay. If you bide your time, you can find useful bargains. In fact, even when my budget can accommodate new gear, there can be exceptionally long lead times, whereas an eBay seller has it on hand and will ship it out tomorrow.
This makes it harder to copy a documented design, of course, but most of the time a scientist with a knack for gear can adapt things as easily as copying them.
Also, people did photon counting for a long time without 50 MHz ADC's, just saying. ;-)
it's not using PMT's it's using silicon photomultipliers, those can be had in the $5 to $10 range. At first sight the most expensive part seems to be the CsI crystal.
Perhaps polystyrene or PMMA or another transparent plastic could serve as a cheaper alternative, but probably at the cost of energy resolution, although this study binned the energies anyway.
The collaboration has been measuring since ~2016 at least, so they have multiple generations of sensors installed. You capitalize and emphasize "the arxiv Paper" as if the group published one paper only as if they are from then on forbidden to explore other sensor constructions.
The parent article describes a more recent iteration using silicon multi-pixel photon counters (MPPCs aka Si"PhotoMultipliers" SiMPs).
When I said $5 to $10 range I was referring to some of these for example (did not thoroughly search for the lowest priced across distributors right now):
The 2007.13618 Thundercloud Project paper is excellent and has a fairly thorugh breakdown on the various bits of hardware and crystals used at different iterations of the project.
No detailed costings (save for the raspberry pi, mobile card + plan (to remotely relay data)) but a good guide.
As with all such projects I dare say the software costs were $0 being measured in graduate student time.
> The Cogamo detector is a small (23 cm × 28 cm × 10 cm) and lightweight (3 kg) radiation monitor, using a CsI (Tl) scintillator (5 cm × 5 cm × 15 cm) coupled with a Silicon Photomultipliers (SiPMs) MPPC (Multi-Pixel Photon Counter) as a photo sensor (Figure 1b). The energy range for gamma-ray spectroscopy is the ∼0.2–10 MeV band. The detector acquires the energy deposit and arrival time of each radiation event and records them into a microSD card. The time tagging is performed using GPS signals. In addition, 20-s bin count rates in six energy bands for 0.2–0.5, 0.5–1, 1–2, 2–3, 3–8, and >8 MeV, GPS status, ambient temperature, humidity, and optical luminosity are recorded on the microSD card and are also sent to the web server for a quick-look purpose. An observation is started simply by connecting a GPS cable and a power cable and then turning on the power switch. Energy calibration of the Cogamo detector was performed for each file of one-hour data when analyzing, using environmental background radiation lines of 40K (1.46 MeV) and 208Tl (2.61 MeV).
Is the state of IOT such that these kinds of sensors and measurements are widespread and reasonably priced? Where can I learn more?