R & D Progress on Autonomous Spectrometer

[Sesselmann]

Hi All,

Here is an R & D project I have been hacking away at for almost a year, it is now getting close to a workable product.

It's a recording spectrometer, and it's intended use is for well logging. Operating this detector requires no skill at all you simply switch on the power and wait for the detector to boot, indicated by a yellow light, to start recording a spectrum you press a button which changes the indicator light to red, the detector is now recording a continuous wav file up to 4 hours to SD ram.

The detector has inbuilt WIFI so once the recording is complete the sound file can be retrieved and opened up in PRA for analysis.

I suspect not everyone is aware that PRA can obtain pulse shape, open and read WAV files, this is a really cool feature.

Once the file is open in PRA you can look at specific sections of the recording by selecting the time range in the Data acquisition and analysis panel, this method would be useful for geologists to analyse rocks at various depths, all they would need to do is manually note the depth of the detector at specific intervals.

The detector is constructed from 40 mm carbon fibre housing with machined aluminium ends.

The circuit board is a custom design board with integral high voltage, preamp, sound card and Rapberry Pi-ZeroW. It took three versions of the board before I got it right, but that's about average for me.

This is how it looks when it boots up and shows the yellow light, it takes less than one minute.

The red indicator means it's recording.

This chart is made in Excel from a 250 second recording, histograms exported at 50 second intervals, during recording I swapped the sources from Cs137 to Co60 to show proof of concept. The resolution is is not great because I have used an old yellow Russian crystal in the prototype, but it's adequate for the experiment.

If there are any geologists reading this I would be interested in feedback and maybe even making another prototype for field testing.

On a side note it would be worth asking Marek if he would consider adding a z axis with time intervals so one could show a 3D spectrum directly in PRA.

Steven

[lodovico]

Great work !

[sgt_bear]

Very nice project!

[Geoff]

I'm assuming this would be for wireline well logging? I know that composite housing wouldn't hold up to logging while drilling applications. All of our detectors were housed in aluminium alloy and had to be able to withstand 50g shocks, vibration and flexing, and temperatures up to 175C. The wireline tools, which work on open holes, are able to be much more sensitive as they aren't seeing the same severe operating environment.

[Sesselmann]

Geoff,

Thanks for feedback, I was imagining that this detector would go inside another tube, but I really need to do some more research on how this is done. I doubt it would be practical to have it inline while drilling, the vibration would kill the PMT.

Steven

[luuk]

Nice project Steven,
But Like Geoff says you also have to think of high temperatures in well logging, we use special tubes and vd's for it , if not they won't survive.
Luuk

[Sesselmann]

This is a proof of concept only, and it should be a trivial matter to make a more robust housing, especially for the detector part. The electronics may be better housed on the carbon fibre tube as the WIFI antenna may not work in a metal housing.

Voltage divider with high temperature resistors also not a big problem, not sure how LiPo batteries can handle high temperatures may need to investigate further.