Gamma Spectrometry Forum

Hello,

My name is Anthony Marshall and I work as a Radiation Safety Officer and quality assurance for a downhole Well Logging company. I am knowledgeable about the gamma spectrum and am currently am using a sound card system to do experiments with. I do not have any formal education in nuclear physics or anything close, but I have learned a few things over the years. The company I work for manufactures downhole probes with different sensors that measure things like porosity, density, natural gamma, formation resistivities, and more. We are mainly mineral loggers so an average hole depth might be 1500-3000 feet deep.

As an RSO, I have access to many things (like neutron sources) that most people don't. So, I can experiment with different things like neutron activation on my own time. Although I thoroughly enjoy looking at gamma spectra, my hobby is not so much the spectrum but to come up with ideas for downhole exploration. I am currently interested in seeing if I can get a signal back from a LaCl3(Ce) detector over about 500 feet of 4 conductor wireline. I realize this is a tough task using a soundcard, but it is possible using digital signals. We send power and get return signals through thousands of feet of wireline so I'd still like to see if this were possible using basic equipment like analog signal and soundcard as MCA's.

Just recently found this system, so I am still trying to learn how to get the best spectra possible. I hope I can learn from all of you!

Sincerely,
Anthony Marshall

Anthony,

Thanks for the introduction and a somewhat late welcome....

It sounds like you have very interesting work, so i am sure you can get some value from a sound card spectrometer, but failing that I can also help you wist fast digital spectrometers.

Going down a 1500 feet bore hole with a sound card spectrometer would be challenging, because you can't run the coaxial cable that far without distorting the signal. But there are ways to get around it, I once made a system with a Rasperry pi and a battery where you could lower the hole spectrometer and computer into a hole.

That said the sound card spectrometers are not temperature compensated so your spectrum will suffer some drift, which will make all the peaks wider.

My digital spectrometers are temperature compensated and can be configured to record a spectrum directly in the firmware.

Anyway we can discuss this later...

Steven

Hi Steven,

Yes, I am a little late to the party - lol. I didn't even know this sound card method was a thing until about 6 months ago. I was skeptical to say the least, but I would read your forums and I thought I would need to try it. I am certainly not well off and spent way more money on detectors than I should have. But I'm glad I did.

I do eventually I want to try this. I have a winch with about 500 feet of cable used for testing tools and I was going to try that. I've attached some specs on the cable and some pictures that kind of show what they are. I did ask those guys at Theremino if this were possible and they said it could be. They mentioned noise as an issue and explained a few things that might need to be done. The cable we use is a 4 conductor wireline type. It has inner and outer strands and then the four wires. In the past, we have done things like double the wires together if we needed to send power down there. There is a certain tool that you actually send about 80-120 vdc down two paired up wires. You run the negative DC down the cable strand itself. We send and receive digital and I believe some analog signals up from the downhole tool. So, I have no idea if it could be done, but I'd like to try. Just to see what was possible for little money.

The temperature gradient in most places is not as high as you might think. I guess it depends on the definition of 'high'. I know down 500 feet, you will barely get above 25 C. I have some calculation for that somewhere. But yes, as you get deeper, you might get in the 40-50 C range. It's not as bad as most people think. Although the PMT adapter could very well have issues even in those ranges. We are mainly shallow mineral loggers and nothing like the big oil and gas companies. In some of the holes that this could possibly be used, I really don't think it's deep at all.

Yes, it may have to go to digital. I was kind of hoping it wouldn't though. I will fill you in later on what I want to do and you can tell me if you think it would work or not.

Also, if anyone wants to see things involving neutron activation, I would be willing to do a few tests. I control the sources so as long as I'm on my own time, the company doesn't mind.

Anyway, I appreciate you letting me into your forum.

Anthony

Hi Steven,

I managed to do this over 1558 feet of wireline cable! I posted about it in the Spectrum forum. Also, sent you an email

Thanks,
Anthony