Gamma ray detectors

[DRAKOS]

Hi to all treasure hunters.
I read that there are radio nuclides of all elements, including gold, ( Au 195, Au 198, Au 199 etc.) What is your opinion about gamma ray detectors? The energy of these Au radio nuclides is big enough for detection by a gamma ray detector. But how deep, gold could be in to the ground, so that its gamma rays could be detected , by such a detector? Any ideas? Tasos.

[wyndham]

Problem i hear is that Gamma rays go thru about eveything. So if you had a detector it might be from 2" 2miles or 2 light yrs away signal.
Wyndham

[Max]

Hi to all treasure hunters.
I read that there are radio nuclides of all elements, including gold, ( Au 195, Au 198, Au 199 etc.) What is your opinion about gamma ray detectors? The energy of these Au radio nuclides is big enough for detection by a gamma ray detector. But how deep, gold could be in to the ground, so that its gamma rays could be detected , by such a detector? Any ideas? Tasos.

Hi,
radio nuclides of Au are not easy to find in nature cause they need nuclear reactions to be created from stable isothope of gold. They could be found in some lava in really small percentages with other heavy metals and radioactive materials.
Gamma-ray camera doesn't need external radio-nuclides to work...but a (controlled) and shaped "internal" source of gamma-ray that is opened just before the scan need to be performed by operators. Gamma rays can penetrate easy the ground...rocks...etc etc...and sensors could be special CCD devices that just see gamma-rays interactions on their sensible surface(s). Usage is restricted to military and they aren't civilian applications (at least as I know). CSIRO mining in Australia has a prototype of one that is used in mining operations...
They are all very dangerous apparatus...and need extreme care to avoid harms on operators (and environment too).
Also gamma-ray camera have no discrimination but just absorment statistics that could be displayed to give 3D info of objects underground based on different reflection/adsorbing properties of different minerals etc.
All modern systems are strictly controlled by computers and signals aren't just displayed as they are but elaborated to give more informations that otherwise human eye cannot evaluate.

In brief: no gold disc could be made just using a straight-camera (no computer); no gold detection or disc could be made by using gamma-ray detectors (e.g. geiger tubes, ionic chambers and the like) cause gamma-rays are always the same...no matter what produce them!

Best regards,
Max

[DRAKOS]

http://www.nucsafe.com/Products/identispec.htm

First of all, I want to thank you both for your answers. But take a look to the adress above. What is your opinion about that? I think that Au could be detected like the other elements shown.Most of them are not really radioactive.The discrimination is available, because every element's gamma ray, has different energy status. Isn't that right?

[Max]

http://www.nucsafe.com/Products/identispec.htm

First of all, I want to thank you both for your answers. But take a look to the adress above. What is your opinion about that? I think that Au could be detected like the other elements shown.Most of them are not really radioactive.The discrimination is available, because every element's gamma ray, has different energy status. Isn't that right?

Hi,
energy of photons is related to their frequency. Gamma emission has a wide spectrum of frequencies...and that's right. Every transition from an energy level to other (lower) levels could give photon emission (not only gamma ray - just so called "quantum" of energy). So yes...in a controlled environment/lab emission could be traced to give informations on composition of emitting source. Problem is that there are other interactions in real world that make impossible to discriminate what the source could be ...even a plant root could emits gamma-rays if proper conditions are meet...but then disc what's the secondary source (metal-ion or whatever organic compound...) is another story. Natural occurrences of rad-Au nuclides is too low to be detected in many places without samplings and in-lab analisys (where they are present). Secondary radiations (due to other incident radiations) are completely unpredictable and really hard to selective insulate individual sources. At the end...if conditions are "good" you could end-up with an infinite continuos spectrum that haven't any peak above the others and so just saturating the digital sampler connected to the CCD sensor.
So is just impossible using that "trace" photons to detect anything , anywhere.

Best regards,
Max

[DRAKOS]

Thanks Max, you were quite clear.

[Max]

Thanks Max, you were quite clear.

Hi Drakos,
sorry...had trouble with internet link in last few days and just see now your reply.
I forget to mention that in radioactive elements e.g. gold isothopes that are mentioned earlier in the post... some gamma photons are generated by mutation due to nature of these unstable atoms.
This is expecially true for gold e.g. Au-198, with half-life of 2.697 days, produce approximately .411 MeV of gamma radiation.
You could find more informations e.g. on wikipedia too about unstable isothopes of gold.
Of course, this topic is of few interest here cause these kind of stuff is really hard to find in nature and is almost all produced by human activities by nuclear processes e.g. for investigating and cure some cancer or in nuclear physics lab.

Actually, gamma-camera devices use just their own source of gamma-rays to investigate the operating environment, cause also bradband sensors for that frequencies are almost impossible to be made.

Best regards,
Max

[DRAKOS]

Hi Max.
Look to this site.It's interesting.I tried to contact them, but their e-mails are not in use. They mentioned AND commercial use for private projects. But I can't contact.
Tasos.http://www.csiro.au/files/mediaRelease/mr2001/Prlandmine.htm

[Max]

Hi Max.
Look to this site.It's interesting.I tried to contact them, but their e-mails are not in use. They mentioned AND commercial use for private projects. But I can't contact.
Tasos.http://www.csiro.au/files/mediaRelease/mr2001/Prlandmine.htm

Hi,
yes it's the company I've mentioned (from australia). Don't know if they have finished the project and actually sell the unit.
I'll check it out.

Best regards,
Max

[DRAKOS]

Thanks Max, I'm waiting.

[Max]

Thanks Max, I'm waiting.

Hi,
it's the same article I saw some time ago.
No news as I can see.

Best regards,
Max

[J_Player]

Gamma Ray Detectors

Gold, copper, silver, oil, and water have been detected at long range with isotope detectors for more than 20 years. There is a NAI scintillator detector that is capable of pinpointing large ore deposits buried up to 5000 feet deep, measuring only the natural radiation from the deeply buried ores. These detectors have been in use by oil exploration companies and mining companies for nearly 3 decades. These machines work by sensing slight variations in the natural background radiation, and they are able to recognize the signature for these different elements because every element has it's own unique gamma signature corresponding to the different gamma energy given by their nuclides. While these detectors are sensing very weak natural gamma emanations from elements under the ground, even these small amounts can be classified using standard gamma spectroscopy techniques.

There is only one Gamma detector that I know of which was built specifically for finding common minerals under the ground without irradiating them artificially. This is the Bickel isotope detector. From the time it was invented nearly 30 years ago, there is still nothing available today that can do what these machines can do. His machines used a NaI scintillator crystal with several photomultiplier tubes to sense all the background radiation that entered the open end of a lead tube. The signal from the photomultipliers was sent through signal processing electronics to measure total gamma detected, and also to extract the gamma signature for the element that he was searching for (such as copper, gold, or silver). This signal was identified the same way that gamma spectroscopy identifies an element. In the case of gold, he only looked for the stable gold nuclide 79Au196. He would map an area of land in a grid pattern, driving or flying over the area while recording the total gamma counts and the gold counts on a chart recorder. Then after gridding the area, he would print a map with the count values and interpret the results to determine where the deposits were located. Usually he was pinpointing petroleum deposits or copper ore deposits. To say that this method cannot work is incorrect, because it has been done on a routine basis for the past 3 decades. It is a little known technology because few people are familiar with the methods to construct these sensors that are capable of measuring natural background radiation anomalies, and also few have the knowledge of subterranean geology that is necessary to interpret the readings from the sensor.

It is true there are many stray background gamma waves coming from all directions, and the majority of them will not be coming from an ore target under the ground. But the presence of a large ore deposit is enough to skew the background concentration of the target element and provide useful information for locating the target. People who have performed these grid surveys have also discovered the importance of knowing what underground geologic formations will skew the readings, and they know to make corrections for these influences as well as other influences that could add noise to the signal.

Even though these detectors are about 30 year old technology, with many discrete components that are no longer used today, there is still no detector that is capable of locating as they do. But recently, there have been a number of technological advances that would make these machines much easier to build and calibrate. Needless to say, today's electronics can eliminate over 80% of the components that are used to count and drive numeric displays. But there are also new improved gamma sensors that do not need photomultiplier tubes.

The new CZT sensors are more than twice as sensitive as the NaI crystals, and they create a direct electronic signal output when a gamma wave passes through them. They are inexpensive enough that they are being developed in arrays which will greatly improve the directional properties. There are also arrays being developed that will sense medical xrays and display an image without the need for developing film (similar to how a digital camera works). These CZT devices appear to hold a lot of promise in the future of gamma ray sensing and spectroscopy. I expect to see this technology become prominent in this field within the next few years.

Some current uses in the field of natural isotope detection are in satellites and space probes that measure the composition of the soil on the Earth, Venus, Mars, and other planets as well as elements from distant stars. Nasa is also looking into the new CZT gamma detectors for future space probes.
See these links:

http://imagine.gsfc.nasa.gov/docs/sc...lid_state.html
http://imagine.gsfc.nasa.gov/docs/sc...tillators.html
http://www.engin.umich.edu/alumni/en...ter/index.html
http://grs.lpl.arizona.edu/curricula...aProject4.html (click on the demo button).


These natural gamma detectors are also used in geotechnical studies for Oil companies and mining operations. Here is one company that sells several scintillators including a probe to be lowered in a bore hole to take measurements of the elements that make up petroleum:
http://www.giscogeo.com/pages/giscorad.html

Keep in mind, these detectors are not designed to sense dangerous amounts of radiation hazards, or elements that have been artificially irradiated in a laboratory. They are specialized for looking at very small traces of gamma radiation that are part of the natural background found on the surface of the earth, or other planets or distant stars. They are used to identify what elements exist in these places where they survey. This is only a small segment of the gamma spectroscopy field. There is a much larger market for gamma sensors used to detect radiation hazards and gamma spectroscopy used in laboratories to identify unknown substances as well as medical laboratories.