BICKEL Gamma Ray Scintillometer

[zidex666]

I am in the process of restoring a client's BICKEL "Algor" Gamma Ray Scintillometer and have reversed engineered the schematic. I am presently awaiting new replacement parts. Will also improve on the circuit topology; specifically the digital counter and the metering pulse shaping circuits. The photomultiplier tube and the NaI(t) crystal in the probe unit are in pristine condition and very sensitive. I would like to contact anyone that has one of the BICKEL units to discover any extant documentation on its operation and a more detailed history.

Though it has some clever design features, it is however a basic gamma ray scintillometer with very limited spectral discrimination capabilities. Its main detection facilities include a 3 in. NaI(t) crystal coupled to RCA6342A Photomultiplier tube. However the probe unit has NO anti-magnetic shield typically made of monel or mu-metal that must surround the photomultiplier tube. Without such a shield the large photomultiplier tabe is susceptible to weak magnetic fields in its vicinity including the earth's magnetic field. It's omission would render any readings from the unit unreliable. The crystal is a standard unit manufactured by Teledyne Brown Engineering. Oddly, despite some of the claims made by others the unit is a crudely made home brew unit. It has a somewhat more complex circuit topology than units made by others such as PRI, Ludlum, Bicron, McFar, Eberline, Detectron, Sopris, etc. It is similar to units manufactured since the late 1940- to 1950's. In terms of sensitivity, it is equivalent to the legendary PRI-111C or a PRI-118 which are available unrestored from time to time on EBAY..

We have been restoring, upgrading, and refurbing vintage Radiation detection equipment for over 30 years.

[Geo]

Try to send an email or PM to Ducati250, but i am not sure if he still reads the forum

http://www.longrangelocators.com/for...ad.php?t=19048.
Also can you attach here some photos from the device??, i like to collect them

Regards

[zidex666]

Geo,

Thanks for the heads up on Ducati. I believe he sold that unit to my client and it appears identical vis-Ã*-vis the photos he posted. I am unable to upload photos of the unit at this time as they are not on a url but on our system. I see no provision on this site to upload pictures from our system onto a posting

Once the unit is fully repaired and upgraded I may put photos and details on a web page and will post a link to it.

Despite previous assertions by J.Player, the PMT and Scintillator crystal are fairly standard fare and are manufactured domestically in the USA. The leading Manufacturer of PMT's today is Hamamatsu in Japan. There also several manufacturers of Scintillator crystals such as Saint Gobain, et. al.

PMT's and scintillators are used extensively in nuclear research and there are literally thousands used to detect emissions of sub-atomic particles in the LHC (Large Hadron Collider) in Geneva Switzerland. The Bickel units are no more sensitive than other scintillator units that have the same spec photomultiplier tube and same sized NaI(t) crystal. In fact such units have been available even to the general public since the 1950's and have been used to find radioactive ore fields, oil, precious metal ores, and even dinosaur bones.

[WM6]

@zidex666: "I see no provision on this site to upload pictures from our system onto a posting "

To upload pictures you should go in Reply down to Options:

Additional Options/Attach Files

[Bill512]

Originally Posted by zidex666

... it is however a basic gamma ray scintillometer with very limited spectral discrimination capabilities...

Hi zidex, I was wondering, has some kind of discrimination or it's just a (sensitive) counter?

[zidex666]

Scintillometers are not counters as such. Geiger counters are, as they count the number of beta particles and in some instances low energy gamma rays that are detected by a Geiger-muller tube, They were in the past measuring CPM or counts per minute. However nowadays their digital meters or analog indicators are calibrated into Sieverts or other units.

Scintillators were traditionally calibrated in MR/HR or milli-roentgens per hour. They do not count ionized radioactive particles per se as with a Geiger Counter but rather measure gamma-ray intensity using various standard energy measurement units.

It is also generally true that the bigger the Geiger-Muller tube is the more sensitive it becomes. The same principle holds true for a scintillator. The bigger the Scintillation crystal the more sensitive the unit becomes. It's much like catching butterflies in a open field with either a net with a 12 inch opening or with a net with a 36 inch opening. Which net do you think will catch the most butterflies if given an equal amount of time?

However one reaches a point of diminishing returns when increasing the size or cross section of a scintillation crystal. Namely "background" radiation. As you increase the sensitivity of a scintillator you increase the level of background radiation proportionately and any signal or signature of interest gets buried in the noise. Kinda trying to listen to an AM broadcast station during the day as you travel away from it. Its signal eventually gets buried in the noise. Naturally occuring ubiquitous thorium radiation in soils particularly in the USA Midwest, radon, cosmic rays, solar flares, hospitals, technicium injected patients, and ionospheric disturbances all contribute to the natural background radiation and limits scintillation accuracy.

Remember there are 3 basic types of ionizing radiation; Alpha, Beta, and Gamma.
Alpha radiation consists of sub-atomic particles and are really helium nuclei. Alpha particles can be blocked or stopped with several sheets of paper and travel about 10 inches or so.
Beta radiation consists of either electrons or negative matter positrons. they are particles and can be stopped by several layers of lead shielding. They can travel several hundred feet until they are absorbed into other matter. Gamma radiation on the other hand is not particle radiation but a ray but on a higher energy level than Light, Ultraviolet, and X-Rays.
Gamma rays penetrate matter and can penetrate a lead shield millions of miles thick. Gamma ray bursts have been detected from black hole events in distant galaxies and within the Milky way.


The only discrimination that's possible from a scintillator other than measuring the intensity of the gamma radiation is to measure its energy bandwidth which can range from several thousand electron volts to several million (MEV) with sophisticated processing electronics such as multi-channel analyzers or by carefully selected analog circuits. However, analog circuits are not very reliable nor very accurate and only yield very coarse indications of detected gamma ray energy levels. The ability to discern differences between gamma-ray energy levels (but not necessarily intensity) is "discrimination".

It is true that certain non-stable elements emit gamma radiation with various intensities but also may emit, for instance for an element X, gamma rays at energy levels of 56KEV, 137KEY, and 2.2MEV simultaneously. Those levels and intensity markers can be used to identify element X and that phenomena is what constitutes some of its "signature." The analysis of those energy levels, intensity, and signature is what is called gamma-ray spectroscopy. However what else is needed for a comprehensive element signature analysis is the inclusion of other signature emissions given off by an element. This includes the intensity and amount of alpha and beta particle radiation which cannot be detected by scintillators.

It appears that the Bickel unit can be roughly calibrated to "discriminate" a certain small bandwidth of detected gamma-ray energies while rejecting others via simple pulse shaping and basic electronic attenuation networks. Whether that is sufficient to accurately identify any isotope or any element below Pb (lead) besides radioactive K (potassium) is questionable or at least suspect at best. Most elements below (lead) have isotopes but are not necessarily radioactive and rarely emit gamma, alpha or beta radiation. If they do, the intensity is so small or the half-life is so short that field equipment would not have the sensitivity to detect it. Furthermore, the percentage of unstable isotopes versus a stable isotope in elements below lead in the periodic table is so small that trying to identify it with a scintillator would be difficult if not impossible. Case in point is measuring the proportion of Carbon 14 in a sample of interest for carbon dating. It would require very sensitive and sophisticated laboratory equipment and chemical reagents to measure. Ditto with trying to identify heavy water from normal water using scintillation.

Hope this helps somewhat.

Regards

[zidex666]

Here's some photos of the Bickel Unit.

Zidex666

Sorry seems this site wants me to reduce the size of the jpg images.
Will re-post later.

[Geo]

Zidex ...thanks for the seminar

[Bill512]

Originally Posted by zidex666

Scintillometers are not counters as such.
Scintillators were traditionally calibrated in MR/HR or milli-roentgens per hour. They do not count ionized radioactive particles per se as with a Geiger Counter but rather measure gamma-ray intensity using various standard energy measurement units.

true, partially,there are some scintillation probes for Geiger's (with CPM "units").
Anyway, my true question was : discrimination or intensity?

Originally Posted by zidex666

However one reaches a point of diminishing returns when increasing the size or cross section of a scintillation crystal. Namely "background" radiation. As you increase the sensitivity of a scintillator you increase the level of background radiation proportionately and any signal or signature of interest gets buried in the noise.

At a given point of space and for a specific "bandwidth", the signal to noise ratio (a radiation source vs background radiation) is fixed , regardless if you carry a scintillation meter ,a Geiger or nothing.

Originally Posted by zidex666

Alpha particles can be blocked or stopped with several sheets of paper and travel about 10 inches or so.
Beta radiation consists of either electrons or negative matter positrons. they are particles and can be stopped by several layers of lead shielding. They can travel several hundred feet until they are absorbed into other matter. Gamma radiation on the other hand is not particle radiation but a ray but on a higher energy level than Light, Ultraviolet, and X-Rays.
Gamma rays penetrate matter and can penetrate a lead shield millions of miles thick. Gamma ray bursts have been detected from black hole events in distant galaxies and within the Milky way.

False 100% ,especially the beta and gamma statements. millions of miles of lead shield ?
Gammas, have a relatively weak interaction with matter in comparison with the alpha+beta, but interacts, and by this interaction we have absorption, attenuation, detection,etc
About these exo-terrestrial gamma sources, the gamma photons travel through (almost) empty space, not through dense matter.

Originally Posted by zidex666

The only discrimination that's possible from a scintillator other than measuring the intensity of the gamma radiation is to measure its energy bandwidth which can range from several thousand electron volts to several million (MEV) with sophisticated processing electronics such as multi-channel analyzers or by carefully selected analog circuits. However, analog circuits are not very reliable nor very accurate and only yield very coarse indications of detected gamma ray energy levels. The ability to discern differences between gamma-ray energy levels (but not necessarily intensity) is "discrimination".

It is true that certain non-stable elements emit gamma radiation with various intensities but also may emit, for instance for an element X, gamma rays at energy levels of 56KEV, 137KEY, and 2.2MEV simultaneously. Those levels and intensity markers can be used to identify element X and that phenomena is what constitutes some of its "signature." The analysis of those energy levels, intensity, and signature is what is called gamma-ray spectroscopy. However what else is needed for a comprehensive element signature analysis is the inclusion of other signature emissions given off by an element. This includes the intensity and amount of alpha and beta particle radiation which cannot be detected by scintillators.

thanks for the big post, I know the limitations of gamma ray spectroscopy- it's not magic but applied science.

Originally Posted by zidex666

It appears that the Bickel unit can be roughly calibrated to "discriminate" a certain small bandwidth of detected gamma-ray energies while rejecting others via simple pulse shaping and basic electronic attenuation networks. Whether that is sufficient to accurately identify any isotope or any element below Pb (lead) besides radioactive K (potassium) is questionable or at least suspect at best...

thanks...

[zidex666]

In response to Bill512:

Yes there are some scintillator probes that can be connected to certain vintage counting units made by such firms as Ludlum, Bicron, Eberline, Eltronics, etc.. and those unit are calibrated in CPM. However most vintage standalone Scintillators are calibrated in the now obsolete MR/HR. There is no standard way to convert CPM to MR/HR conveniently or accurately. It's essentially comparing apples to oranges. Hence new measuring standards are gradually being phased in. The point was that normally the output of a scintillator probe basically measures gamma flux intensity and does not rely on simple counting circuits as in Geiger Counters. so the original posting stands.

" At a given point of space and for a specific "bandwidth", the signal to noise ratio (a radiation source vs background radiation) is fixed , regardless if you carry a scintillation meter ,a Geiger or nothing"

This is only true in an conceptual idealized isotropic environment. Without going into the subtleties of Shannon's communications theory and simply utilizing practicle real world effects, signal to noise ratios are NOT fixed but independently variable. Either the source may be amplitude varying or the Background noise maybe be amplitude and time varying. In either or both cases the signal to noise ration is affected. If the background noise is of greater amplitude than the source signal, the source is swamped out by the background noise. The result is that the signal to noise ratio changes. The examples noted in the original posting are not merely anecdotal but factual in real world environments.

False 100% ,especially the beta and gamma statements. millions of miles of lead shield ? Gammas, have a relatively weak interaction with matter in comparison with the alpha+beta, but interacts, and by this interaction we have absorption, attenuation, detection,etc About these exo-terrestrial gamma sources, the gamma photons travel through (almost) empty space, not through dense matter.

Not false! However your statement:

"Gammas, have a relatively weak interaction with matter in comparison with the alpha+beta, but interacts, and by this interaction we have absorption, attenuation, detection, etc."

This is generally correct. However any interaction depends on the gamma flux intensity. The greater the intensity or energy flux the greater the interaction with matter per unit volume. Case in point is that ionizing radiation, gamma, x-ray radiation in a nuclear explosion would make even the efficacy of massive lead shielding in a blast zone moot even if thermionic forces don't incinerate any of the lead shielding. The point here in my original posting was to basically differentiate between the various kinds of ionizing radiation for the laymen and the instrumentalities used to detect them. Therefore what's the point of your comment? My posting was not meant to be a comprehensive treatise on nuclear or quantum physics. What I had in my posting stands!

But, thanks for the kudos.

I know the limitations of gamma ray spectroscopy- it's not magic but applied science.

Absolutely agree! It's indeed not magical but applied science.

Regards.

[Bill512]

Originally Posted by zidex666

In response to Bill512:

Yes there are some scintillator probes that can be connected to certain vintage counting units made by such firms as Ludlum, Bicron, Eberline, Eltronics, etc.. and those unit are calibrated in CPM. However most vintage standalone Scintillators are calibrated in the now obsolete MR/HR. There is no standard way to convert CPM to MR/HR conveniently or accurately. It's essentially comparing apples to oranges. Hence new measuring standards are gradually being phased in. The point was that normally the output of a scintillator probe basically measures gamma flux intensity and does not rely on simple counting circuits as in Geiger Counters. so the original posting stands.

I've got my answer regarding the Bickel instrument (Disc or intensity).
However is true that the output of a scintillation tube is pulsed voltage directly related to the initial product of the NaI(T) photons? (photoelectric superimposed in compton).

Originally Posted by zidex666

This is only true in an conceptual idealized isotropic environment. Without going into the subtleties of Shannon's communications theory and simply utilizing practicle real world effects, signal to noise ratios are NOT fixed but independently variable. Either the source may be amplitude varying or the Background noise maybe be amplitude and time varying. In either or both cases the signal to noise ration is affected. If the background noise is of greater amplitude than the source signal, the source is swamped out by the background noise. The result is that the signal to noise ratio changes.

was necessary to mention the (trivial) note, that the source's are constant in time in this case? my intention was to be a simple example.
Now, lets see the more realistic cases.
Any time variance of the sources flux, has effect on the noise to signal ratio but this has nothing to do with any detector.
Let the ratio be variable all the time, with whatever function you like.
The point is that the "ultimate" (barrier) signal to noise ratio is a property of the space it's self, and not instrumentation related.
As you make an instrument more and more sensitive there is a point beyond that any improvement in terms of sensitivity is useless.
This is not because the signal then is buried in noise as in your statement: "..As you increase the sensitivity of a scintillator you increase the level of background radiation proportionately and any signal or signature of interest gets buried in the noise.."
This is simply because, beyond this point you amplify the signal as well the noise - so, no real benefit except signal scaling.

Originally Posted by zidex666

Not false!

sorry, but these "millions of miles of lead shield" was to shield the gamma radiation of a cosmic event in the order of magnitude of the bing bang?


anyway,many thanks for the Bickel info and the nice talking.
this instrument was mysterious, not to say (almost) mythical...
Bill

[zidex666]

Please find attached Photos of the Bickel unit including the Probes internals.

[Geo]

Thank you very much

BTW... why there is isolation tape around the tubes???

[zidex666]

The black tape serves three main functions:

It provides shielding against light entering the photomultiplier tube. (You only want light or photons emitted by the crystal to enter the photo the top of the photomultiplier tube.)

It crudely binds the NaI(t) crystal holder to the top of the photomultiplier tube.
Unfortunately the Bickel probe did not have any optical grease between the photomultiplier and the crystal holder when it was disassembled. This is bad practice as stray humidity will fog up the junction between the photomultiplier and the crystal. It testifies that the unit's probe was constructed in a home-brew Rub-Goldberg fashion.

Thirdly, on top of the first layer of tape, a crude and cheap lead shield made of a cut-up sheet of photographic "FilmShield" was wrapped around the Photomultiplier tube. Whether this simple lead shielding had any significant affect while prospecting or searching for certain radioactive isotopes is uncertain. If anything it may provide limited shielding of neutron radiation.

Perhaps the most significant shortcoming in the probe's construction is the complete absence of any anti-magnetic shielding. Photomultiplier tubes are extremely susceptible to stray magnetic fields and can seriously affect their operation and accuracy. In fact even the earth's magnetic field can be a problem in rendering accurate readings. Inspection of the inside of the probe's outer casing revealed no such shielding. Anti-magnetic shields are encased around photomultiplier tubes and are typically made of Monel or mu-metal and are fairly ubiquitous in scintillator probes. In general, the lack of anti-magnetic shield in the probe makes one question the Bickel unit's efficacy in actually identifying radioactive isotopes.

Notice that in one of the photos that the tape was removed from the PMT and the crystal holder. The PMT is of USA (RCA) manufacture as is the NaI(t) hermetically sealed crystal holder made by Teledyne.

NaI(t) crystals are extremely hygroscopic particularly when exposed to humid air. If exposed in an environment with any humidity they quickly turn yellow and opaque rendering them useless. NaI(t) is also extremely toxic. Crystal holders produced in the 1950's often turned the crystals yellow and opaque after two to three years because they were sealed using rubber O-rings which quickly deteriorated and allowed water vapor inside the crystal housing. Later in 1960's onward they were hermetically sealed by almost all manufacturers. Notice that in the photo where the crystal holder is separated from the PMT, the crystal if absolutely clear and Not opaque.

We will rebuild the entire probe unit and bring it up to modern specs.

Hope this helps.

Regards.

[Bill512]

thanks for the update zidex.

Originally Posted by zidex666

...Thirdly, on top of the first layer of tape, a crude and cheap lead shield made of a cut-up sheet of photographic "FilmShield" was wrapped around the Photomultiplier tube. Whether this simple lead shielding had any significant affect while prospecting or searching for certain radioactive isotopes is uncertain. If anything it may provide limited shielding of neutron radiation...

about this crude lead thin shield, it is wrapped also all around the NaI(T) crystal??

[zidex666]

about this crude lead thin shield, it is wrapped also all around the NaI(T) crystal??

No. It's width is not wide enough to envelope the entire glass housing of the PMT. It does however, short that it is widthwise, wrap around only the PMT. It's presence though is puzzling. The only reason that would make sense is that it is to shield it from a large flux of neutron radiation. Even so in real world environments lead shielding on a PMT is unnecessary. More important for PMT's is anti-magnetic radiation shielding.

It does NOT wrap around the Crystal housing!

Regards!