Improvements to ion Chambers

In recent months research into the ioni Chamber for Radon have led to unexpected results and new discoveries. Part of these discoveries are credit for experimenters, around the world, the most active is definitely Pavel Provaz, He has already experienced a great number of different configurations (and invented the new single wall version). On this page we list the results of the most recent comments.

Many people have experienced that the room, After running a long ago, suddenly loses sensitivity and, After some time, starts working fine. And have questioned whether it can depend on high-voltage variations, or other parameters.

ANSWERS
I HV nothing to do, may vary from 450 to 550 Volts without causing differences in measurements.

And even tension on the TP1 is insignificant, depends very much on the FET. Some FETS have a current (with Gate open) highest and then the TP1 salt a little. But the tension on the TP1 salt also, and very, in the presence of moist air. And under these conditions the FET amplifies less.

So these flaws are almost certainly caused by air humidity.

In recent months we have discovered that the air over the 70% RH can lead tens of pico Amps (and up to over 500 PA when you get close to 90%). We are therefore studying a room that can work even in very humid environments (Besides, no rust)

The first solution was to dehumidify the air (that you send to the Chamber through a pipe and a small fan). The dehumidifier consists of a serpentine carved on one side of a piece of aluminum from 5 x 5 cm and up 10 mm, with a Peltier cell that cools it. The coil is facing down and a cloth collects water drops and evaporates.

But the dehumidifier is not a very elegant solution and consumes a lot of power. For which we are studying some solutions for moisture and some improvements, for other aspects:

  • First of all a central electrode in 2 mm brass tube (that greatly improves resistance to mechanical noise)
  • An external wall made of stainless steel or aluminum.
  • New pattern of polarization of the FET Gate FET grounded through resistor from 1 Gig Ohm bearing hundreds of air leakage current picoAmpere.
  • New circuit amplifier (version 6).
  • Attempts to eliminate the double wall, loading the Central pad with 500 Volts (about) and isolating the Gate with capacitor 1000pF.

A cool new idea is to protect the ions from moisture by closing in a polyethylene bag. Polyethylene stops is the water vapor that Thoron, but lets move on Radon. The polythene bag acts as a polymer membrane (radon has first to dissolve and then spread) It must be very thin to not impairing the response.

Those wishing to do experiments, may write to Alexis, who knows where to find the components and can prepare new PCB.


New amplifier – Version 6

IonChamberAmpV6_SCH IonChamberAmpV6_3D_Bottom

From here you can download the pattern, the PCB and the latest simulations:
http://www.theremino.com/files/IonChamberAmpV6.zip

And here you can buy cheap resistors 1 Giga:
http://www.mouser.it/ProductDetail/TE-Connectivity/RGP0207CHK1G0/?qs=%2fha2pyFaduhkrdcbzNk6CHQ1bfgoVndRtlEgfJiN2nuM8RBuTFoG3A%3d%3d

Sure that the resistor must be COMPLETELY INSIDE the inner Chamber, otherwise collects complaints and does not work anymore.

Note that if you polarize to mass the Gate tension on TP1 becomes about 0.3 Volts and will no longer be modified by moist air (before the normal voltage of TP1 had 1.1 to 1.3 Volts and saliva very, even beyond 1.5 Volts, in the presence of moisture. And when the voltage on the TP1 salt, the FET amplifies less, and there is a strong loss of sensitivity to low amplitude pulses. Why there are fewer impulses.

The latest versions also include a regulator LM385 which further reduces (In addition 30 times) the noise coming from USB. This improves the functioning on some particularly noisy PC.

The most recent research has shown that a strong air humidity, as well as conducting a stream of hundreds of picoAmpere, It also causes rapid variations of current. These changes result in a loud noise on top of the impulses (visible on TP3 with an oscilloscope). Everything is amplified by the presence of dust in the air (the powder gets wet and increases noise)

We don't know so until humidity level you can get, but we're pretty sure that, beyond the 90% of moisture, the disturbances become that breadth, that no room at ions, However that may be built, might work.


New high voltage power supply – Version 5

Hv475_V5_SCHHv475_V5_3D_UpSchematic and PCB power supply dell ’ version 5, with traditional components.

Hv475_V5_SMD_SCHHv475_V5_SMD_3D

Schematic and PCB power supply dell ’ version 5, with surface mount components.

Adding a remote controller 3.3 High voltage ’ Volt will prevent l from being disturbed by noise from the USB. The baseline which is measured on the TP3 is more stable and more precise measures are then. On some PC with USB voltage very noisy this new power supply can make big difference.

With this link you can download the pattern, the PCB and simulations, both the ’ amplifier power supplies, in both SMD with classic components: IonChamberCircuits



“Concentration” or “Activity”, That's the problem!

Until a few months ago, we measured the “Radon concentrations”, whereas now we measure in “Radon Activity”. We had to adapt to this custom to give similar values to other Radon measurement devices on the market.

To calibrate the ions in “Radon Concentration” the value to set is 2.15 CPS/Bq/l. With this adjustment the values in Bq/l and Curie/l will be about five times lower.

To calibrate the ions in “Radon Activity” the value to set is 0.43 CPS/Bq/l. With this adjustment the values in Bq/l and Curie/l will be similar to those measured with other devices on the market.

In European Commission report There are excellent definitions of two units of measure.

  • "With “measurement of concentrations of radon” refers to the number of disintegrations of the isotope Rn-222.
  • The term "exposure to radon" means the exposure to radon progeny. "

Given that we convinced ourselves, If everyone uses the activity will we. We want to point out, however, that “should” measure the “Radon concentrations” and give values about five times lower, come suggerito da tutte le organizzazioni internazionali.

Documentazione che suggerisce di usare la “Concentrazione”

Sia “Word Health Organization” che la “European Union” suggeriscono di usare la “Radon concentrations”
https://www.uic.edu/sph/glakes/radon_measurement/pdfs/unit_three.pdf
http://www.atsdr.cdc.gov/PHS/PHS.asp?id=405&tid=71

The World Health Organization has recommended a radon reference concentration of 100 Bq/m3 (2.7 pCi/L).[82] The European Union recommends that action should be taken starting from concentrations of 400 Bq/m3 (11 pCi/L) for older dwellings and 200 Bq/m3 (5 pCi/L) for newer ones.[83]
http://en.wikipedia.org/wiki/Health_effects_of_radon#Radon_concentration_guidelines

Radon concentrations in the air are measured as the amount of radioactivity (Bq) in a cubic metre of air: http://www.who.int/ionizing_radiation/env/Radon_Info_sheet.pdf

The concentrazione di radon si misura in Becquerel per metro cubo (Bq/m3 ). Il valore di 400 Bq/m3 indica la disintegrazione di 400 nuclei atomici di radon al secondo in un metro cubo d’aria accompagnata dalla emissione di radiazioni ionizzanti.

Radon concentration stairs
http://en.wikipedia.org/wiki/Radon#Concentration_scale

But then why all manufacturers of similar devices use the “Radon activities”?

Probably because this causes you exceed the limits of the law and it becomes easier to propose costly remediation. This is only a supposition, but until someone suggests a better explanation…

.


An ion Chamber “embedded”

Alessio has developed an ion Chamber with all software in a PIC Microcontroller. This solution is especially economical because it does not require a PC (or tablet).

Radon Detector Embedded

With one button you maneuver all functions. The display shows the version, currently “Radon Detector Ver. 1.0”, the seconds elapsed and the concentration of Radon gas in Bequerel per cubic meter.

  1. Livio says:

    William wrote:
    I have experienced a loss of sensation around four times, in conditions of dry air (about 50% in recent days). It could be caused by “oxidation” Central electrode? And then from a minor family of strokes, produced by disintegrations, from the air to copper?

    Answers:
    As far as the oxidation of the electrodes decreases the conduction, does not affect the amplitude of the pulses, the reasons are as follows:

    1) The pulse current is so small that even a very high resistance (thick oxide) does not decrease the amplitude in measurable ways.

    2) As far as the electrodes oxidize, There is always some space between the oxidized points (microscopic perforations of the oxide) and these perforations, combined with the slight conductive layer that forms on all surfaces for effect of moisture, lead to still have a surface in electrical contact with the metal. Maybe it's contacts with high resistance, perhaps hundreds of mega ohm, but the only effect of this resistance will only slow the ascent of impulses. In the end, however, all offices will arrive where they arrive and you will not notice any decrease in amplitude of the pulses.

    3) We tested this by coating the Central pad with a sheet of paper. The paper "should" be an insulator but actually has a strength of tens of giga-ohm. And the result was to have exactly the same impulses of an electrode does not "block" with paper.

    Loss of sensation
    ———————————————————————————–
    Since you didn't have a strong moisture then we don't tell you what could have happened. We suggest anyway to inspect the TP1. If there are leaks (due to moisture or other) the tension on the TP1 salt and when it gets to 1.5 Volts and over the sensitivity decreases a lot and there are few pulses.

    Burst pulses
    ———————————————————————————–
    If you count pulses per burst check TP3 with oscilloscope. If it's 50 Hz then you must improve the shielding (brass double holes netting). If they are, then this may be caused by conducting random undulations moist air.

  2. William says:

    I wanted to update the situation with regard to the above comment posted in my name by Livy.
    After a review of the room made by him, with replacement of any faulty component, the sensitivity and stability of the room has reached very high levels.

    I implemented, taking advantage of the free channels, pressure sensors, temperature and humidity (Thanks to the good Alessio!!), in order to have a complete picture of changes in the conditions of measurement (any air movements that occurred during the measurement) that may change the data.

    I leave you with a chart “cool cool” made of very low concentration condition (environment with controlled mechanical ventilation).
    https://drive.google.com/file/d/0ByNPlNE2fCMqT1ZZeDZwTENxMkE/view?usp=sharing

  3. mario says:

    The realization of ionic room I am not clear what potential is connected the armor of the jar with lids.
    If it's a shielding, should I connect to “ground-earth” (ground/reference) or is it better to leave it floating ?
    I do not find this information on the designs and I would appreciate it if you could clarify this point.
    Thank you to all the team and congratulations on your excellent work.

    • Livio says:

      Should be connected to GND.
      The best spot is the negative of the connector where the three wires from the Master.

      If you leave the flying outside disturbances, coming from the electrical system, saturate the preamp and does not work anymore.

      On this page there are a lot of useful information:
      http://www.theremino.com/hardware/inputs/radioactivity-sensors

      • mario says:

        Thanks Livio for your answer.
        I would have a few more questions : How can you be sure that the measurements obtained with Ionic radiation actually depend on Radon Chamber ?
        If you are using a geiger, instead of the ion Chamber, It is possible that the count is in part due to the presence of Radon ?
        To conclude: isn't it true that alpha/beta and gamma radiation are all detectable using the concept of ionization ?

        Thanks for your great patience, Mario

        • Livio says:

          Beta and gamma ionize them too, but the number of molecules are ionized by any disintegration is about a hundred times less than those produced by Alpha disintegration.

          Also the disintegrations of Radon (and also of Thoron) have energy from 5 AI 7 Mega electron volts, versus just a few hundred KeV beta and gamma of products from almost all radioactive substances.

          Whereby the electrical impulses that develop after the FET are decently sized for Radon and Thoron but so small as to be absolutely not measurable for everything else.

          In any case a room count-ion as our beta and gamma does not see them just. To be sure we used very energetic samples of various substances and we never saw pulses produced by none other than radon.

          Radon decays and his sons are only alpha and Beta. These Betas are weak, only a few hundred KeV and (as far as detectable by a geiger) merge with the natural background not be measurable.

          Finally, geiger tubes have a sensitive volume small, Perhaps a thousand times less than a litre of our room at ions. So in an environment where we measure a disintegration of radon per minute, a gaiger would span one disintegration per thousand minutes (sixteen hours) and this count would be totally masked by the counts due to the environmental fund, a hundred times more frequent.

          • Anonymous says:

            Thanks again Livio and congratulations for your project. Group of enthusiasts.
            Personally I am extremely intrigued by the phenomenon of Radon and the radioactivity in General.
            Unfortunately I find that the realization of the ionization chamber and electronic forms is very laborious and provides a result of hobby flavor, but I think I'm now in final phase.
            Mario

            • Livio says:

              Of hobby there is only the cost of materials. When was compared with professional equipment (We do not make names for correctness) was found to be superior in everything. Mainly faster but especially usable comfortably. By connecting it to Geiger, you get a chart already significant in record time (half an hour), While other rooms “Professional” still chew into them and then, After many hours, a single number.

    • Pavel Rope says:

      The chamber outer wall needs to be connected directly to amplifier ground pin, or connected to ground with minimum 100uF capacitor. OR you have to connect the minus of the amplifier to some external ground by wire. So 3 setups are possible and working. Otherwise you will experience very high noise.

      In fact, there needs not to be any shileding of the chamber, you can use only a single wall can. I have tested that and I’m still using it in one of my devices. But in that case (if there is not GND on the chamber wall, but positive or negative high voltage), you have to increase the output HV capacitor to 100uF, otherwise the noise will be very high (it acts in this case also as a high pass filter, connecting the chamber wall noise to ground. With this capacitor value the additional induced noise is reduced to not detectable and a single non grounded can can be used, but it is very dangerous and also the startup time is longer… I would recommend that only in case you are encorporating the radon meter into some insulated housing box. Also a 100uF cap for that high voltage is quite expensive. On the other side it is much easier to DYI.

      As mentioned above, I have also tested a configuration with a single grounded can wall and central electrode injected with high voltage. It works well and it is obviously much safer. But the S/N Ratio achievable with this setup is little lower (less than 70%) and also a performance in high humidities is little worse. And, of course, because in this case the chamber is of one potential, a higher calibration factor must be determined, because the whole chamber surface is active (There is no loss of ion stream at both chamber ends, as in original version).

      Heh, my name was translated automatically from Provaz to “Rope”, when entering the answer :-)

      • Livio says:

        We do not use a 1 uF capacitor bur only about 33 nF that is not dangerous. Then to reduce the noise we use a 10 to 100 Mega ohm resistor and a HiVoltage generator with a double stabilized power supply.

        But your solution with the central electrode charged with high voltage can work very well. Now we have no time, but sooner or later we will test this configuration and publish a modified version. Thanks for your tips.

        • Pavel Rope says:

          It is possible, that this 10 to 100 Mega resistor will affect performance in high humidity environment (over 80%). It may cause lowering of the high voltage and thus a loss of sensivity. But it is safer, that is absolutely true.

  4. mario says:

    Livio, I run the first tests of the ion Chamber, However, while measuring the high voltage (up TP) about 500VDC and the amplifier with the correct biases, I can't get the impulses even after 30′ of waiting. I set what had seemed more correct (Ion Chamber sensor, etc) in the program, using HAL: PIN1 – Slot1 – counter mode on the master.
    The master flashes quickly, but I can't seem to get ever pulses. And’ possible to have a sample setup for the program IonChamber.exe be used for Radon ? Thank you.
    PS: given that the forms of the Ion Chamber (HV and AMP) are made with SMD components and thus are “high”, You cannot close the cover as indicated in the project. I had to add another cover as thickness, soldered to the other two, to create a gap. If there are cracks you must tap them with The adhesive tape or can remain without problems ?
    Thanks again, Mario

    • Livio says:

      Hello,
      If there are cracks, or not put properly grounded all screens, does not work anymore.

      If there are long strands in this case does not work.

      The room is delicate and should be mounted without “variations” compared to the draft.

      If you set the output Slot in geiger other than in hal then not working (try to knock them over, If the slots are in place should count)

      The hal you should set Counter and not CounterPU.

      If it doesn't work you can send her to Alessio will place.

  5. Anonymous says:

    It would be interesting to see how you got to use 2.15 CPS/Bq/l. as calibration factor.

    • Livio says:

      You can ask more precisely to Marco Catalano di Lacerc (OnLine certifications):
      http://www.theremino.com/contacts/about-us#marco

      For now I answer what I remember…
      1) The calibration factor was modified to adapt to gauges that matter even the disintegrations of the descendants of Radon. It wouldn't be fair but they are all so.
      2) The current factor is then 0.43 CPS/Bq/l.
      3) To get to this given Mark has prepared a special unit with pipes, fans and a source of Radon. Then it went to a laboratory to compare it with other secure meters. Can't remember the name but I think it was a laboratory of Arpa.

      If you need anything else just ask or email us at engineering@theremino.com

  6. Mario says:

    Livio, I made Theremino with the Ion Chamber for Radon, afterwards, being a big fan of electronics, I thought I'd connect the Ion Chamber to a coupon with LCD that I designed to count the CPM of the sensor. The microprocessor is a PIC16F876 that I programmed with MPLAB-X in XC8. The prototype works well and each pulse on a LED launches a disintegration and send a clicks per piezo buzzer.
    Now I would like to see not only the value CPM, but also the equivalent dose in uSv/h. Then I'll use even with a Geiger (SBM-20) already note the conversion constant.
    But for the Ionic room how do I convert CPM in uSv/h ? Thanks and good job. Mario

    • Livio says:

      The empirical formula can be obtained from ThereminoGeiger, But even more easily I advise you to predict a number K.

      And thou shalt: USV/h = CPM * K

      At the beginning set K = 1.000 and then the change by comparison with Geiger until similar readings.

      However without Geiger which averages over time and figure you'll get raw data and not very significant. It would be much better to use a Tablet with 8 inches by 49 Euro Windows 10 and Geiger. You would provide the power, the battery charger l lithium and CE approved, the touch screen, the sounds of clicks, the Wifi if you want to see it from a distance… Or, even better a Meegopad from 80 euros which is very small and only consumes 200 but to 5 Volts.

      All controllable from a distance with TeamViewer via Wifi and also via the Internet.

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