New Netburner MOD5270 carrier board does it all!

[Vernon]

Put the signal path parts in the Trump Bomb Detector circuit board - and tested it. I put a potentiometer in to adjust the IRQ delay, I just epoxied it, and will add one on REV1 of the design. I figured a fixed resistor would be OK but it was a little off. The scope picture (top trace) shows a Cesium 137 662KEV Gamma pulse. It measures about 1.2V, the gain is 2, the sensitivity of the detector is 1V per MEV, and so that is about right. Also - such pulses are not present unless the CS-137 is near the detector.

The bottom trace shows the IRQ signal - this is not exactly adjusted yet and it will be shortened so that the IRQ (negative edge) occurs at the pulse peak. The IRQ will trigger the A/D measurement and that value will be stored. Next I have to put in the MOD5213, the level shifter, and the RS232 adapter. Then start programming.

In addition to background radiation I will put a bottle of the most recent rainwater next to the detector. There will be some counts from Fukushima - but detonation of a nuke or another meltdown will result in a measurable increase.

[Vernon]

https://www.youtube.com/watch?v=omMBgnpB63Q

Circuit board is complete and the MOD5213, RS-232, and other components have been installed. The IRQ function has been programmed and in the video it counts raw pulses above 500KEV over a one minute interval. Initially I count background radiation (51 counts) and then put the test source near the scintillator. That gets it to 36K (and it was not there for the full minute). Video above.

Attachments show the screen shot of the test. First is the background count - then the CS-137 source is placed near the scintillator at some point after the start of the second minute. The count is 36,319. After part of the third minute the source is removed. The count is 28005. Note that these figures would be higher if the source was left in place for a full minute. The fourth count is the return to background after the source is removed.

Tomorrow, if all goes well, I should be reading the A/D.

[Vernon]

Got the A/D running! Yeee! Haaah! This is a test with the CS-137 source - it runs about 50,000 CPM right next to the scintillator. I read the A/D for each photon. Next - I will get a statistical profile by dividing the A/D reading by 10. I already divide the raw A/D (4096) by two so this will give a range of 0 to 205. I will then record the counts over time for each value in an array. That will give a statistical profile for CS-137 using this scintillator and this gain. If Trump little fingers the big red button - I will know!

[Vernon]

Data on the screen shows the distribution of gamma energy as recorded over a one minute count. This is the peak at 662KEV on the graph. There is the occasional high energy background hit ~1.5MEV, value approx 192, (not SC-137) but the energy is concentrated around 54. Calibration will consist of making a run and noting the bin with the highest count. Values in bins from -4 to +4 will then be counted as CS137. I am not seeking any calibration here - just a pre-Trump historical baseline. And then any relative changes can be noted!

A basic gamma spectrometer with a MOD5213 !

[Vernon]

Test starting with background (raw CPM 59, CS 137 counts 26). Placed test source about 6" away and got results of raw CPM 627 CS 137 = 517. It be scintillating! The peak always comes out in the mid 50's so the gain is stable. The gain can drift with changes in PMT High Voltage, and that changes the peak, so this means it is all stable and smooth. Should just require a quick calibration every couple of weeks.

Next - I need to format the data for the MOD5270 - and then it will be on the internets!

[Vernon]

There is a high energy photon, one that drives it to about the A/D maximum and lasts about 400 microseconds on the scope that must be a cosmic ray. It's energy is huge - higher than anything else. Boron has an istope that does 1.4MEV but that would be 110 to 120 on my device. The big one comes in at 192 or 193 - and that is the Op Amp on the +5 rail (a voltage divider brings it down to 3.3V).

So I have a count for cosmic rays!

What the bottom picture is saying is that the raw count, all photons over 500 KEV, is 59 for minute 2. During that minute counts with an energy identifiable as CS-137 was 31. High energy cosmic zoomies from space that drive the op-amp to the rail was 8.

The top picture shows a test with the Cesium 137 source about 6" from the probe. The raw count is more than the sum of the previous background and the CS-137 because there are a few Compton scatterings and so on. But the CS-137 counts definitively reflect the quantity of that isotope. Note that the high energy cosmic count is not affected. A geiger counter, in contrast, just gives you a raw count - everything counts the same without amplitude differentiation. It either ionizes the tube or it doesn't.

[Vernon]

Now on line at www.pahrumpgeigercounter.com !

Waiting for the first hour to see if that data comes out OK. Then I will work on storage and display of data for the previous 8 hours.

[Vernon]

Pictures of the web display (made some revisions), the circuit board, and the Russian scintillator. The scintillator consists of an NaI(Tl) crystal optically coupled to a photomultiplier tube. The assembly contains a high voltage supply for the photomultiplier tube that operates from a 5V input. It also has a preamplifier scaled to 1v per MEV that produces a nominal 200us pulse width. I had this custom made - as it usually has a battery and is scaled for computer audio input. I designed the circuit board and had it made in China (I put the parts in here). I can strongly recommend Russian Nuclear scientists. The guy who built the scintillator is really smart (has a Phd), understands what you want, and gets it done. I also recommend getting your circuit boards done in China as they offer excellent quality at 10% of US cost.

Ready for Donald "Little Fingers" Trump to drop the Bomb! I will know!

I am going to do a calibration mode where if a minute has more than 300 CS137 counts it will send the A/D value that had the maximum counts - and may automatically adjust the window (still thinking about it). It has been really stable but you want to know if the HV or gain drifted.

[Vernon]

https://www.youtube.com/watch?v=LGuoOBHfdIA

Video above shows a calibration run on the scintillator. I widened the window by 2 and when I add up the energies in the "bins" I also now find the bin index holding the maximum value, the value that got the most counts, and send it over. It is not presented on line but is dumped out the other serial port in the MOD5270. The anticipated center set in the software is 51. In this case after 3 or 4 minutes of warm up the evaluated center was 51 to 52. No change required! Awesome! Great for counting CS-137 and detecting nuclear bombs and meltdowns. If the high voltage in the scintillator or the gain drifted this peak would move and need to be reset. Ergo calibration about once a week.

Note that the CS-137 count in the movie was about 800 CPM. The picture shows a minute after the source was placed back in its shield at the other end of the room - only 2 counts.

The worlds only Netburner MOD5213 nuclear bomb detector!

[Vernon]

For my next upgrade, since the scintillator is working so well, I am going to do a MOD 5213 board that will run both the SBM-20 Geiger tube and the scintillator at the same time. The Geiger counter gives a commonly acceptable dose rate and the scintillator would miss high levels of radiation below 500 KEV. So the solution is to have both. I used a 68HS12 from Technological Arts (I program it in assembler) in the Geiger counter and other projects but the MOD 5213 is cheaper, faster, and has a higher resolution A/D. This board will essentially adapt the existing Geiger circuit that has worked so well for 6 years on line. PWM is applied to a 74HC14 that drives an IRL 510 Mosfet in an inverter circuit. The inverter transformer (I have several) is a surplus part from an out of production flash camera. Link below if you want one.

http://www.goldmine-elec-products.com/p ... ber=G13599

This circuit produces 400V for the SBM-20 tube. Feedback is supplied to the A/D from a voltage divider to provide regulation. Counts are coupled by the 100 pf 2KV capacitor and drive the 'HC14. This output will go through the level shifter to IRQ4 where it will be counted just like the scintillator pulses. I might also make a hand held instrument using both probes. The Geiger tube is about $20 on Ebay and the scintillator is $399 from Russia. You will be able to pay your money, take your choice, or have both. I will add a 4x20 display as I did with the MOD 5270.

Russian manufacturer email available on request.