Steps between a moderated BF3 tube to a readable, usable output

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Luca Aldridge
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Steps between a moderated BF3 tube to a readable, usable output

Post by Luca Aldridge »

Hi
I’ve looked at the FAQs and can’t seem to find much detailing the process between the detector tube and the final output.

Let’s say that I have bought a new BF3 tube rated at 1700V and the PSU for it.
How do I go about connecting it to whatever is needed to get a readable output, and in addition, what are those things that I need?

Any questions and I’ll be happy to clarify.
Luca Aldridge
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Joe Gayo
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Joe Gayo »

https://www.youtube.com/watch?v=skP3SWWR9Kw

BF3 ---> Charge Sensitive Amp (109PC Ortec, 175 Tennelec, etc.)
HV power supply (make sure this is never plugged into the CSA "hot" since this can destroy the front end JFET, always ramp the voltage slowly ~10seconds)
Shaping Amplifier (2022 Canberra)
Note: Both the HVPS and Amp connect to the CSA
Single Channel Analyzer (550 Ortec) connected to Amp
Timer/Counter (Arduino) connected to SCA
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Dennis P Brown
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Dennis P Brown »

Joe a really great link that covers all aspects extremely well. That really sums up the details. Maybe don't use so many abbreviations since many new people don't know what they mean and could use the full word(s). I generally give an abbreviation in parenthesis right after first time using the full technical word.

Besides this method, one can buy complete 'singular' system like an Eberline or other units with a built in pre-amp, power supply and discriminator circuit that is mostly 'turn-key'; that is, just connect such a unit with a cable to the detector or the unit already has the appropriate detector. However, such units are generally not as versatile as the system shown but are more available; however, that vid really explains and sums up all the details in what needs to be done to get a properly discriminated neutron signal from a mixed signal source.
Luca Aldridge
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Luca Aldridge »

I’ve watched the video and read the reply, and after some preliminary research it seems that the parts are all approximately £500 each from various sources (PSU being more and Arduino, I already own)

I’m interested in the “Eberline” I believe you said - a wider availability is favourable for me as I’m in the UK and most of the market seems to be in the US. From what I can see it’s a moderator ball with a BF3 tube in it and doesn’t seem to have any other equipment attached to it (see link)
https://www.thermofisher.com/order/catalog/product/NRD9
Isn’t that back to square one, if you willl, in terms of adding all the preamp and other equipment?
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Liam David
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Liam David »

You can probably get away with using a Ludlum Model 12 or other >=1500V, adjustable discriminator Ludlum. I use a model 12 and 3He tube with a custom pulse output for digital counting. It's rock solid--completely insensitive to noise, even during large arc events that kill everything else in the vicinity. Mark Rowley describes a BF3 / model 3 setup here: viewtopic.php?t=13216
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Richard Hull
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Richard Hull »

Yes, NIM gear is often a bridge too far for the average arrival here. Still it is hard to beat any of the old Carl Willis videos for simplicity of concept and completeness Now that Carl is not here on a regular basis anymore it is tough to beat Mark Rowley for similar clear and concise video expositions.

Most arrivals have no extensive electronic skills. This is sad, of course as all the gear needed to do the BF3 to counter route is relatively easy for the electronics experimenter of some merit to avoid all that NIM gear.

Richard Hester, electronic designer guru, long ago supplied a great all in one circuit that contained everything on one board. Richard! If you are out there can you repost?

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Joe Gayo
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Joe Gayo »

Having worked on many CSA designs, including improving Richard's, I've settled on the following schematic. I use it extensively. The opamp is LT1007.
~1400mV/pC, 35 electrons RMS noise
The gate of the main JFET is on a "diving board" so that the leakage is minimized.
CSA.PNG
PXL_20220313_181345535.jpg
PXL_20220313_181327743.jpg
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Jim Kovalchick
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Jim Kovalchick »

I often connect my proportion tubes to a Ludlum model 2200. It's an all-in-one hv supply, single channel analyzer, rate meter, and scaler. They can get pricey even used, but with patience, they can be found on ebay at a good price.
The cost beats buying multiple nim modules.

Because amplification doesn't happen until the unit, it's best to keep the cable relatively short.
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Joe Gayo
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Joe Gayo »

"All-in-ones", meters, etc. provide a black box that is hard to troubleshoot. The real advantage of NIMs is that they are modular and monitoring signals is straightforward with an o-scope. Of course, their modular nature makes them flexible when you want to change detectors or compare two detectors, etc. I think you could put a NIM system together for under $500.

Quick Ebay Search -
TENNELEC TC 246 - AMP/SCA - $86
TENNELEC TC 945 - HVPS - $79
ORTEC 773 - Timer/Counter - $50
ORTEC - Crate - $150

TOTAL: $365

I think you could beat this. Many lots of NIMs come up and with "Best Offer" it could be much lower. Last month a saw a fully stocked crate with everything needed for $250 with free shipping.
Last edited by Joe Gayo on Sun Mar 13, 2022 3:20 pm, edited 1 time in total.
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Richard Hull
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Richard Hull »

Thanks Joe. The preamp is always the stumbling block for the proportional tube neutron detection electronics. It is the most important of all the circuitry. It must be mounted in a fully enclosed metal shield box. Joe's circuit uses +/- 9 volt batteries in the box. This is the best possible situation as outside noisy power supply lines are obviated. There is the issue, outside of this box of biasing your tube with high voltage. This can be a simple circuit either inside or outside of this preamp box. Typically, this is done inside the preamp box by manufacturers.

I supply one that is used by Princeton Gamma Tech

Note the output to capacitor coupled preamp would go to Joe's circuit input. As always, bring up the bias voltage slowly. FET's do not like snap on-snap off 3kv spikes fed into their gates.

Richard Hull
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3He bias input.jpg
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
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Joe Gayo
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Joe Gayo »

Biasing is important. I made it external since I wanted the flexibility to change the bias resistor and filter options, but it could be integrated easily.

I tend to use a 2nd or 3rd order filter instead of 1st in Richard's Gamma Tech schematic.
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Dennis P Brown
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Dennis P Brown »

For people such as myself, what is 2nd or 3rd order filtering? A schematic and explanation would be something that I'd think would clarify that subject.
Luca Aldridge
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Luca Aldridge »

Thanks for all of these replies, they will be invaluable to me.
I’m erring to the side of the all in one systems - perhaps the Ludlum model 2200, as Jim said, or something like this:
https://www.mirion.com/products/nim-201 ... te-monitor
Although I expect it will be pricey it seems like what I need

I’ll also consider building my own circuit but the extent of my skills are a few hours of experience soldering

Unfortunately I don’t think the route of buying my own amps and modules will work.

Thanks again for everyone’s help

As a side note, it might be worth adding this the the FAQ list as it has a lot of concentrated information about detection with BF3 tubes
Just a thought
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Dennis P Brown
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Dennis P Brown »

I would think that NIM units at $500 each would be a cheap system compared to that neutron detector system you linked.
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Dennis P Brown
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Dennis P Brown »

The Ludlum model 2200 is a good unit but will not, without the proper detector tube (say a 3 He), detect neutrons.
Luca Aldridge
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Luca Aldridge »

How easy is it to connect it all up, and also to make sure that I'm not doing something wrong? Bearing in mind that the forums can offer lots of advice

Looking at this video
https://www.youtube.com/watch?v=skP3SWWR9Kw
the system seems fairly simple, but how long did it take Carl to build and source that?

Will the items be approx $500 each or far less, like in Joe's comment (Quick Ebay Search -
TENNELEC TC 246 - AMP/SCA - $86
TENNELEC TC 945 - HVPS - $79
ORTEC 773 - Timer/Counter - $50
ORTEC - Crate - $150
TOTAL: $365)

Your point is a good one, and I could use the money saved on better components elsewhere in the fusor.
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Dennis P Brown
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Dennis P Brown »

Those NIM units still require a neutron detector tube - say a BF3 or 3He (as well as proper high voltage cable.)
Luca Aldridge
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Luca Aldridge »

Yes - I also need to find one of those from somewhere

The HV cabling, I would use some left over from connecting my HVPS to the fusor itself.
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Dennis P Brown
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Dennis P Brown »

You will need high voltage coaxial cable (shielded) - not high voltage power cable. China sells good HV coaxial cables at very low prices - I just ordered some. Get connectors types that match your detector units - there are a number of types depending on your equipment.
Luca Aldridge
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Luca Aldridge »

I'll do that.
I was under the impression that shipping from china is extortionately expensive - When I was buying lead screws etc the shipping was in excess of $50 for each item. Perhaps this problem minimises at low weight items?
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Dennis P Brown
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Dennis P Brown »

Sorry but the difference is in the country; here in the US Chinese goods are shipped here so often that import fee's are tiny (for most products.) I understand Europe can be expensive.
Luca Aldridge
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Luca Aldridge »

Ah that makes sense.
That’s annoying.
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Richard Hull
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Re: Steps between a moderated BF3 tube to a readable, usable output

Post by Richard Hull »

NIM can still be had somewhat inexpensively off E-bay. It is a flexible system that once assembled can be used in many different future configurations. It is very dated, that is true and only the most modern modules have any integrated circuits in them. I have already ripped the guts out of a couple of modules and rebuilt them to TTL, 5 volt signal standards, using far less power. I will also, in future, start putting an Arduino Nano in a module or two.

In the above manner, I can retain all the value of the NIM module concept. It is a nuke guy's erector set (mechano for the euro folks)

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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