Proportional or corona?

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Artem Artemov
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Proportional or corona?

Post by Artem Artemov »

I want to buy some СНМ18-1 tubes. These are corona discharge counters with 3He. Not to be confused with the СНМ18, they are proportional. I need a reliable counter. No need to measure the energy of the particles. I need xray tolerance. Which counter is better for our tasks? Proportional or corona? Can I spend the money on the СНМ18-1 )))

If I use 4-5 tubes, will it help to improve the accuracy of the neutron counter? The readings will need to be divided by 5, right? How best to place the tubes? In one place or 4 different places from the vacuum chamber?

I really like that this is a big and heavy tube))) Pressure 3He 4-4.6 atmospheres.



Specifications

4 column - voltage range, volts.
5 column - corona discharge voltage
6 column-own noise (background)
7 column - background corona discharge current, no more than mkA
8 and 9 column-dimensions and weight (mm, grams)
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Richard Hull
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Re: Proportional or corona?

Post by Richard Hull »

Proportional tubes are much more stable in operation and work more reliably at the amateur level. They do require a good preamplifier to function, though.
There is little to having multiple tubes as each would have to have a separate preamp.

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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Mark Rowley
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Re: Proportional or corona?

Post by Mark Rowley »

Beware of the Soviet 3He tubes. They are excellent for static neutron sources such as PoBe or AmBe. However, they are very susceptible to the electronic noise that’s naturally generated by a fusor. Additionally, I’ve found them not to be totally blind to xrays.

To be clear, this is my personal experience with the three I have worked with. Their failure in a fusor environment led me to the CHM11 and CHM14 which are operationally excellent and quite blind to xrays.

Unlike the CHM series 3He tubes, LND 3He tubes operate great in a fusor environment with no notable issues.

You may have better luck with the Soviet 3He tubes. If you do, you’ll probably have to go to extra lengths to prove they’re in fact blind to the HV noise and any X-ray influence.

Mark Rowley
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Richard Hull
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Re: Proportional or corona?

Post by Richard Hull »

Mark is the man with the experience. Older Reuter and Stokes, Texlex and US made 4 atm tubes are superb as well and totally immune to X-rays and gamma rays, by nature. All tubes, Russian and US made MUST have a follow on discriminator to set the pulse level sent on to the amp such that only the very large neutron detect pulses are passed on the the counter. Xrays and gamma pulse "fuzz" and "hair" at very low levels must never be counted or you will be deceived.

Mark, I believe, is noting that the Russian tubes noise and x-ray/gamma levels are much more significant than in the US produced tubes. Careful oscilloscope use of the preamp outputs should be viewed using a powerful source of gamma and x-rays to get a feel for such signal heights as compared to a neutron detection signal and very carefully discriminated out of the pulse train sent to the amplifier.

Carl Willis posted a fabulous video on U-tube related to this critical process. He used a good US 3He tube and made it look simple. check out his videos at....

viewtopic.php?f=31&t=6053


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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