FAQ - About electronic noise in neutron detection

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Richard Hull
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FAQ - About electronic noise in neutron detection

Post by Richard Hull » Sun Apr 11, 2021 5:32 pm

Electronic based neutron detection can be done using many available detectors. The fusor can be an electronically powerful and noisy RFI and EMI device.
Almost all neutron detectors are secondary or "stepped" detection devices that produce very weak signals. Likewise, many are subject to detection of other forms of real radiations in addition to neutrons. it is incumbent on the part of the person claiming neutron detection to guard against both noise and other forms of radiation if they are to be taken seriously in their claims regarding neutron detection.

As the normal electronic detector puts out very weak electronic detection signals, it is wise to pre-amplify this signal using a high quality pre-amplifier attached without an "pickup" or antenna-like cabling directly to the detector!! This can often be accomplished with correct and suitable coupling connectors. In this manner any properly terminated cabling of normal length will transport a much stronger and, hopefully, easily discriminated detection signal into suitable remote windowing or level detect electronics to warrant solid detections. I attach an image of a typical example of this where a formal Princeton GammaTech preamp is so coupled to a 3He proportional neutron detector.

Regardless of how one cables an electronic neutron detector, all cabling must be kept short and well shielded and not snaked past any electronically noisy device.

While all low output detectors are subject to noise, some few are noted for particular issues with not only noise but just getting them to function properly in amateur hands. Among these are many of the well known Russian Corona tubes and even the Russian smaller 3He tubes. Another tough to set up neutron detection tube are the surplus boron lined tubes. Far more satisfactory, high efficiency detection scenarios involve larger proportional BF3 tubes and 3He tubes. Also good are correctly set up Bicron BC-720 scintillator systems although with poor efficiency by comparison. FAQ on this scintillator found at
viewtopic.php?f=31&t=13933

Regardless of what you final setup, be very cautious that you are not counting both noise, gammas, and neutrons. Amateurs in the field of neutron detection include degreed experimenters. I am reminded of the Pons and Fleishman cold fusion work. Here expert PhD men of world renown in electrochemistry did not employee equally expert people in neutron detection, but "went it alone" due to experimental secrecy to their ultimate embarrassment.

There are only two well used methods of noise-free detection that are foolproof which are regularly used with fusion and neutron detection.

1. The bubble dosimeter - This can be used, shielded from any UV light, and gives a neutron dose via counting bubbles following a fusion attempt to yield a real emission rate count of neutrons, using simple mathematics. However they have a limited life of typically 6 months as they are a chemical system. They are usually obtained from BTI of Canada and are very expensive at the amateur level, $300 plus.
2. Neutron activation - Various elemental metals like silver or rhodium are easily neutron activated in a "slow" or "thermal" neutron flux or field. Such exposure activates or makes radioactive these metals.
Immediately following the end of exposure, they may be removed and counts taken with a simple, inexpensive Geiger counter. Using the isotope's known exponential decay rates one may figure the neutron levels to which they have been exposed, using suitable mathematics. Unfortunately, first pass amateur efforts at fusion do not produce many neutrons to do suitable activation.

For electronic noise reduction, keep all cables very short and well terminated to eliminate reflections and external noise. Be sure of your electronic detector selected for the job. Pre-amplify at the detector, if possible. Level or window discriminate genuine neutron pulses from gamma or noise signals found in all fusor setups. Pulsed fusion is, in general,100% intense noise and .001% signal. As such, it is a poor and nearly impossible candidate for electronic neutron detection methods.

Richard Hull
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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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