FAQ - With fixed voltage, current and pressure, fusion varies!

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Richard Hull
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FAQ - With fixed voltage, current and pressure, fusion varies!

Post by Richard Hull »

This is a FAQ that might generate some discussion but is based on my own operational observations of late. This relates only to the more large volume, wire gridded, spherical fusors of which mine may be the only one in current operation.

Jon Rosenstiel sent me a PMT with Hornyak button to search for hot spots of my spherical fusor. I have yet to use it. The report long ago by the Washington State Consortium about anisotropy on their spherical fusor was well taken. Recently beam on target fusion and forward emission of most neutrons in such an environment have come to the fore. A three wire hoop fusor has six beams that impact the shell where preferential forward neutron emission might be found to increase the neutron count at those points. I have verified this to my satisfaction via measurements recently made by me on my working fusor. I speak to this in the FAQ in this forum on Volumetric TIER calibration of neutron detection analysis.

viewtopic.php?f=31&t=14303

In the use of a much smaller moderator on the Eberline PNC-1 that I have which uses a very small BF3 tube, I noticed that at a fixed voltage, pressure and current the analog meter can drift up and down over a +/-25% range in less than 1 minute.....Example: I was operating at the 35,000 cpm rate on my fusor using my huge 3He system. The small 3-inch by 3-inch by 6-inch moderator of the PNC-1 was placed almost touching my fusor. the PNC-1 analog meter was hovering rather widely around 400 cpm! Over one minute at a fixed operating point the meter moved over a rang of 330cpm to 500 cpm! but would drift through the 400 cpm point more or less as a midpoint.

I quickly with the stable operating point counted four one minute digital counts with my 3He system and got 35,453 - 34850 - 35932 - 33856. Realizing that any count over 10,000 over a fixed period, one minute in this case, would be at about 4 sigma significance, I was forced to a realization. The giant volume of the 6-inch spherical fusor had a variable fusion rate based on its many neutron producing modalities even with a fixed voltage and current input and fixed pressure!

I would never have expected this were it not for the crazy variability of the analog system. I assume the variability of a much greater percentage on the PNC-1 is due to the smaller intercept of the moderator being more sensitive to variations measured over a smaller volume right at the large volume neutron generational source.

I am led to the conclusion that fusion is and will never be a constant based on fixed and constant voltage, current and pressure conditions within the simple, large gas volume of a wire gridded spherical fusor!
There are far too many modalities with all not in play to equal degrees due to multiple random fusion events throughout the device. I would be very interested in any such measurements taken with different reactor geometries.

Richard Hull
Attachments
PNC1 fusor Vanno.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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Richard Hull
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Re: FAQ - With fixed voltage, current and pressure, fusion varies!

Post by Richard Hull »

Alas, what a tedium!...I am going to point out the variability as noted above by combining proof positive postings from some image du jour runaway, off topic postings.

Background

A new "super neutron counter" appeared on E-bay. There were about 14 identical Ludlum neutron counters in all. It seems all 14 were instantly gobbled up by fusioneers here on fusor.net. WOW! They proved to be super high dollar, high end, high performing units with amazing capabilities. One capability was the dose rates taken at user chosen intervals of .5 sec or more. It turns out this occurred just at the time of this FAQ's posting and my noticing this variability on my Analog BF3 neutron counting systems.

Matt Gibson was wise and, yet, confused as he used his shiny new Ludlum to check for his introduction to the neutron club while running his fusor. He posted one of his micro time interval "dose rate" graphs that the new Ludlum recorded. Questioning his results. I saw immediately that this was a far more revealing nature of the fusor doing fusion, and also stupidly posted a reply to his report in the images forum.

Please read below and study the PDF graph which Matt supplied of his result in doing fusion and the dose rate average as compared to my reply with my, same day fusor run, results. It is important to note how close our operational conditions and parameters were that matched, closely, both of our results. Stunning!

The pertinent posts

First, please read Matt's post. Then, view his "best run" data graph (See his attached PDF graph below). Note his confusion regarding his results.

***********************************************************************************************************
Matt Wrote............
Update:

Some more playing around. This time, I hit over 8mR/Hr (Ludlum value) a few times. This occurred at 40kV@7mA and 15.2 microns. In order to achieve this combo, I have to have my system running at full tilt (Deuterium flowing at 10sccm and chamber valve full open with the turbo going at 100%).

Here is a graph of the raw data from the Ludlum. X-axis is time in 1/2 seconds and Y-axis is mR/Hr from the Ludlum. You can see me adjusting/fidgeting with the Deuterium flow and the chamber valve. As I crank up the Deuterium, the mR/Hr drops and then gradually climbs again. The large drop in mR/Hr occurred when I just decided to go for broke and janked it up to 10sccm (Max flow). Run time was a little over 16 mins. At this point, the Ludlum is sounding irate…If not neutrons, what could all of this be?

I have some HDPE coming...Hopefully I'll be able to active some silver and then call this a success?

*********************************************************************************************************

Next is my reply and comparison with comments related to my original posting in this FAQ.

********************************************************************************************************

I hope this is not comparing apples and oranges. I run a sphere. I am back in the biz to compare various methods of measuring and I am happy to say that within 10% or more they all agree. I post here as the conditions are similar in some ways to Matt's work with a totally different measuring scheme. I was amazed at the close similarities of our results, considering the difference in devices and methods of measurement.
Will add a modified reply relating Matt's reply above and my own here to my FAQ on the variability of fusion rate in a fusor.

I now have my Rem ball and my PNC-1 working along with my normal 3He detector.

Last night's run topped out at a bit over 500k n/s based on the 3He calibration. I activated Rhodium to 22 times background (background here is about 4 times most folks GM background) both the mrem/hr reading of the Rem ball and the PNC-1 block moderators were varying over 10 second intervals, up and down as noted in other recent postings by me. This matched Matt's wild second based insane variations and his more moderate time averaged variations. My analog variations, (real time needle swings), were on the order of his moderated average variations in mrem/hr.

My Data: 41kv, 11ma, 10microns D2,....At this operating point PNC-1: 6.8 - 7.4 mrem/hr.....Rem ball/PNR-4 lin-log reading: 6.6 - 7.8 mrem/hr....Both the ball and the PNC-1 block moderators jammed against the fusor. 3He count was 86,205 cpm (translates to over 517,000 n/s TIER).... Rhodium peak activation was ~1300cpm (rhodium's very small surface area foil exposed 2pi to GM tube = ~6 sq cm).

1. I have to believe Matt is doing fusion and that his posted reduction above proves my point that all fusors are not steady fusing entities, but have on the micro time scale, immense fusion output differentials. (Matt's and other's data)....New Ludlum micro dose delivery detectors.
2. However, when analog averaged over10-20 seconds, a net emission of fusion neutrons swings about a common point +/-10%.....(Remball/PNC-1)
3. One full minute hard digital counts can vary about +/-2%.... (3He).
Activation over time and bubble dosimeters would be the pure net emission or dose total indicator.

As noted before and stated in my FAQ....

The fusor due to its simplicity with many modalities with cross interference between them is not a steady fusioning system on extremely small time scales but over a number of minutes can be reduced to a reliable net dose device if all of the parameters in its operation are held steady. Even a morass of confused emission with steady parameters feeding it will , by statistical analysis over time, settle into a usable average emission rate and TIER, in our case.

Note: all of this valuable neutron radiation data on this new Ludlum system should never appear in images du jour or in the construction forums. It belongs in the neutron and radiation forum... Oh well, we do let such things smoothly flow from one thing to another, quite innocently I might add. I hope all this good stuff related to neutron counting and measurement is not lost in future buried hopelessly in the images forum here. It is for this reason that I will edit this into the neutron variability FAQ post as a reply...

Richard Hull
Attachments
Best_Run Matt Gibson.pdf
(182.33 KiB) Downloaded 274 times
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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