Remember on the old BBS my giving out the three great fusion histories as references? Well I have been reading again, at length.
In the superb technical history of the early work, "Project Sherwood", by A Bishop, a somewhat detailed discussion is given on neutrons as a diagnostic tool.
For those interested in a direct read, your reference pages are ppg 80-94. I will papaphrase liberally here for those either too lazy to read the work or those who can't locate this 1958 rarity.
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It seems that in searching out plasma diagnostics, one of the many tools considered was neutron emission.
"Certainily one of the most satisfying methods of plasma diagnostics would be the measurement of neutrons emitted from the thermonuclear reactions in the plasma itself." pg83
Bishop states that up to 100 million degrees kelvin the neutrons increase rapidly. He also notes that below 1 million degrees there are too few neutrons to measure.
Between these two limits, he notes, it was discovered that neutrons are a very sensitive method of measuring plasma temperatures.
"A word of caution is appropriate, however concerning the use of neutrons as a diagnostic tool. Care must be taken to ensure that the neutrons originate from fusion reactions within the plasma itself and not from other spurious processes of relatively little interest."
Bishop tells a tale of interest regarding the fast pinch program with Tuck's Los Alamos "Columbus I" linear discharge tube researches into "fast pinch".
In 1955 neutrons were detected in rather large numbers as huge pulses were unleashed into these systems. (On the order of 10e5 neutrons per pulse). The concern was whether the neutrons were thermonuclear or were produced by a relatively few deuterons accelerated unidirectionaly to high energies striking other deuterons lodged in the walls or electrodes of the device.
A very elaborate scheme and exhaustive series of experiments were performed at Los Alamos and UCRL Berkley to determine what the story was. It was conclusively determined by all labs, using sensitive and highly direction-sensitive neutron detector arrangments, that the neutrons were coming only from the plasma itself, and not the walls or electrodes.
Other experiments showed that neutrons produced with as little as 10kv applied to the devices, still emminated solely from within the plasma!
"Hope ran high that these neutrons were of true thermonuclear origin." pg 92
These hopes were placed in doubt with some key work done by S.A. Colgate. The neutron numbers seemed high based on a number of theoretical calculations. A study of the deuteron energies within the plasma showed that with only 20 kv applied across the tubes, 50 kev deuterons were unquestionably located within the plasma!!! Somehow the deuterons were being pushed to velocities greater than typically were obtainable by looking at the simple max voltage applied.
It is necessary to take a micro look here into the 1950's mindset of trying to heat all the gas in the device to thermal temperatures. They were always looking and working for a thermal machine with all of the plasma at fusion temperature. The maxwellian was holding them back.
It was discovered that the pinch and sausage instabilities of the high current generated magnetic fields were the source of the super energetic deuterons and the extra neutrons (these were still d-d fusion reactions, but only a small localized, axial, effect). They came to call these "false neutrons". What amazes me is that they dared to call these, "non-thermonuclear neutrons"!!!! I will quote directly.
"Since the plasma as a whole had not been raised to thermonuclear temperatures, the neutrons produced in the process were clearly of non-thermonuclear origin and were given the name of instability neutrons (or false neutrons)" pg 93.
It seems that they were fixated on heating the entire plasma so that classic ignition could occur. So they referred to real fusion neutrons as false neutrons only because they were outside of their calculation envelope and the gas within the device was not at a uniform temperature.
This is sort of turning the glove inside out. It looks the same both ways.
The part of the cake they didn't want to eat, they threw away and then complained of having no cake.
We are not in this situation (thankfully) with the fusor as we are working in velocity space and are not a thermal device in the sense that they were seeking to operate. We are also not pinching, as the currents in our continuous operation devices are in the milliamp range. We are also not pulsing in the kiloamp range either.
We are operating a simple inertially confined electrostatic collider-accelerator device and all the neutrons are fast d-d FUSION neutrons! 99.999999999 percent of our d2 is ice cold! Only the hot little core is the reaction zone. We know this and make no appologies for it. WE are doing fusion.
I will continue to report information of a historical nature regarding fusion in this forum as it comes to light.
Richard Hull
Created on Friday, January 05, 2001 10:09 AM EDT by Richard Hull