I am interested in the general question of sphericity of the BFR MaGrid.
If I were to build (or have built) a series of lower power MaGrids, each with an expected improvement in spericity or confinement efficiency, how would I go about measuring that?
A true half scale WB6 would be about 15cm diameter and would have about 50 turns of wire (or 200 turns of half diameter wire). I want to simplefy. I am thinking maybe 16 turns. And with the lower magnet power I think a lower drive voltage; so the sheath can be less perfectly smooth and polished.
The parametric series I am considering goes something like this.
6 toroidal magnets, OD=15 cm, 16 turns. "Nub" connected (WB6ish baseline)
6 "square" magnets, OD=15 cm, 16 turns. "Nub" connected (Bussard's WB7ish - better efficiency, shorter line-like cusps)
6+8 square+triangular, OD=15, 8 turns each, side connected (no nubs, better efficiency - less loss from unprotected metal?)
6+8 BOWED s+t, OD=15, 8 turns each, side connected. (better sphericity?)
So how would I measure improvements in efficiency and sphericity?
Oh, and I want to run this steady state so the filed and voltage would be even lower still.
An Experiment into Sphericity
Measure the magnetic field in air.
Get the device operating. Turn it off. Measure the integrated decay pulse of ions.
Do the same for both devices. Better confinement should lead to more stuff confined.
Or you could measure neutron fluxes with D-D. After doing a background measurement. Shielding the detector and detector placement is important.
Also control of grid voltages to .01% at very low ripple. High ripple supplies are useless for making real measurements in low neutron production regimes unless you can correlate neutron detection with supply voltage to 15 or 16 bits and 50 nS or less. If you just want to make a couple of neutrons to join the Neutron Kids club - well that is different. That says that you need electronic current limits not the usual series resistor. Although for initial start up testing of the device a resistor is fine.
The same goes for coil current supply. Regulate, regulate, regulate. Filter, filter, filter.
Then of course you will want to do POPS.
Get the device operating. Turn it off. Measure the integrated decay pulse of ions.
Do the same for both devices. Better confinement should lead to more stuff confined.
Or you could measure neutron fluxes with D-D. After doing a background measurement. Shielding the detector and detector placement is important.
Also control of grid voltages to .01% at very low ripple. High ripple supplies are useless for making real measurements in low neutron production regimes unless you can correlate neutron detection with supply voltage to 15 or 16 bits and 50 nS or less. If you just want to make a couple of neutrons to join the Neutron Kids club - well that is different. That says that you need electronic current limits not the usual series resistor. Although for initial start up testing of the device a resistor is fine.
The same goes for coil current supply. Regulate, regulate, regulate. Filter, filter, filter.
Then of course you will want to do POPS.
Engineering is the art of making what you want from what you can get at a profit.
Thanks for the comments. I will have to think on them for a bit.
Regarding measuring the magnetic field in air, such data would be good to know. However, I think what I am trying to determine is the sphericity (focusing power) of the potential well which is generated by electrons flowing into, around in (a LOT) and out and in and... I am not sure how I would do that in air.
Also, given the lower voltage and B, I am pretty sure I won't be getting fusion, so neutron detection is very low probability. Remember, I want to run this thing not only 1/2 size, but 16/50th scaled turns and steady state as well so the amps would go way down. Thus I am expect a much lower B field and suspect the MaGrid voltage would thus be WAY too low for fusion. Am I wrong?
But if I run this thing in diagnostic mode with a fair density of gas, there will be losses to the neutral gas that might mess up the real worry which is loss to the MaGrid or chamber wall. I think I will need a LOT of guidance on how to seperate the loss to neutrals from the loss to other stuff.
In the end, I am currently envisioning some way to detect the well sphericity by glow intensity of the diagnostic gas. Also, I hope to determine the non-gas electron loss thru steady state current thru the MaGrid and wall. This may not work at all.
Other suggestions anyone?
Regarding measuring the magnetic field in air, such data would be good to know. However, I think what I am trying to determine is the sphericity (focusing power) of the potential well which is generated by electrons flowing into, around in (a LOT) and out and in and... I am not sure how I would do that in air.
Also, given the lower voltage and B, I am pretty sure I won't be getting fusion, so neutron detection is very low probability. Remember, I want to run this thing not only 1/2 size, but 16/50th scaled turns and steady state as well so the amps would go way down. Thus I am expect a much lower B field and suspect the MaGrid voltage would thus be WAY too low for fusion. Am I wrong?
But if I run this thing in diagnostic mode with a fair density of gas, there will be losses to the neutral gas that might mess up the real worry which is loss to the MaGrid or chamber wall. I think I will need a LOT of guidance on how to seperate the loss to neutrals from the loss to other stuff.
In the end, I am currently envisioning some way to detect the well sphericity by glow intensity of the diagnostic gas. Also, I hope to determine the non-gas electron loss thru steady state current thru the MaGrid and wall. This may not work at all.
Other suggestions anyone?
A Hall effect probe should do the job if all you want to do is detect the shape of the magnetic fields. A lead screw/stepper motor set up should help. Make sure the probe is non magnetic.KitemanSA wrote:Thanks for the comments. I will have to think on them for a bit.
Regarding measuring the magnetic field in air, such data would be good to know. However, I think what I am trying to determine is the sphericity (focusing power) of the potential well which is generated by electrons flowing into, around in (a LOT) and out and in and... I am not sure how I would do that in air.
Also, given the lower voltage and B, I am pretty sure I won't be getting fusion, so neutron detection is very low probability. Remember, I want to run this thing not only 1/2 size, but 16/50th scaled turns and steady state as well so the amps would go way down. Thus I am expect a much lower B field and suspect the MaGrid voltage would thus be WAY too low for fusion. Am I wrong?
But if I run this thing in diagnostic mode with a fair density of gas, there will be losses to the neutral gas that might mess up the real worry which is loss to the MaGrid or chamber wall. I think I will need a LOT of guidance on how to seperate the loss to neutrals from the loss to other stuff.
In the end, I am currently envisioning some way to detect the well sphericity by glow intensity of the diagnostic gas. Also, I hope to determine the non-gas electron loss thru steady state current thru the MaGrid and wall. This may not work at all.
Other suggestions anyone?
And dial gauges. Lots of measurements and data reduction.
OTOH an Argon plasma (nice emissions in the visible) might be good. Or sodium vapor. plus a narrow band filter to eliminate (as much as possible) thermal radiation. Or maybe Neon. Or some other noble gas.
Helium looks good. Not too many lines and a bright one in the yellow.
http://chemistry.bd.psu.edu/jircitano/periodic4.html
Engineering is the art of making what you want from what you can get at a profit.