A better use for the axial field.

[MTd2]

If it is being shown impossible to get decent focus cte. axial field why not trying a variable one. Make it spike with 30-100gauss 500ns before pinch. Thoughts?

[zapkitty]

MTd2 wrote: If it is being shown impossible to get decent focus cte. axial field why not trying a variable one. Make it spike with 30-100gauss 500ns before pinch. Thoughts?

?
Did any news in particular bring this up?

[MTd2]

Not news on the websites. Getting a trillion neutrons per shot by adjusting the axial field, as it was be hoped to achieve according to the November updated, was not achieved until now, despite of the persistent attempts to do so…

[vansig]

“shown impossible”? not exactly.

Let’s play “battleship”, only I’ll hide what are the right variables to adjust.
http://en.wikipedia.org/wiki/Battleship_(game)

[MTd2]

5F?

[MTd2]

Seriously now, the only two parameters to play with are pressure and the intensity of the axial field. Going down didn’t work and it seems there is not much room to go up. I am not sure about the reasons, given that 35KV, with the 10 banks that are actually working now, would still allow pinch at significantly higher pressures. So, the only thing that remains is playing with is the axial field.

I think the reason it won’t work with the axial field being constant it is that the path of the filaments are not really radially straight, but slightly randomly bended. So, a constant field will not converge perfectly the filaments to the axis, so they will meat at the axis with slightly different angular momentum. Some of them will bounce a little, others will arrive and converge fast. In the end, the density of the plasmoid will be small.

So, my idea is to let the filaments converge as much as possible and then give a large magnetic pulse. The filaments will be closer to the target, so they will miss the each other less, and will have the required angular momentum.

[Lerner]

Vansig uses exactly the same analogy as I have in the lab—yes, right now Battleship is the current game. Contrary to what MTd2 is saying, we have really just begun to search the parameter space, because we only have had the repeatability we need since the end of December. The search is complicated by the phenomena of the pre-shock we ran into back six months ago, and the window to avoid this may be quite narrow. Our theory gives us guides, but since we have not yet fully understood the pre-shock, we need to do some careful experiments. Good science takes patience—something some fusion fans need to learn.

If you look at the patent we have, you can see that the only reason that a very small initial magnetic field can influence the very powerful ones in the pinch is because the axial field gets greatly amplified during the run-down and pinch. Introducing the field very late will eliminate this amplification, so will make the field’s effect insignificant.

[MTd2]

Lerner wrote: If you look at the patent we have, you can see that the only reason that a very small initial magnetic field can influence the very powerful ones in the pinch is because the axial field gets greatly amplified during the run-down and pinch. Introducing the field very late will eliminate this amplification, so will make the field’s effect insignificant.

I read the patent, this is why I said that it also might amplify the random axial asymmetries between the filaments. So, I suggested a stronger one, but not too late.

[MTd2]

BTW, I also thought about the preshock. Having a larger magnetic field would give a larger set of values to try and less interference from Earth’s magnetic field.

[Ivy Matt]

Lerner wrote: we … have had the repeatability we need since the end of December.

Now that is good news indeed. I hope you’ve seen the last of the mechanical difficulties.

[MTd2]

Wasn’t that achieved by the end of September?

http://lawrencevilleplasmaphysics.com/index.php?option=com_lyftenbloggie&view=entry&year=2010&month=10&day=06&id=17:reliable-firing-achieved&Itemid=90

[Ivy Matt]

Unfortunately, more recently they’d been having problems with exploding spark plugs or something like that.

See here, for example.

[MTd2]

So, the October news was partly the machine playing a red herring on the team…

[Aeronaut]

MTd2 wrote: So, the October news was partly the machine playing a red herring on the team…

You can also think of troubleshooting FoFu along the lines of troubleshooting a dead CRT-based TV set- only when you’ve located and repaired the HV power supply issue can you begin fixing anything that may be wrong with the picture (which breaks down into Hor and Vert deflection coil drivers), sound, or tuner. Said tuner can be a riot if it has a closed loop AFC contributing to picture and sound problems.

And this is simple compared to LPPX.

[MTd2]

I am not good with analogies… So, I’d like what was the difference between the misfiring of before and the more recent ones.

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