Ion injection question?

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mattman
Posts: 459
Joined: Tue May 27, 2008 11:14 pm

Ion injection question?

Post by mattman »

Hello,

1. If the gas is puffed in, then the ions are formed in the center, through collision with electrons at ~12,500 eV, then the ions are already in the center. How do ions then "fly in" at 10,000 eV to hit and fuse?


2. If the ions are formed outside the center, at the gun, how are they injected? There is a 12,500 voltage drop to attract the electrons towards the rings. This is an uphill battle for any ion. There is a 10,000 volt negative cloud attracting the ion, but that still leaves a 2,500 hill the ion needs to overcome. You can inject at over 2,500 eV - there is probably some tuning here - but doing that means you will need to make a gap in the 12,500 volt downhill for the electrons.


???

happyjack27
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Re: Ion injection question?

Post by happyjack27 »

mattman wrote:Hello,

1. If the gas is puffed in, then the ions are formed in the center, through collision with electrons at ~12,500 eV, then the ions are already in the center. How do ions then "fly in" at 10,000 eV to hit and fuse?
this is a blessing and a curse of gas puff injection - theoretically the protons will never leave a closed boundary - the maximum puff size, so to speak. this is a blessing because hey, that's called confinement. it's a curse, because a lot of those protons are going to find their zero-inertia point at a fairly low potential energy, so yeah, they're not going to have high KE in the center. on the flip side, they will contribute to the density more.

gas puff injection though is a bit of a god-send, as it completely bypasses any electromagnetic issues with injecting charged particles in from the outside. it's largely thought of as the ideal injection method for larger machines, which don't require as much timing precision.

2. If the ions are formed outside the center, at the gun, how are they injected? There is a 12,500 voltage drop to attract the electrons towards the rings. This is an uphill battle for any ion. There is a 10,000 volt negative cloud attracting the ion, but that still leaves a 2,500 hill the ion needs to overcome. You can inject at over 2,500 eV - there is probably some tuning here - but doing that means you will need to make a gap in the 12,500 volt downhill for the electrons.

???
the fusion takes place in the center, not on the rings.

it's a two-step process:

1) the electrons are held in the center by the magnetic fields.

2) the ions are attracted to the center by the electrons.

it's done this way because ions are on the order of 1,000 times as heavy as electrons, so they take on the order of 1,000 times as much force to accelerate, and since magnetic field strength (the lorentz force) is a function of _velocity_ rather than inertia, and at the same inertia the electrons are going 1,000 times faster than the ions, so that's 1,000 times the lorentz force, and f=ma, so a unit of force accelerates an electron 1,000 times more than a proton, multiply the two together and you see that a magnetic field effects an electron 1,000,000 times as much as a proton!

so the magnetic fields confine the electrons a million times better than they do protons. so the whole machine is designed to confine ELECTRONS rather of protons.

but you say, "well that's quite pointless, electrons don't create fusion at all". no they don't but they, attract protons better than anything else in the universe!

so the coils confine the electrons electro-magnetically, which in turn confine the protons electro-staticly. a rather elegant solution, me thinks.

EDIT:

--oh the electrons actually travel uphill. they're pushed that way by the magnetic field which twists and turns them back around. once inside the magrid the protons have a downhill path. outside the magrid, not so much. i presume ion injectors are theoretically on cusps at an electrostatic inflection point, or a little outside and shot w/KE at least high enough to reach the inflection point.

mattman
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Joined: Tue May 27, 2008 11:14 pm

Post by mattman »

Ok,

An ion cannot make it to the rings if it is being pushed by 2,500 volts in the opposite direction. This leaves 2 options:


1. Put the ion source right next to the rings. This is hurts recirculation, that's bad. But, it starts the ion at the top of the 10,000 eV "hill" it needs to fall down to fuse.


2. Puff the D2 in before it has any charge. This forms the ions inside the rings. That’s what Bussard did. This means that the ion has formed at the bottom of the "hill". It is hard to see how it can now get to the 10,000 eV needed to fuse. It somehow needs to get back up to the top of the hill to fall down it again to hit and fuse.


The Iran simulations seemed to encounter this issue - their ion sources are placed inside the rings. Here are two thoughts on this:


A. Anyone know if Bussard heated the D2 before puffing it in? (Tom?)


B. What happy jack said: the magnetic field has different effects on the electron & ion; this might give some wiggle room. I need to think about this. To quantify these effects we need: the magnetic moments of D2, a free electron and a D2 ion. We also need the masses and volumes of these objects.

mattman
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Joined: Tue May 27, 2008 11:14 pm

Post by mattman »

We need to make 6 plots. Across the 67" diagonal in WB6, we need to estimate:


1. Electric field strength for D2.

2. Electric field strength for the D2 Ion.

3. Electric field strength for the electron.

4. Magnetic field strength for D2.

5. Magnetic field strength for the D2 Ion.

6. Magnetic field strength for the electron.

ladajo
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Post by ladajo »

In full scale machines, Bussard liked the idea on neutral stripping to provide fuel. It also provides a nice source of e-. To the point that he thought that there could be enough e- that you would not need to inject. Nebel also thinks the same things.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

KitemanSA
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Location: OlyPen WA

Post by KitemanSA »

mattman wrote: 2. Puff the D2 in before it has any charge. This forms the ions inside the rings. That’s what Bussard did. This means that the ion has formed at the bottom of the "hill". It is hard to see how it can now get to the 10,000 eV needed to fuse. It somehow needs to get back up to the top of the hill to fall down it again to hit.
No, gas puffed in at the ring get's ionized at the EDGE of the well and has the entire well depth to fall into. What is the issue?

happyjack27
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Joined: Wed Jul 14, 2010 5:27 pm

Post by happyjack27 »

yes, that is an ion injection question.

hanelyp
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Post by hanelyp »

ladajo wrote:In full scale machines, Bussard liked the idea on neutral stripping to provide fuel. It also provides a nice source of e-. To the point that he thought that there could be enough e- that you would not need to inject. Nebel also thinks the same things.
If neutral stripping provides all the electrons needed after initial startup, you still need to heat the electrons. If annealing of electrons works well enough, microwaves might do this. Even better if the microwave frequency could be matched to a suitable harmonic of nominal time for electrons to cross the wiffleball.

ladajo
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Post by ladajo »

A modified ECR approach.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

mattman
Posts: 459
Joined: Tue May 27, 2008 11:14 pm

Post by mattman »

We're good.

Ionization happens when the D2 first reachs the rings.

There, the electrons occupy a high density magnetic field.

That means those electrons have a high potential energy.

That means they have a low Kinetic energy.

But, if they have an energy higher than 16 eV, the D2 should be ionized.

The ion is now forming at the top of the "hill".

It flyes down, towards the center, hits another ion and fuses.


The next question is where is the best place to put those emitters...

KitemanSA
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Location: OlyPen WA

Post by KitemanSA »

mattman wrote: That means those electrons have a high potential energy.

That means they have a low Kinetic energy.
You have that backwards. At the edge of the well, the electrons have high kinetic, low potential.

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