Net energy question

[gblaze42]

If Bussard can achieve a model that produces net energy, how does he plan on extracting that energy? As most fusion work has been to confine and isolate energy production, just a little fuzzy on that part.

[JoeStrout]

If Bussard can achieve a model that produces net energy, how does he plan on extracting that energy?

When using the p-B11 reaction, most of the fusion products are high-velocity charged particles. You can extract their energy in fairly simple fashion using charged plates; the plates slow the ions down, generating a DC current in the process. Bussard has said that to the outside world, the fusion reactor would look like a giant battery.

With the D-T reaction, extracting the energy is much harder, since it comes mostly in the form of neutrons.

[gblaze42]

If Bussard can achieve a model that produces net energy, how does he plan on extracting that energy?

When using the p-B11 reaction, most of the fusion products are high-velocity charged particles. You can extract their energy in fairly simple fashion using charged plates; the plates slow the ions down, generating a DC current in the process. Bussard has said that to the outside world, the fusion reactor would look like a giant battery.

With the D-T reaction, extracting the energy is much harder, since it comes mostly in the form of neutrons.

Thanks Joe, so I'm guessing as long as their is a constant replenishment of proton's and Boron-11, there should be some type of equilibrium. I just have a under grad in physics and an EE by profession, so please forgive the pedantic questions.

[MSimon]

If Bussard can achieve a model that produces net energy, how does he plan on extracting that energy?

When using the p-B11 reaction, most of the fusion products are high-velocity charged particles. You can extract their energy in fairly simple fashion using charged plates; the plates slow the ions down, generating a DC current in the process. Bussard has said that to the outside world, the fusion reactor would look like a giant battery.

With the D-T reaction, extracting the energy is much harder, since it comes mostly in the form of neutrons.

Actually Joe it is the gaps between the plates that slow the alphas down in the contemplated design. It would be a linear accelerator in reverse.

[Zixinus]

So the fusion products are stopped. How do we further get rid of them altogether, so they won't bother the potential well and cause impurities in the fusion fuel?

[bcglorf]

So the fusion products are stopped. How do we further get rid of them altogether, so they won't bother the potential well and cause impurities in the fusion fuel?

The slowed down products are then pulled out by the vacuum pumps. Bussard goes over it in passing in the Google talk.

[gblaze42]

If Bussard can achieve a model that produces net energy, how does he plan on extracting that energy?

When using the p-B11 reaction, most of the fusion products are high-velocity charged particles. You can extract their energy in fairly simple fashion using charged plates; the plates slow the ions down, generating a DC current in the process. Bussard has said that to the outside world, the fusion reactor would look like a giant battery.

With the D-T reaction, extracting the energy is much harder, since it comes mostly in the form of neutrons.

Actually Joe it is the gaps between the plates that slow the alphas down in the contemplated design. It would be a linear accelerator in reverse.

This implies that the fusion products are collimated into a beam, doesn't it? wouldn't the path of alpha particle product be more random?

[bcglorf]

When using the p-B11 reaction, most of the fusion products are high-velocity charged particles. You can extract their energy in fairly simple fashion using charged plates; the plates slow the ions down, generating a DC current in the process. Bussard has said that to the outside world, the fusion reactor would look like a giant battery.

With the D-T reaction, extracting the energy is much harder, since it comes mostly in the form of neutrons.

Actually Joe it is the gaps between the plates that slow the alphas down in the contemplated design. It would be a linear accelerator in reverse.

This implies that the fusion products are collimated into a beam, doesn't it? wouldn't the path of alpha particle product be more random?

As long as the paths are uniform you can use the same idea. The alphas should all be moving on a path straight out from the centre. A spherical grid will extract that energy just like flat plates would from a unidirectional beam.

[gblaze42]

So finally,

Has their been analysis for just how many alpha by-products we need to generate enough power to break even?

If whats been said is true, it should easily calculate just how much we need to reach this.

[bcglorf]

So finally,

Has their been analysis for just how many alpha by-products we need to generate enough power to break even?

If whats been said is true, it should easily calculate just how much we need to reach this.

The scaling and the engineering are gonna have a significant impact on what the exact numbers for break even would be. Bussard's goal for the first break even device would be 1.5-2m for 100MW output. B-field strength,drive energy and magrid width are all going to have a significant impact on break even size. I believe a safe upper limit on break even alpha's needed would be to take a safe efficiency level for the direct conversion and figure from that your alphas needed for 100MW. One of the best sources for the variables involved is the report Bussard sent to Valencia:
http://www.askmar.com/ConferenceNotes/2 ... 0Paper.pdf

[rogerlam]

Actually Joe it is the gaps between the plates that slow the alphas down in the contemplated design. It would be a linear accelerator in reverse.

This implies that the fusion products are collimated into a beam, doesn't it? wouldn't the path of alpha particle product be more random?

As long as the paths are uniform you can use the same idea. The alphas should all be moving on a path straight out from the centre. A spherical grid will extract that energy just like flat plates would from a unidirectional beam.

A stupid question: I can see the charged plates decelerating the alpha's, thus alpha must have work done on the plates. But can't figure out how that translate to DC current output. Help?

[bcglorf]

A stupid question: I can see the charged plates decelerating the alpha's, thus alpha must have work done on the plates. But can't figure out how that translate to DC current output. Help?

On a really simplistic level the alpha's are always coming through the decelerating grid in the same direction. Because they are always traveling in the same direction, the current you pull from them is also always in the same direction.

[MSimon]

Another way to look at it is that if no current was pulled from the plates the voltage on the plates would rise until there was enough voltage to "repel" the ions.

[rogerlam]

Thanks for the replies people. I get the general picture now, since there is directional ion stream, there must be a current balancing it or charge will build up, right?

But I'm still stuck at this little detail: DC current always have a closed circuit, a battery must provide and drain electron at the same time (or a ground will do the draining). In our case, does the slowed down alpha's drain the electrons some how? Maybe a schematics would help, anyone know where I can find one?

Please bare with me, I major in electronics.....

[rogerlam]

OK, I've just concluded that the alpha's must come into contact with the positively charged plates and rob electrons of them to produce DC. Am I right?