What exactly is z-pinch fusion

[PlasmaSphere]

I have been reading a lot about Z-pinch fusion recently, and i am still not entirely sure what it is. Is it a completely new type of fusion? is it in any way comparable to the fusion that is thought to be happeneing in the sun? or are they completely different processes?

The Z machine has achieved it, i want to know what the differences are of this fusion process to to normal fusion.

 

[Troels]

I have been reading a lot about Z-pinch fusion recently, and i am still not entirely sure what it is. Is it a completely new type of fusion? is it in any way comparable to the fusion that is thought to be happeneing in the sun? or are they completely different processes?

The Z machine has achieved it, i want to know what the differences are of this fusion process to to normal fusion.

A pinch effect is something that happens when you run a current through a plasma. This generates a circumfential magnetic field like any wire, but since the charges in plasmas are free to move, they will be pressed - "pinched" if you like - together as a result of the magnetic force.

The Tokamak design (the large donut) of a fusion reaktor, for instance, would not work was it not for a clever use of Z-pinch. It turns out that a toroidal magnetic field alone cannot confine a plasma, let alone compress it to achieve fusion. So you run a current through the plasma in the donut, that both serves to keep the plasma hot and create a Z-pinch that forces the plasma towards the center of the donut-tube, compressing it to fusion.

So the morale is: Z-pinch is not a specific type of fusion proces, rather is is a way of plasma confinement and compression (and not so very new either - dates back to the 70'ies). The sun on the other hand, takes care of that problem simply by being so massive that it's gravity does the job.

 

[PlasmaSphere]

So the morale is: Z-pinch is not a specific type of fusion proces, rather is is a way of plasma confinement and compression. The sun on the other hand, takes care of that problem simply by being so massive that it's gravity does the job.

So is the sun fuelled by a Z-pinch process? I thought that was nuclear fusion?

I was wondering also, does the type of particles that are used to release this energy matter significantly? or can it be achieved with any sort of element?

since the term fusion is quite general, i see that general fusion is described as; "The process of combining nuclei together with a release of kinetic energy", does it matter what particles are used to release this energy? I would expect that certain particles are more suited to releasing energy than others, i just want to know why that is, or which are best for achieving the Z-pinch fusion effect.

 

[JeffKoch]

Z-pinch machines like the Sandia Z machine emit copious x-rays, and these x-rays can be used to drive inertial confinement fusion implosions(http://en.wikipedia.org/wiki/Inertial_confinement_fusion). The x-rays from the pinch could be used directly to drive the implosion, or they could be used to induce secondary x-ray production in an exterior "can" to drive the implosion - the latter geometry has the advantage of reducing the very high-energy x-ray irradiation of the capsule (causing pre-heating and reduce compression), and the disadvantage of efficiency losses in the exterior can. The overall process is similar to laser-driven inertial confinement fusion (http://en.wikipedia.org/wiki/National_Ignition_Facility) - big Z-pinch machines deliver a lot more x-rays, but over much longer timescales and with less precision. The fusion reactions contemplated in any near-term fusion machine are deuterium-tritium fusion; in contrast, stars like the sun generate energy through different reactions like the proton-proton chain (http://en.wikipedia.org/wiki/Proton-proton_chain_reaction).

 

[Hurkyl]

So is the sun fuelled by a Z-pinch process? I thought that was nuclear fusion?

He was saying that the Sun achieves plasma confinement and compression through gravity.

 

[PlasmaSphere]

He was saying that the Sun achieves plasma confinement and compression through gravity.

ahhh, i see. So the centre of the sun has sufficient pressure to fuse atoms without there being a need for high energy current input in such machines as the Z-machine.

http://en.wikipedia.org/wiki/Z_machine

When the Z machine fires, the energy from a 20-million-ampere electrical discharge vaporizes an array of thin, parallel tungsten wires, creating plasma. Simultaneously, the electrical current creates a powerful magnetic field that compresses and implodes the plasma by means of a z-pinch process.

So the huge pressure at the core of sun bypasses this part of the process and produces fusion directly, without the need for the electric current input or magnetic confinement?

 

[Troels]

So the huge pressure at the core of sun bypasses this part of the process and produces fusion directly, without the need for the electric current input or magnetic confinement?

Jep, that's more or less it.

 

[JeffKoch]

So the centre of the sun has sufficient pressure to fuse atoms without there being a need for high energy current input in such machines as the Z-machine.

Not quite, the implosion of the tungsten wire plasma in the Z-pinch isn't the same as the implosion of a capsule containing DT. The Z-pinch effect doesn't directly confine or drive the fusion plasma, as it does in a tokamak - here, the wire implosion just generates a lot of x-rays, and those x-rays drive the implosion of a DT capsule. Instead of using gravity, the pressure to drive the fusion implosion comes from ablation of the capsule, caused by intense irradiation by the x-rays produced by the Z-pinch. A couple links:

http://www.sandia.gov/capabilities/pulsed-power/prog_cap/pub_papers/000191a.pdf
http://www.sciencedaily.com/releases/2003/04/030407073625.htm

 

[mheslep]

The pinch effect was first observed in 1904 in liquid conductors. http://www.fusionnow.org/dolan.html" is on pinches, a good fundamental description.