Nuclear fusion by Z-pinch without Marx generator?

Question

The Marx generator was invented by Erwin Marx in 1924 (1). This electric generator is an assembly of capacitors and spark-gaps. The capacitors charged in parallel and are discharged in serie. This device generates pulses of great power without having to design a high voltage capacitor.

The first attempts to obtain nuclear fusion were the Z-pinch (2): an electric discharge of great power in a gas causes an intense heating and a strong compression. The easiest nuclear fusion can be obtained by this way with a gas mixture composed of deuterium and tritium. It is obviously a Marx generator that is used for all the experiments of Z-pinch since the origin of these tests in the years 1950.

The fusion by Z-pinch has failed (2). The duration of generated plasma appeared very insufficient: instabilities develops systematically and disperses plasma.

What is the source of these instabilities? It seems to to me that a source can be the Marx generator itself. When the Marx generator begins to work, the discharge of the first capacitor through the first spark-gap starts the cascade of discharges of following capacitors. Each spark in spark-gaps generates a pulse in the global discharge. I have found two articles that show these pulses in Marx generator discharges (4) (5). These small variations of the electric discharge are perhaps at the origin of instabilities of the plasma.

Is it possible a Z-pinch experiment without Marx generator?

(1) https://en.wikipedia.org/wiki/Marx_generator

(2) https://en.wikipedia.org/wiki/Z-pinch

(3) https://en.wikipedia.org/wiki/Plasma_stability

(4) https://www.researchgate.net/publication/260836589_Compact_180-kV_Marx_generator_triggered_in_atmospheric_air_by_femtosecond_laser_filaments/link/00b49532afe90cd3e5000000/download

(5) https://www.researchgate.net/publication/228992104_Study_of_an_Ultra_Compact_Repetitive_Marx_Generator_for_High-Power_Microwave_Applications

Answer 1

What is the source of these instabilities? It seems to to me that a source can be the Marx generator itself.

No, the instabilities seen in the early pinch systems are inherent to the plasma itself. They will occur no matter what the power source is.

In pinch devices, the plasma is held together, or "confined", by an electric current. When the current runs through the plasma it causes it to "pinch down" due to the induced magnetic field. This keeps the plasma from expanding outward, and also heats it up, which is a handy side-effect.

The problem is that the plasma will always have areas of more density and areas of less density than the average. When the current runs through the areas with higher density, the resulting magnetic field is higher, and it will pinch faster. That increases the density in that area, which increases the field even more, and so on. The result is that the plasma pinches down into a series of dots which disrupts the plasma as a whole.

It doesn't make a difference where the current comes from or what supplies it. Unless the plasma is perfectly homogeneous, this problem is going to happen as soon as there is a current.

This is similar to a ball balanced on the top of a hill. If it is displaced, it will suddenly roll to the bottom of the hill. It does not matter how you push the ball, the instability is inherent to the setup.

As we learned more about plasma, we found many more examples of these sorts of inherent instabilities, and that's why we still don't have working fusion machines 85 years after the first one.