Plasma Injectors in Recent Navy Work

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mattman
Posts: 456
Joined: Tue May 27, 2008 11:14 pm

Plasma Injectors in Recent Navy Work

Postby mattman » Tue Jul 07, 2015 2:24 pm

Hello All,

Here is the description of the plasma injectors, from the paper:

The plasma injectors consist of two co-axial plasma guns with an anode to cathode gap spacing of 2 mm utilizing JXB plasma acceleration.[10] The plasma guns use solid polypropylene lm with 4 m thickness instead of more common gas injection to generate high pressure plasmas in a very short time. The amount of material injection is controlled by the number of film layers; two layers were chosen for the work presented here. The plasma guns are constructed with tungsten electrodes and boron nitride insulators to minimize erosion and impurity injection. Each gun is powered by a high voltage capacitor and operates with 60{150 kA of gun current using an Ignitron switch. Each gun is capable of injecting high pressure plasma with up to 500 MW pulse power from the capacitor and pulse duration between 5-10 microseconds.


Here is what they looked Like:

Image

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Putting this altogether

Image

mattman
Posts: 456
Joined: Tue May 27, 2008 11:14 pm

Re: Plasma Injectors in Recent Navy Work

Postby mattman » Tue Jul 14, 2015 2:18 am

Guys - I will take any feedback on this you have on this. I have two questions:

1. Paschan Arching happens when the system is on that line, right? Not over? Not Under?
2. The Magnetic field plot looks wrong. It should be easy to check, its the B-field around a wire
3. If the plastic vaporizes instantly, is it still valid to model the voltage field as In the plastic wrap?

Thanks


Plasma Emitter:

It is tough to make a pressurized plasma. Indeed, this is why cusp experiments have failed in the past [14, 2]. The team must have tried several things, before settling on the final plasma emitter. The final tool may have seemed like overkill. The plasma emitter flung vaporized carbon and hydrogen into the polywell. It pulled this off by vaporizing a polypropylene sheet (think a sheet of plastic wrap). A picture of this tool is shown below.

Image

This device is brilliantly designed. At full power one hundred and fifty thousnad amps flowed along the outside [12]. Electrons move into the center and jump across the gap. It is highly unlikely that any current will arch or spark across the air gap [22,23]. All the current flowed across that plastic sheet. The tens of thousands of amps vaporize the plastic; forming a carbon and hydrogen plasma. Once across the gap, the current leaves. It flows along the inner cathode and out of the device. As it leaves, it generates a magnetic field.

The brilliance of this device, is that three effects happen simultainously: the plastic wrap is fully vaporized, an electric field forms across the gap and a magnetic field spins around the center. When combined, these effect fling a plasma outwards. Flinging happens because of the Lorentz force; also known as the J X B force [24]. When an electric field is at a right angle to a magnetic field, ions are forced outwards.

This device is easy to model. Sparking can be modelled using Paschen law [23]. Paschens law tells us if electrons will leap across an air gap - we quickly see this will not happen. That means all the current moves through the plastic sheet. The sheet vaporizes instantly – becoming a cloud of plasma. This is because the energy needed to break the chemical bonds and full ionize the gas is only hundreds of joules and far more energy passes by. Once across, the current travels down the cathode making a magnetic field. This field can be modelled using the biot-savart law for a single wire. This is plotted below. Next, we can model the resistance of the plastic sheet using the resistivity of circular sheet of polyproplene [25, 26]. With this, we can estimate the eletric field; which is also plotted below.

Image

The plasma emitter experiences a huge amount of watts pass through it, during each shot. This heats up the inner metal surface, causing the tungsten to chip away [2]. This is known as thermionic emission; and it leads to a poisoning of the plasma with tungsten ions.

mattman
Posts: 456
Joined: Tue May 27, 2008 11:14 pm

Re: Plasma Injectors in Recent Navy Work

Postby mattman » Tue Jul 21, 2015 6:38 pm

Guys, the new version is far better.

You can read the updated Version Here: http://qr.ae/RIT9ZS


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