X-Ray shell

[Brian H]

While reading this article on graphene http://www.nanowerk.com/news/newsid=10425.php it struck me that it might end up being a fine material to use to capture and draw off the released electrons between the foil layers in the X-ray shell. It is very robust, and has almost zero resistance, and of course is very lightweight — all good things!

[Aeronaut]

You’ll need an insulator for that, Brian. The x-ray collector works like a capacitor.

[Brian H]

Aeronaut wrote: You’ll need an insulator for that, Brian. The x-ray collector works like a capacitor.

In what respect like a capacitor? The electrons knocked loose by X-rays are drained by grids between foil layers; I am suggesting use of the graphene for the grids. The last thing you want to do is insulate them.

[Aeronaut]

Brian H wrote:

You’ll need an insulator for that, Brian. The x-ray collector works like a capacitor.

In what respect like a capacitor? The electrons knocked loose by X-rays are drained by grids between foil layers; I am suggesting use of the graphene for the grids. The last thing you want to do is insulate them.

The patent compares the converter assembly to a capacitor- the foils are your grids, collecting the electrons. Each of the foils is a different thickness to reduce the energy of x-rays with enough energy to penetrate them. Personally, this reminds me of control grids in a vacuum tube, all the way down to the biasing network.

Put another way, since the foils conduct very well, what is the gain of designing and producing another 1,000 or so conducting layers?

But no matter what the end design is, CVD is the only production process with even a chance of building these assemblies reliably. I suspect that this assembly is going to be the vast majority of the production cost.

[Brian H]

Aeronaut wrote:

You’ll need an insulator for that, Brian. The x-ray collector works like a capacitor.

In what respect like a capacitor? The electrons knocked loose by X-rays are drained by grids between foil layers; I am suggesting use of the graphene for the grids. The last thing you want to do is insulate them.

The patent compares the converter assembly to a capacitor- the foils are your grids, collecting the electrons. Each of the foils is a different thickness to reduce the energy of x-rays with enough energy to penetrate them. Personally, this reminds me of control grids in a vacuum tube, all the way down to the biasing network.

Put another way, since the foils conduct very well, what is the gain of designing and producing another 1,000 or so conducting layers?

But no matter what the end design is, CVD is the only production process with even a chance of building these assemblies reliably. I suspect that this assembly is going to be the vast majority of the production cost.
My understanding was that the foils were separated by grids, which carry off the dislodged electrons. The foils themselves are not the “grids”.

[Breakable]

Insulation is required so that the electrons would not recombine with the holes where they originated.

[Brian H]

Breakable wrote: Insulation is required so that the electrons would not recombine with the holes where they originated.

That makes no “circuit sense” to me. If an electron is dislodged from a foil molecule by an X-ray, it must be in contact with the conductive grid which drains off the power in order to leave the shell as part of a current. Insulation would block that process at the source. Once in the grid wiring/conductor, the path of (literally) least resistance would be to exit the shell through the grid connection. The foils would be grounded to supply electrons to fill the “holes”.
Actually, here’s what the patent says:

The x-ray collector 46 includes one or more metal layers 48a-48i separated by interstitial layers 50a-50h. The composition of the one or more metal layers 48a-48i may vary depending on the specific embodiment. For example, metal layers 48a, 48b and 48c contain aluminum, metal layers 48d and 48e contain copper, while metal layers 48e, 48f and 48g contain tungsten. Similarly, the composition of the interstitial layers 50a-50h may vary depending on the specific embodiment. For example, interstitial layers 50a, 50b and 50c may be aluminum or beryllium, while 50g is tungsten. Although the skilled artisan will recognize the above examples are intended for illustrative purposes and that other metals may be used and in different orders and compositions.

[Breakable]

Lets talk about a path of least resistance.
If the insulator between the layers provides less resistance than the circuit itself,
then the probability that the electron will jump the insulator and recombine instead of going trough the circuit is higher.
Grounding one layer does not solve the problem. This results in the statistical number of holes in the plate equal to the number of holes in the ground. The potential between the plates stays the same.
Do you think there are initially no holes in the ground? Well then you just added them, and now they can recombine electrons. I am not sure how this will affect recombination, I just guess you will have a higher place for recombination (the whole earth), and when that happens ( a lightning strikes somewhere) – no more electricity for you!

Ok now if you don’t want any dielectric between the layers, this means you want a conductor there, as these are mutually exclusive.
This means the layers are connected and have the same potential, which means there are no current running between them.
This makes no sense in electricity generation.

The only thing here that makes sense is choosing the right thickness, size and configuration of plates and the dialectic material. The result will be that it will operate as a Condensation that is charged by generated X-Ray. I have some ideas what kind of configuration you might want to use to reduce the recombination, but I wont tell anyone until I am hired as an Scientist in FF team 😀

[Brian H]

Breakable wrote: Lets talk about a path of least resistance.
If the insulator between the layers provides less resistance than the circuit itself,
…

What a remarkable assumption! Clearly not relevant, of course. :cheese:

[Aeronaut]

I think what Breakable meant by “path of least resistance” is a biasing network, similar to biasing grids in a tetrode or pentode vacuum tube. Back then we wanted to minimize grid current. Now we need to maximize it in order to reach and exceed unity.

The most effective collecting layers will tend to be more negative, even before adding components to the biasing network. If we’re dealing with a fluctuating ‘signal’ (current flow) we may be able to use fast switching and/or capacitors to minimize power loss.

Frankly, I’m having problems seeing foils carrying huge currents. Anybody want to take a stab at the power, voltage, and/or current that Baby will output from the X-ray converter?

[jamesr]

Collecting the energy of the X-Ray photons as as movement of electrons (ie. an electric current) involves a few processes.

First the X-Ray photon has to interact with an atom. The photoelectric absorption probability rises with the 4th power of atomic number of the material, so low atomic number materials (like carbon) do not interact well with X-rays. Hence the fleshy bits of people are dark on medical xray negatives & the calcium in bones is light.

So we want the x-ray photon to be absorbed in the high atomic number material (eg. tungsten). This results in an electron being emitted from the atom with pretty much the same energy as the photon had, ie 10-100keV. We want this electron to escape the foil and deposit its energy by exciting say 10000 secondary electrons of other atoms in the dielectic/insulator material.
Since we want the foils thin enough for the primary electron to esacpe the probability of an X-Ray being absorbed in any particular foil is still low – so we need lots of them.

On there own these secondary electron/hole pairs would just recombine not giving us any current. So by applying a bias voltage between the foils, the electrons & holes are drawn by the electric field between the foils creating a movement of charge and hence an electric current.

[Brian H]

jamesr wrote: Collecting the energy of the X-Ray photons as as movement of electrons (ie. an electric current) involves a few processes.

First the X-Ray photon has to interact with an atom. The photoelectric absorption probability rises with the 4th power of atomic number of the material, so low atomic number materials (like carbon) do not interact well with X-rays. Hence the fleshy bits of people are dark on medical xray negatives & the calcium in bones is light.

So we want the x-ray photon to be absorbed in the high atomic number material (eg. tungsten). This results in an electron being emitted from the atom with pretty much the same energy as the photon had, ie 10-100keV. We want this electron to escape the foil and deposit its energy by exciting say 10000 secondary electrons of other atoms in the dielectic/insulator material.
Since we want the foils thin enough for the primary electron to esacpe the probability of an X-Ray being absorbed in any particular foil is still low – so we need lots of them.

On there own these secondary electron/hole pairs would just recombine not giving us any current. So by applying a bias voltage between the foils, the electrons & holes are drawn by the electric field between the foils creating a movement of charge and hence an electric current.

Which is why I thought graphene as the dielectric, as it conducts almost perfectly and is thermally and physically robust, would be very suitable. Not to mention vanishingly thin and lightweight.

[jamesr]

The dielectric must be an insulator to maintain bias voltage between foils, otherwise the whole thing will just short out. By an insulator I mean a material with a band gap energy of above a few eV. A semi-conductor for comparison has a band gap of the order of 1eV between the valence & conduction band, and a conductor has negligible or no gap at all. So at normal room temperatures eg 300K which corresponds to 0.025eV of energy for the average electron almost none are excited into the conduction band in an ‘insulator’. However if they are given a kick by the photo-electron from the x-ray absorption, an electron in the ‘insulator’ can gain the few eV needed to be excited into the ‘conduction’ band and so becomes mobile. The high energy photo-electron loosing a corresponding few eV in each interaction.

After a few thousand interactions the high energy photo-electron will have excited lots of secondary electrons and have slowly lost all its energy. This takes time (a few pico seconds) so the dielectric needs to be thick enough for all the energy to be deposited in the dielectric – I’m guessing a few to tens of microns.

If the photo-electron were to get to the next foil (or scatter back to the one it came from) then the atoms excited in the foil will not result in a movement of charge across the electic field created by the bias voltage (the foil being a conductor will all be at the same potential and hence no E-field within it and no motion of electron/hole pairs created, so they will just recombine locally with no nett current). So the proportion of all the original photo-electron’s energy deposited in the dielectric limits the the x-ray energy capture efficiency.

NB. all of this is just based on my understanding of X-ray absorption, and so how to get a measurable current from such an interaction, not on the specifics of the patent

[QuantumDot]

White graphene or hexagonal boron nitride is a insulator, can survive harsh conditions, and boron 10 can absorb neutrons.

While currently expanse like graphene which recently developed a roll to roll processing method which should really bring down its price, so it still needs research but i have read that you can tune it band gap by mechanical straining it.

Quantum dots are also some thing that seems to fit the bill for the insulator since you can tune its band gap by size, and material selection, and you can also make it into an aerogel which means that you might be able to simply have a metal aerogel combine with a metal chalcogenide aerogel to make your onion to absorb the x-rays.

[Author]

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