Cosmic ray induced nuclear fusion

[CosmicKitten]

I am soooo sorry to revive this dead thread, but I have studied a bit in the past year and I have more questions...

I heard about a contest from NASA to design something that can store enough solar energy to operate a lunar rover function on the dark side of the moon during the two week(?) long lunar night. There is still a cosmic ray flux on that side of the moon, correct? If the rover had like a solar panel but instead covered with an array of coiled nanowires, if cosmic rays zipped through it would a current be induced? Or would the coil have to be moving? What if it coiled in one direction and then coiled in the other, would say a wire with current running through it induce an AC current with frequency equal to the drift velocity of the current running through it or is my understanding completely incorrect? Cosmic rays would likely experience so little resistance that they would zip through it with almost zero energy loss, but would it be possible to capture some of that energy through induction in some way? Or at the very least absorb some of the cosmic rays themselves to charge a plate, perhaps use magnets to bend electrons in one direction and protons in the other to be captured on separate plates and store voltage like a capacitor on those plates? Or would there not be enough electrons in the cosmic rays so would a plate collecting protons run a current if connected to the ground? What sort of setup would be able to capture such high energy protons in the first place? A palladium plate that would collect them to make charged palladium hydride, but that would only work for so long as the palladium is able to store extra hydrogen (plus whatever other nuclei are in the cosmic rays which might not store as well or disrupt the crystal lattice?) Could the particles be stopped and then their Bremsstrahlung radiation collected and used for energy?

 

[mfb]

Even if you find some magical way to collect all the energy of cosmic rays (you won't), 1 second in the sun is worth years in the shadow. Even starlight (the visible part) is better than cosmic rays, assuming my estimate from 2012 is correct.

 

[Vanadium 50]

Please calculate the energy you can get in joules per square meter. That will tell you an important fact.

 

[CosmicKitten]

I can't find any data for the cosmic ray energy flux on the moon or anywhere on the Earth for that matter. I know it's higher on the moon because of the lack of magnetic field and atmosphere, it would even be mostly primary cosmic rays.

What would happen if say a proton at that high of an energy hit a nucleus in a reactor full of tritium or even helium or lithium? How do you figure out the products of a nuclear reaction given the energies and isotopes of the original nuclei? Would it sustain a fusion chain reaction or would it fizzle? Are there any conceivable circumstances where an infrequent ultra high energy proton could sustain such a reaction, or at least reduce the energy input required from other sources?

What about the bremsstrahlung radiation lost in a nuclear fusion reactor, I hear it's harvested by heating the steel walls, why not cover the walls with like solar panels but with band gaps that absorb energy more efficiently in the x ray region? How well would bremsstrahlung losses have to be recovered in order for a nuclear fusion reactor to make more energy than it requires for ignition?

 

[Drakkith]

Would it sustain a fusion chain reaction or would it fizzle? Are there any conceivable circumstances where an infrequent ultra high energy proton could sustain such a reaction, or at least reduce the energy input required from other sources?

No. None. It just doesn't work this way.

What about the bremsstrahlung radiation lost in a nuclear fusion reactor, I hear it's harvested by heating the steel walls, why not cover the walls with like solar panels but with band gaps that absorb energy more efficiently in the x ray region?

To my knowledge solar panels cannot be made for the X-Ray range.

How well would bremsstrahlung losses have to be recovered in order for a nuclear fusion reactor to make more energy than it requires for ignition?

That depends on the losses due to the radiation vs the reaction rate, along with a whole lot more, like efficiency of the energy conversion process. However, you're missing a very very key point here. We haven't even hit breakeven yet, meaning that we can't even get a reaction to put out more energy than we have to put in. And this is just talking about total energy from the reaction before being harnessed, we still have to account for losses and inefficiencies.

 

[CosmicKitten]

In theory I see no reason why an x ray 'solar' cell is not possible, don't materials with band gaps in the x ray region exist? Aluminum nitride, for example, has a band gap in the deep ultraviolet; I'm sure even greater band gaps exist. And quantum dots can be made any size, could they be small enough to efficiently absorb x-rays?

And wouldn't that be because of all the energy it takes just to keep it confined? ...even in a pot of relatively cool particles, there still exist some that are 'hot' enough to overcome the Coulomb barrier and fuse. Same principle that water evaporates, that is, expels its hotter molecules, emitted at steam velocities despite the water itself being in liquid form, leaving the rest of the water cooler than it was before, you know, skimming off the far end of the bell curve to shift the broad part backwards. Similarly, if one could cook a pot of deuterium to be -just- hot enough to ionize into a plasma state, but not too hot to overcome a reasonable magnetic field, except for the very hottest ones that will simmer off at fusion-ready speeds to fire at a target... um, is such a principle in development or research?

 

[Drakkith]

In theory I see no reason why an x ray 'solar' cell is not possible, don't materials with band gaps in the x ray region exist? Aluminum nitride, for example, has a band gap in the deep ultraviolet; I'm sure even greater band gaps exist. And quantum dots can be made any size, could they be small enough to efficiently absorb x-rays?

The minimum energy for x-rays is about 100 eV's. I don't know of any materials with a bandgap near that. Aluminum nitride has a bandgap of 6.2 eV.

And wouldn't that be because of all the energy it takes just to keep it confined? ...even in a pot of relatively cool particles, there still exist some that are 'hot' enough to overcome the Coulomb barrier and fuse. Same principle that water evaporates, that is, expels its hotter molecules, emitted at steam velocities despite the water itself being in liquid form, leaving the rest of the water cooler than it was before, you know, skimming off the far end of the bell curve to shift the broad part backwards. Similarly, if one could cook a pot of deuterium to be -just- hot enough to ionize into a plasma state, but not too hot to overcome a reasonable magnetic field, except for the very hottest ones that will simmer off at fusion-ready speeds to fire at a target... um, is such a principle in development or research?

No, as the reaction rate is practically zero at that temperature. Reaction rate is a function of temperature and density. To increase the reaction rate you must increase one or both of those parameters, and either way it takes energy to do so. And before you ask, even if we compress the plasma to a very dense state the temperature is still far too low to generate any appreciable reaction rate. You're talking about a few thousand kelvin, whereas we need the plasma at millions to hundreds of millions of kelvin. For comparison, the D-T reaction rate peaks around 800 million k. See below.

We are trying to hit the "sweet spot", where the temperature and density are high enough to generate more fusion power than we use to confine and heat it. We have yet to succeed for a large number of very complicated reasons.

 

[mfb]

And quantum dots can be made any size, could they be small enough to efficiently absorb x-rays?

They are made out of atoms, so the minimal size is the size of an atom - way too large for x-rays. For the same reason, the band gaps cannot reach the x-ray range.

...even in a pot of relatively cool particles, there still exist some that are 'hot' enough to overcome the Coulomb barrier and fuse.

Define "relatively". There are atoms with 10-20 times the average energy, no problem. A few atoms will even have up to 50 times the average energy. But fusion needs more than 1 million times the average energy of room temperature. That won't happen within the lifetime of the sun, not even for a single atom, even if your room temperature storage is the whole earth/moon system.
Even the fusion experiments, with ~100 million K, are below the Coulomb threshold and rely on particles with a high-than-average kinetic energy together with tunneling processes.

 

[fusion2022]

Cross section of any element is too little in the cosmic ray energy region
UV and X rays work better