Atoms whose protons have been stripped off can fuse?

[CrazedMathematician]

You didn't comment on http://www.focusfusion.org Do you think it's for real? I searched on "plasma focus" and it seems like a real device. Also, do you know anything about Colliding Beam Fusion? http://fusion.ps.uci.edu/beam/introb.html It also looks promising.

 

[Morbius]

You didn't comment on http://www.focusfusion.org Do you think it's for real? I searched on "plasma focus" and it seems like a real device.

CrazedMathematician,

I haven't heard of this before - and one would think someone in the
scientific community would have.

I don't see many research labs like LLNL with a website that is hooked
to PayPal to accept contributions.

I'm dubious.

Also, do you know anything about Colliding Beam Fusion? http://fusion.ps.uci.edu/beam/introb.html It also looks promising.

Looks a little like the Mirror Fusion Test Facility that LLNL had in
the 1970s - except no yin-yang magnets:

http://www.specktech.com/MFTF.html

That project didn't get anywhere - that part of the Lab is still blocked
off for the dismantlement effort.

Dr. Gregory Greenman
Physicist

 

[Astronuc]

Focus Fusion claims are indeed questionable.

I addressed them in this thread - Plasma focus fusion
https://www.physicsforums.com/showthread.php?t=57321

Specific impulse is in some sense a measure of 'effectiveness' (and not really efficiency) of the utilization of propellant mass, or more specifically, mass flow rate to achieve thrust. Furthermore, it is not a measure of the overall 'system efficiency', which includes energy production/conversion efficiencies.

Yes, a plasma has high temperature/kinetic energy per unit mass, however the densities and mass flow rates are extremely small.

A plasma density is about 10¹⁴ particles/cm³, and that is about one-millionth of the density at STP (~3x10¹⁹ molecules/cm³), so a high Isp does not buy much if the mass flow rates are extremely small.

2N thrust is very small, if a spacecraft has a mass of 1000 MT.

One must be very careful in applying basic stoichiometric equations to complex propulsion systems. Fusion reactors are massive structures.

 

[Morbius]

Specific impulse is in some sense a measure of 'effectiveness' (and not really efficiency) of the utilization of propellant mass, or more specifically, mass flow rate to achieve thrust. Furthermore, it is not a measure of the overall 'system efficiency', which includes energy production/conversion efficiencies.

Astronuc,

Exactly correct.

Specific impulse tells you how well you are using a given amount of
reaction mass.

But it doesn't tell you how well you are using your energy.

For high specific impulse, you want a low mass propellant.

As a thought experiment; image we use a cyclotron to accelerate
deuterons, which we then blast out the back of the vehicle.

You may have a high specific thrust owing to the low mass of the
propellant; however - a cyclotron is terribly inefficient from an
energy economy standpoint. You are going to be depositing a lot
of energy in your magnetic field windings...

If you had a source of electricity - you sure wouldn't want to waste it
by heating up the windings and pole pieces of the cyclotron.

Using a cyclotron as a "rocket" is an obvious loser.

Too bad the tokamak as a "rocket" doesn't fair much better.

Dr. Gregory Greenman
Physicist

 

[sid_galt]

If a normal hydrogen nucleus is hit with a neutron, does it combine to form deuterium?

 

[Morbius]

If a normal hydrogen nucleus is hit with a neutron, does it combine to form deuterium?

Sid,

That is ONE of the things that can happen.

If it does - it is called "radiative capture" because the incident neutron is,
of course, not bound to the proton. When the neutron and proton combine
to form deuterium - a bound state - there will be excess energy. That
excess energy will be radiated away as a gamma - hence radiative capture.

The notation is:

H(n,\gamma)D

But that's not the only thing that can happen. The neutron can scatter
off the proton. That's why water is used as a moderator in nuclear
reactors. One wants to slow the neutron down, since the fission
cross-section is greater at low energy than at high. The way one does
that is to let the neutron scatter off the proton - thereby losing energy.

Dr. Gregory Greenman
Physicist

 

[sid_galt]

Although muon catalyzed fusion is not of much practical use, how is it affected by scattering?
If the problem of scattering is significantly lower for muons, is it because of its charge, its mass or both?

 

[Morbius]

Although muon catalyzed fusion is not of much practical use, how is it affected by scattering?
If the problem of scattering is significantly lower for muons, is it because of its charge, its mass or both?

sid,

Muons don't do anything to combat the nuclear scattering problem.

It's not the muons that are scattering - it's the nuclei that are going to fuse.

The only thing muons do is that they "orbit" closer to the nucleus than does
an electron - therefore they reduce the radius at which the fusing atom
is electrically neutral.

Muons only help out on Coulomb repulsion - and, of course, Coulomb
scattering.

Muons don't do anything to help out with nuclear processes - like nuclear
scattering.

Dr. Gregory Greenman
Physicist

 

[sid_galt]

Thanks for the Info