Atoms whose protons have been stripped off can fuse?

[sid_galt]

A plasma consists of both ions and uncharged particles of gases. Is it possible for the uncharged particles to fuse or only atoms whose protons have been stripped off can fuse?

 

[so-crates]

Do you mean atoms whose electrons have been stripped off? I imagine the answer is yes, since fusion processes take place for heavier atoms, and I imagine ti would be next to impossible to strip off all the electrons before fusion takes place. This is just a guess and I am not a physicist though. I would ask over on one of the physics forums, like Nuclei and Particles.

 

[Morbius]

A plasma consists of both ions and uncharged particles of gases. Is it possible for the uncharged particles to fuse or only atoms whose protons have been stripped off can fuse?

sid_galt,

Not quite.

A plasma consists of ions and electrons, and neutral particles.

The ions and electrons are charged - however the net charge on the
plasma is zero because the number of positive charges [ ions ] equals the
number of negative charges [ electrons ].

However, if the uncharged neutral nuclei are hit by a proton or ion of
sufficient energy - you get fusion.

In essence, that's how fusion was first produced in particle accelerators
like cyclotrons - fast protons hit a target that was cold and uncharged.

All that matters is that the two fusing nuclei hit each other with enough
energy. The electrons don't matter - at the nuclear scale - they are a
long way away, and don't take any part in any reactions concerning the
strong nuclear force.

Dr. Gregory Greenman
Physicist

 

[Morbius]

Do you mean atoms whose electrons have been stripped off? I imagine the answer is yes, since fusion processes take place for heavier atoms, and I imagine ti would be next to impossible to strip off all the electrons before fusion takes place. This is just a guess and I am not a physicist though. I would ask over on one of the physics forums, like Nuclei and Particles.

so-crates,

No - it's easier to strip off the electrons than it is to get fusion.

You can have a "fully ionized plasma" and still not have fusion.

Fusion is definitely the more difficult of the two.

Dr. Gregory Greenman
Physicist

 

[NEOclassic]

Just a friendly greeting

A plasma consists of ions and electrons, and neutral particles.

The ions and electrons are charged - however the net charge on the
plasma is zero because the number of positive charges [ ions ] equals the
number of negative charges [ electrons ].

Hi Dr GG,
About a year ago, I was doing a study (in the microwave oven in my home kitchen) that was less an ionization phenomenon than one of the kinetic theory of molecular gases. Let me describe what I discovered (I do have a video camera record): Most molecular gases when caught in an ordinary "round" latex balloon will tend to rise or fall (e.g., ~five liters of freon gas that may have been partially, although invisibly condensed, countered more than est. 30 or more liters of "party grade" Helium.) in the Texas environment and some of the lighter-than-Nitrogen gases such as methane are easily shown to rise; however, methanol or ammonium or water molecules must be de-condensed and putting these liquids into balloons might be a method of making them molecular by simply radiating them in a kitchen microwave oven. I didn't get around to anything but ordinary faucet water - except a very small amount of ammonium hydroxide in a small round balloon made such a fireworks (light flashes) display that I decided not to even mess with methanol because of retained oxygen in the ballon. If the water sample that was inserted in the balloon before microwave radiation was too large, the fact that all the water molecules were evolved at the same moment usually meant the balloon would burst before human control could shut the process down. If too small the molecular volume ceased growing when the sample was exhausted and recondensation occurred - an important fact was revealed when it was noticed that a non water gas, probably carbon dioxide which is renowned to be highly soluble in water did not recondense. When the charge was just right M/L, and the latex was expanded to some ideal thickness, the molecular water gas would flow through the pores in the latex and the condensation of the water outside the balloon would occur but not without the volumetric collapse of the plastic container in which the process was isolated - it was the plastic bottle that previously held 40 ounces of peanut butter.

When I ran out of round balloons I started using "bird shaped" latex balloons that had a protusion of a head in one direction and a tail in the opposite direction - partial recondensation apparently was happening and that was evidenced by the bird figure rocking more or less continually.

I finally got down to the long slender latex balloons that I charged with some ideal amount of water and which I placed in the bottom of the tightly closed plastic bottle. With this arrangement I was to be royally entertained by a truly plasma gas which can only be explained, I surmise, as follows: the long slender balloon which was actually shorter than the periphery of the cylindrical bottle, grew plumper and longer with radiation and ultimately over lapped its opposite end thus making a circular conducting path (that was not the slightest impeded by the two layers of latex between the ends) and which lighted up magnificently but seemed somewhat unsteady - possibly because of the pulsing wave nature of the radiant source. There can be no doubt, I believe, that ionization of water molecules or even atomic fragmentation might have occured.
If I still have your attention I would like to ask about your source of a LANL report that showed that there was sufficient unburned plutonium 239 in a spent fuel rod to make a so-called "nuke".

Incidentally, I finally got a 9-inch round balloon to rise in the microwave environment because of water molecules or ionic plasma - Of course, I realize that the volatility of whaterver gas is there, is also dependent on the elevated temperature, but then at any lower temperature condensation happens. Thanks for your audience, Jim Osborn

 

[SpaceTiger]

A plasma consists of both ions and uncharged particles of gases. Is it possible for the uncharged particles to fuse or only atoms whose protons have been stripped off can fuse?

In fact, this happens very rapidly in supernova remnants. The elements heavier than iron are built up by colliding neutrons with with charged nuclei. The "neutron-heavy" isotopes then beta decay to form elements with more protons.

 

[sid_galt]

Thanks for the help

 

[hitssquad]

Microwave vs ionizing radiation; steam vs plasma

A plasma consists of ions and electrons, and neutral particles.

About a year ago, I was doing a study (in the microwave oven in my home kitchen) that was less an ionization phenomenon

It was not an ionization phenomenon at all. Microwave radiation is non-ionizing.
http://google.com/search?q=radiation+non-ionizing+microwave


What you made in your balloons was steam, not plasma.

 

[Morbius]

It was not an ionization phenomenon at all. Microwave radiation is non-ionizing.
http://google.com/search?q=radiation+non-ionizing+microwave


What you made in your balloons was steam, not plasma.

hitssquad,

I agree - microwave radiation is non-ionizing.

You need to get to frequencies in the upper ultra-violet or X-rays and
above to be ionizing.

Neoclassic certainly did not make a plasma with his microwave.

Dr. Gregory Greenman
Physicist

 

[Uno Lee]

If I put a florescent bulb (with all the external metal parts removed) in a micro-wave oven, wouldn't it glow? Isn't this ionization?

 

[NEOclassic]

I didn't quite finish

hitssquad,

I agree - microwave radiation is non-ionizing.

You need to get to frequencies in the upper ultra-violet or X-rays and
above to be ionizing.

Neoclassic certainly did not make a plasma with his microwave.

Dr. Gregory Greenman
Physicist

Hi again good Dr.

After I discovered that my water sample expelled disolved carbon dioxide I chanced, while thinking that the radiation created merely molecular water, that to test the process as a desalinization thing, might be of interest. Noting that the salt remained crystallized in the balloon alright but that the residual freed CO2 was still in the balloon. I was just thinking that I might adjust the solubility constant of CO2 to hopefully reduce the retained volume. To that end I saturated another identical sample of the saline solution with Sodium bi-carbonate. There was such an elegant flashing light display that I never noticed whether or not the CO2 gas had disappeared. This experiment had been conducted in a closed plastic bottle and in a 7" round latex balloon. The volume of the original sample was .05 milliliters. The plastic had been grotesquely misshapen, The volume of desalinated water was > 0.075 ml, not counting a patina of visible surface moisture and inside the balloon was a mixture of white and yellow crystals the latter of which I might surmise were simply Sodium Carbonate. I believe that the magnetic radiation was somehow responsible for the redox that removed the proton from the bicarbonate and created half of a new water molecule with it.

Perhaps electrons are not completely removed but in order to get a photon when a simply excited electron hits that massless quantum field is certainly evidence of some excitement force. Another recent contributor to this string has pointed out truthfully that halogen gas in light bulbs as well kernel gases in bulbs light up in a pulsed sort of way even when an incandescent filament has already been burned out.

May I suggest that those of the responders to my little experiment who doubt my veracity or my speculations that for less than a couple of bucks for balloons mostly and the family microwave oven, you too can become the happy fool you accuse me of being. I have pictures of the light and I will listen to any sensible argument that can explain light production as a consequence other than that proposed here. Cheers, Jim Try it, its rather cheap and you'll have more fun than you've had since Jr High science.
P.S. Dr. I would dearly appreciate the source of that "nuke" from spent fuel rod item. Thanks.

 

[Uno Lee]

I didn't get around to anything but ordinary faucet water - except a very small amount of ammonium hydroxide in a small round balloon made such a fireworks (light flashes) display that I decided not to even mess with methanol because of retained oxygen in the ballon.

Do microwaves transmute into electricity when they hit metal? I think the ammonium ion behaves like a metal, thus explaining the "light flashes." I don't think (though I wouldn't want to try) that the methanol would ignite unless there was a metal (or metal-like ion) in the oven too.

 

[Davorak]

I agree that NEOclassic did not ionize anything with the microwave. However he did create a plasma by adding ammonium hydroxide to water. The technical definition of a plasma does not require an atomic ionization to be occur. Salty water is consider to be a plasma.

The microwaves then pulled the ions away from each other. The sparking he observed happen when the solution(or vapor) reached the break down voltage, causing an arc.

Edit:
NEOclassic much of what you say is filled with gramatical errors. I am certainly not great at this either. However the gramatical errors make it hard to understand you. I sugest you reread your post before you post.

 

[Uno Lee]

The microwaves then pulled the ions away from each other. The sparking he observed happen when the solution(or vapor) reached the break down voltage, causing an arc.

Is this why a metal spoon will spark in the microwave?

 

[Davorak]

Yes but in metal the electrons are moved around and the ions will stay still.

 

[Morbius]

I agree that NEOclassic did not ionize anything with the microwave. However he did create a plasma by adding ammonium hydroxide to water. The technical definition of a plasma does not require an atomic ionization to be occur. Salty water is consider to be a plasma.

Davorak,

A physicist would not call that a plasma.

Yes, salt in water disassociates into positive ions and negative ions -
but that is not a plasma.

http://whatis.techtarget.com/definition/0,,sid9_gci864603,00.html

In a plasma, the negaive charges are free electrons - you don't have
that in salty water - all the electrons are still bound to atoms.

Dr. Gregory Greenman
Physicist

 

[hitssquad]

Salty water is consider to be a plasma.

A plasma is a type of gas. Water is a type of liquid.

 

[Davorak]

I just took undergrad plasma physics last semster and batery acids as well as electons in plasma where considered a plasma.

An ionized gas is certainly the most common definition on the web.

Another defintion would be:
Plasmas are conductive assemblies of charged
particles, neutrals and fields that exhibit collective effects. Further, plasmas carry electrical currents and generate magnetic fields. Plasmas are the most common form of matter, comprising more than 99% of the visible universe.

But I like the defintion:
electromagnetic (Maxwell-Boltzmann)** systems
http://www.plasmas.org/basics.htm

Also disscused before:
https://www.physicsforums.com/archive/topic/t-59693_How_is_cold_Plasma_possible?.html

 

[Morbius]

I just took undergrad plasma physics last semster and batery acids as well as electons in plasma where considered a plasma.

Davorak,

You took undergrad plasma physics last year - and I have a doctorate
from MIT and work in plasma physics at Lawrence Livermore.

Salt in water is just an ionic solution.

What gives a plasma its unique properties is that sea of free electrons.

You have electrons that are not bound to atoms - therefore they are able
to move more freely - have longer mean free paths.

They are similar in many respects - but an ionic solution like salty water
or battery electrolyte is NOT a plasma.

[Gads - what are they teaching these days.]

Dr. Gregory Greenman
Physicist

 

[russ_watters]

I just took undergrad plasma physics last semster and batery acids as well as electons in plasma where considered a plasma.

But I like the defintion:
electromagnetic (Maxwell-Boltzmann)** systems
http://www.plasmas.org/basics.htm

Not to beat this horse too much more, but neither that link you provided, nor the PF thread referenced support your assertion.

 

[Astronuc]

Unfortunately out there in the world, there are other definitions for plasma.

1. a.The clear, yellowish fluid portion of blood, lymph, or intramuscular fluid in which cells are suspended. It differs from serum in that it contains fibrin and other soluble clotting elements.
b. Blood plasma.
2. Medicine. Cell-free, sterilized blood plasma, used in transfusions.
3. Protoplasm or cytoplasm.
4. The fluid portion of milk from which the curd has been separated by coagulation; whey.
5. Physics. An electrically neutral, highly ionized gas composed of ions, electrons, and neutral particles. It is a phase of matter distinct from solids, liquids, and normal gases.

However in the context of Physics, and this is PhysicsForums, and particularly with respect to fusion, definition 5 is the appropriate definition.

 

[Morbius]

I just took undergrad plasma physics last semster and batery acids as well as electons in plasma where considered a plasma.

An ionized gas is certainly the most common definition on the web.

Plasma as defined by the Plasma Dictionary at
Lawrence Livermore National Laboratory:

http://plasmadictionary.llnl.gov/terms.lasso?-MaxRecords=1&-SkipRecords=4&-SortField=Term&-SortOrder=ascending&-Op=bw&ABC=P&page=detail

"Term: Plasma Definition: Known as the "Fourth State of Matter", a
plasma is a substance in which many of the atoms or molecules are
effectively ionized, allowing charges to flow freely. Since some 99% of
the known universe is in the plasma state and has been since the Big Bang,
plasmas might be considered the First State of Matter. Plasmas have
unique physics compared to solids, liquids, and gases; although plasmas
are often treated as extremely hot gases, this is often incorrect.
Examples of plasmas include the sun, fluorescent light bulbs and other
gas-discharge tubes, very hot flames, much of interplanetary,
interstellar, and intergalactice space, the Earth's ionosphere, parts of
the atmosphere around lightning discharges, laser-produced plasmas and
plasmas produced for magnetic confinement fusion. Types of plasmas
include - Astrophysical, Collisionless, Cylindrical, Electrostatically
Neutral, Inhomogeneous, Intergalactic, Interstellar, Magnetized,
Nonneutral, Nonthermal, Partially Ionized, Relativistic, Solid State,
Strongly Coupled, Thermal, Unmagnetized, Vlasov and more."

A good definition from Gettysburg college:

http://www.gettysburg.edu/academics/physics/Plasma/Plasma2.htm

Or courtesy of the University of Texas at Dallas William B. Hanson
Center for Space Sciences:

http://utd500.utdallas.edu/~kivanc/index_fut.html#Plasma

Another defintion would be:
Plasmas are conductive assemblies of charged
particles, neutrals and fields that exhibit collective effects. Further, plasmas carry electrical currents and generate magnetic fields. Plasmas are the most common form of matter, comprising more than 99% of the visible universe.

But I like the defintion:
electromagnetic (Maxwell-Boltzmann)** systems
http://www.plasmas.org/basics.htm

Also disscused before:
https://www.physicsforums.com/archive/topic/t-59693_How_is_cold_Plasma_possible?.html

Then you should have noted the definition from the classic text in
electrodynamics by Jackson:

"An ionized gas should be called a plasma when the length scale which
separates short range and long range behavior is short compared to the
length scale of interest. Not all ionized gases are plasmas. For example,
a very dilute gas of a few moving charged particles, interacting pairwise,
is not a plasma. The conduction electrons in a metal are not a plasma,
either. It is not always easy to tell if something is a plasma, really.
Crudely, if you have to consider the inertial effects of the positive and
negative charge carriers in the dynamics (say, in response to an applied
electric field), then you've got a plasma."

It's when you get electrons with long mean free paths - like when the
gas is very hot - or the gas is very rarefied that you get a plasma.

The ionic solutions don't qualify on either count - they are more like
the conduction electrons in a metal.

When you study more advanced physics and learn about things like the
Debye length [ what the Debye length is in a plama, which is different
than the Debeye length in an electrolyte ] - you will better understand
your error.

Dr. Gregory Greenman
Physicist

 

[Davorak]

Ok I can except that I have the wrong definition.

Let me make sure I have this one right.

"An ionized gas should be called a plasma when the length scale which
separates short range and long range behavior is short compared to the
length scale of interest."

I translate this to good debye shielding.
{\lambda}_D\ll L
{N}_D\ggg 1

How is debye shielding different an ionic liquid does one of these fail?

"The conduction electrons in a metal are not a plasma,
either. It is not always easy to tell if something is a plasma, really.
Crudely, if you have to consider the inertial effects of the positive and
negative charge carriers in the dynamics (say, in response to an applied
electric field), then you've got a plasma."

This statement is self evident in meaning. I see how this fails for conduction elections in a metal, but I do not see this failing in an ionic solution. Since the charge carriers and neutrals can all be made a similar mass you would have to take them into account when applying an electric field.

Chen also gives the retraction of \omega \tau \gg 1. This also fails for a ionic solution.

"It's when you get electrons with long mean free paths - like when the
gas is very hot - or the gas is very rarefied that you get a plasma."

I thought counter example for this would be a super dense plasma say found in a star.

 

[Morbius]

How is debye shielding different an ionic liquid does one of these fail?

Davorak,

Because a plasma and an ionic liquid have different Debye lengths.

For a plasma:

{\lambda}_D = \sqrt{ {\epsilon_0 k T_e T_i} \over {n_e q_e^2 ( T_i + Z T_e) } }

whereas for an ionic liquid:

{\lambda}_D = \sqrt{{\epsilon_0 \epsilon_r k T} \over {2 N_A e^2 I}}

Additionally, you don't get the separation in temperatures in an ionic
solution that you get with a plasma. That's why the Debye formula
for the plasma has T_e[\itex] and T_i[\itex]; whereas the<br /> ionic solution has just T. You can't get separation of the electron and<br /> ion temperatures in an ionic solution, because the electrons are still<br /> bound.<br /> <br /> Dr. Gregory Greenman<br /> Physicist

 

[Davorak]

"Additionally, you don't get the separation in temperatures in an ionic
solution that you get with a plasma. That's why the Debye formula
for the plasma has T_e[\itex] and T_i[\itex]; whereas the<br /> ionic solution has just T. You can't get separation of the electron and<br /> ion temperatures in an ionic solution, because the electrons are still<br /> bound."<br /> Yes, but I did not think this separation was necessary for the definition of a plasma.<br /> <br /> What does I stand for in the ionic equation? I is usally current but that does not make sence.

 

[Davorak]

If the gas definition is absloute, does electricity flow(above break down voltage) through a liquid not count as plasma either? Is it given a different name?

 

[Morbius]

"Additionally, you don't get the separation in temperatures in an ionic
solution that you get with a plasma. That's why the Debye formula
for the plasma has T_e[\itex] and T_i[\itex]; whereas the<br /> ionic solution has just T. You can't get separation of the electron and<br /> ion temperatures in an ionic solution, because the electrons are still<br /> bound."<br /> Yes, but I did not think this separation was necessary for the definition of a plasma.<br /> <br /> What does I stand for in the ionic equation? I is usally current but that does not make sence.

<br /> <br /> Davorak,<br /> <br /> 'I' is the "ionic strength"<br /> <br /> Dr. Gregory Greenman<br /> Physicist

 

[Morbius]

If the gas definition is absloute, does electricity flow(above break down voltage) through a liquid not count as plasma either? Is it given a different name?

Davorak,

If you don't turn the liquid into an ionized gas - then no, it's not a plasma.

If you have a very substantial discharge, one that vaporizes and ionizes
the liquid, or maybe the electrodes - then you may have a plasma.

But just because you have the capability to conduct electricity - which
is well understood in ionic solutions - there was no reason to invoke this
phenomenon as a "fourth state of matter, being a plasma". Some of the
physics is very similar.

However, it's when you have the physics of the free electrons - with
large mean free paths - i.e. an independent "sea" of electrons - then you
have this fourth state of matter.

Dr. Gregory Greenman
Physicist

 

[CrazedMathematician]

Back on the topic of fusion...

Dr. Greenman,

I'm an undergrad in math, but one of my fascinations is with fusion, which I read as much as I can find on. I have a question regarding radiation losses in the plasma. From what I've read, one of the major losses is bremsstrahlung radiation caused by the braking of the ions by the electrons. Yet, every fusion device I've seen uses a neutral plasma. My question is, why isn't a nonneutral, pure ion plasma used for fusion? Without electrons, bremsstrahlung losses are eliminated. Sorry if the question is stupid or obvious, it's just been nagging me and I had to ask. :)

 

[Davorak]

A pure sea of ions will create one huge electric field it would rip away electrons from the nearest source. At least if you had a non trival number of ions.

The other problem would be how to remove the majority or all of the electrons in the first place.

 

[Morbius]

Back on the topic of fusion...

Dr. Greenman,

I'm an undergrad in math, but one of my fascinations is with fusion, which I read as much as I can find on. I have a question regarding radiation losses in the plasma. From what I've read, one of the major losses is bremsstrahlung radiation caused by the braking of the ions by the electrons. Yet, every fusion device I've seen uses a neutral plasma. My question is, why isn't a nonneutral, pure ion plasma used for fusion? Without electrons, bremsstrahlung losses are eliminated. Sorry if the question is stupid or obvious, it's just been nagging me and I had to ask. :)

CrazedMathematician,

As Davorak has already correctly pointed out - a pure ion plasma would
have a very high electric field, and there's the problem of how to make
that pure ion plasma.

Additionally, you think we've got problems now trying to confine an
electrically neutral plasma - it's going to be even tougher when you
have a plasma of particles that are all repelling each other without
any electrons to mitigate the repulsion.

Additionally, you don't eliminate bremstrahlung. You get bremstrahlung
any time you accelerate a charged particle. That is, any time, a charged
particle speeds up, slows down, or changes direction - it is accelerating -
and it will radiate. Unless you have a collisionless plasma - your ions
are going to be colliding.

You are going to get bremstrahlung losses due to ion-ion interactions.
Although in a neutral plasma, the electron-ion interactions are dominant,
the elimination of the electrons doesn't eliminate bremstrahlung - only
the dominant piece of it.

Dr. Gregory Greenman
Physicist

 

[sid_galt]

Does anybody know to what energy (in eVs) must a deuterium nucleus must be accelerated to achieve fusion with
1 - a tritium pellet in a cyclotron?
2 - a tritium nucleus which is not enclosed in a pellet assuming that the deuterium always hits the tritium nucleus so there is no need for high density?

 

[hitssquad]

Does anybody know to what energy (in eVs) must a deuterium nucleus must be accelerated to achieve fusion with [...] tritium [...]?

The resulting energy release is 17.6 MeV. This site says that that is an energy gain of 450 times, so perhaps the deuterium must be accelerated to .039 MeV. However, the Wiki article on fusion says the D-T ignition energy needed is 0.1 MeV:
http://en.wikipedia.org/wiki/Nuclear_fusion

 

[Astronuc]

The deuterium-tritium fusion reaction results in an energy gain of about 450:1!

Given the context of the site, it would seem that the deuteron and triton each have an energy, e.g. 0.039 MeV (~40 keV) as hitssquad mentioned.

However, the question is:

Does anybody know to what energy (in eVs) must a deuterium nucleus must be accelerated to achieve fusion with
1 - a tritium pellet in a cyclotron?
2 - a tritium nucleus which is not enclosed in a pellet assuming that the deuterium always hits the tritium nucleus so there is no need for high density?

Basically, both address the same question, i.e. what is the necessary energy for a deuteron to enable a fusion reaction with a stationary triton?

If one looks at the cross-section of a monoenergetic D beam on a tritiated target, the maximum cross-section occurs 110 keV. However, there is a probability of a fusion reaction at 15 keV, although the cross section is about 2 orders of magnitude lower.

Finally, I was looking at the formula for overcoming the coulomb barrier -

\large E_{CB}(MeV) = \Large \frac{1.44 Z_{1}Z_{2}}{1.16 \left ( A_{1}^{1/3} +<br /> A_{2}^{1/3} + 2 \right ) }

and with Z₁=Z₂=1, A₁=2, A₂=3
the number I get is approximately E_CB=0.264 MeV, which is higher than the energies stated above. I suspect that the equation may not be necessarily valid for light atoms, or due to QM, there is a probability that the reaction occurs at lower energies.

 

[sid_galt]

Thank you for the help.

I suspect that the equation may not be necessarily valid for light atoms, or due to QM, there is a probability that the reaction occurs at lower energies.

You mean barrier tunneling, right?

 

[NEOclassic]

The LANL "zipper" 14 MeV neutron source.

Does anybody know to what energy (in eVs) must a deuterium nucleus must be accelerated to achieve fusion with
1 - a tritium pellet in a cyclotron?
2 - a tritium nucleus which is not enclosed in a pellet assuming that the deuterium always hits the tritium nucleus so there is no need for high density?

Hi sid,
A few decades ago some fission bombs were so designed that they wouldn't suffer predetonation when iniated by a continuous externally sourced neutron stream. The so-called "zipper" had a triton beam that fell upon a deuterated target. The beam was accelerated by a 180,000 volt gradient. I realize that you seem to be concerned with pelletized tritium but the relative rare availability of tritons are better allocated when the deuterons are pelletized. Cheers, Jim

 

[CrazedMathematician]

As Davorak has already correctly pointed out - a pure ion plasma would
have a very high electric field, and there's the problem of how to make
that pure ion plasma.

Additionally, you think we've got problems now trying to confine an
electrically neutral plasma - it's going to be even tougher when you
have a plasma of particles that are all repelling each other without
any electrons to mitigate the repulsion.

Additionally, you don't eliminate bremstrahlung. You get bremstrahlung
any time you accelerate a charged particle. That is, any time, a charged
particle speeds up, slows down, or changes direction - it is accelerating -
and it will radiate. Unless you have a collisionless plasma - your ions
are going to be colliding.

You are going to get bremstrahlung losses due to ion-ion interactions.
Although in a neutral plasma, the electron-ion interactions are dominant,
the elimination of the electrons doesn't eliminate bremstrahlung - only
the dominant piece of it.

Dr. Gregory Greenman
Physicist

This paper I found talks about it, maybe you've read it:

Confinement Of Pure Ion Plasma In A Cylindrical Current Sheet
Plasma Physics Laboratory, Princeton University

http://www.osti.gov/bridge/servlets/purl/15113-w7GWk3/webviewable/15113.pdf

Abstract. A novel method for containing a pure ion plasma at thermonuclear densities and temperatures has been modeled. The method combines the confinement properties of a Penning-Malmberg trap and some aspects of the magnetic field geometry of a pulsed theta-pinch.

Introduction
This paper presents a novel method for achieving a well-known goal: the confinement of non-neutral ion plasmas that are adequately dense for controlled thermonuclear fusion applications.

Now most of the paper goes way over my head, so maybe you can explain the approach they're taking and if you think it's feasible.

 

[Morbius]

Now most of the paper goes way over my head, so maybe you can explain the approach they're taking and if you think it's feasible.

CrazedMathematician,

Interesting idea.

However, I note that this has only been modeled in 1-D.

In 1-D, you don't have the instabilities that break up the plasma. If you
think of a long "rope" of plasma - these instabilities manifest themselves
as "kinks" in the rope. Kinking of the rope is a 2-D or 3-D phenomenon
that isn't considered in their analysis.

Perhaps an actual experiment, as proposed by the paper; will decide if
it is a good idea or not.

Dr. Gregory Greenman
Physicist

 

[CrazedMathematician]

Dr. Greenman,

In your opinion, what is the most promising approach to fusion that will produce net energy? Also, do you think it's really worth it trying to induce fusion in commercially impractical fuels like Deuterium-Tritium or Deuterium-Deuterium, which produce high energy neutrons and, in the case of tritium, require a fission reactor to create the fuel? Shouldn't more effort be put into ways which could allow the fusion of aneuronic fuels like Helium 3-Deuterium, Helium 3-Helium 3, or Hydrogen-Boron 11? The latter of which is not only the most abundant (Hydrogen obviously, and Boron-11 makes up 80% of natural Boron) but also one of the safest and easiest to convert into electricity (directly using the charged particles). So while a device that would allow net energy production in a fuel like Tritium-Deuterium would be an incremental step, a device that could fusion Hydrogen-Boron 11 would be a giant leap, allowing nearly limitless amounts of electrical energy. What are your thoughts on this and the way fusion is being researched at the moment?

 

[hitssquad]

do you think it's really worth it trying to induce fusion in commercially impractical fuels like Deuterium-Tritium or Deuterium-Deuterium, which produce high energy neutrons and, in the case of tritium, require a fission reactor to create the fuel?

Those two issues are related. Fission reactors create tritium by bombarding lithium-6 with neutrons. Fusion reactors can make tritium in the same manner, and shield neutrons at the same time.

Also regarding fusion neutrons, some ideas for fusion reactors involve hybridization with fission such that fission fuel surrounds the fusion portion of the hybrid reactor reactor and uses the fusion-generated neutrons to produce controlled fission reactions. Similarly as above, this use of the fusion neutrons would simultaneously act as a shield.
http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fusion.html

--
The most promising source of tritium seems to be the breeding of tritium from lithium-6 by neutron bombardment with the reaction

{_3^6}Li + {_0^1}n \rightarrow {_2^4}He + {_1^3}H + 4.8 MeV

which can be achieved by slow neutrons. This would occur if lithium were used as the coolant and heat transfer medium around the reaction chamber of a fusion reactor.
--

 

[Astronuc]

You mean barrier tunneling, right?

Yes. When the minimum energy is less than the Coulomb 'barrier', it implies tunneling through the barrier.

 

[Morbius]

Dr. Greenman,

In your opinion, what is the most promising approach to fusion that will produce net energy?

CrazedMathematician,

Right now - I would say inertial confinement is the most promising.

Of course, since I work in the field - I'm an inertial confinement partisan.

Also, do you think it's really worth it trying to induce fusion in commercially impractical fuels like Deuterium-Tritium or Deuterium-Deuterium, which produce high energy neutrons

I see nothing commercially impractical about deuterium - especially
when compared to something like Helium-3. You are going to have to
go to the Moon to get large quantities of Helium-3.

Deuterium can be extracted from ocean water quite readily. About
1 in 140 atoms of Hydrogen in the ocean is Deuterium. Heavy water,
D20; is made on an industrial scale all the time.

The fast neutrons aren't a problem - in fact - that's where the ENERGY
is. Of the 17.6 MeV, that you get from D-T fusion; 14.1 MeV is in that
neutron.

Shielding for the neutrons and capturing their energy is NOT a big
problem. For example, LLNL proposed a concept in which the "first wall"
of an inertial confinement fusion reactor was a "shower" of liquid
lithium. The lithium shields the fast neutrons, captures their energy,
and breeds the needed Tritium.

and, in the case of tritium, require a fission reactor to create the fuel?

You don't need a fission reactor to create the Tritium - you can create
it from the neutrons from the D-T reaction.

Shouldn't more effort be put into ways which could allow the fusion of aneuronic fuels like Helium 3-Deuterium, Helium 3-Helium 3, or Hydrogen-Boron 11? The latter of which is not only the most abundant (Hydrogen obviously, and Boron-11 makes up 80% of natural Boron) but also one of the safest and easiest to convert into electricity (directly using the charged particles). So while a device that would allow net energy production in a fuel like Tritium-Deuterium would be an incremental step, a device that could fusion Hydrogen-Boron 11 would be a giant leap, allowing nearly limitless amounts of electrical energy. What are your thoughts on this and the way fusion is being researched at the moment?

For a whole host of reasons; I would put Helium-3 and Boron-11 fusion
on the absolute BOTTOM of my priority list. They look good if you
take a superficial look at them - but when you get into the real physics;
they're not all that promising and should be relagated to last place.

Dr. Gregory Greenman
Physicist

 

[sid_galt]

I have another question regarding d-t fusion in cyclotrons using external electric and magnetic fields.

Since around .264 MeV of energy per deuterium particle is required for d-t fusion, it means a particle has to be accelerated in around .264MV of voltage. So what inhibits the actual energy delivered to a particle to make such fusion costly?

 

[Morbius]

I have another question regarding d-t fusion in cyclotrons using external electric and magnetic fields.

Since around .264 MeV of energy per deuterium particle is required for d-t fusion, it means a particle has to be accelerated in around .264MV of voltage. So what inhibits the actual energy delivered to a particle to make such fusion costly?

sid_galt,

The energy you get out of the fusion doesn't pay for running the cyclotron.

If you want to get net energy out of fusion reactions - think of a fire.

An ordinary fire is self perpetuating - the energy needed to initiate the
next oxidation reaction comes from the oxidation reaction that has
just happened.

That's what you have to do with fusion - get the fusion reaction itself to
supply the energy needed to trigger the next fusion reaction.

In a cyclotron, you have to supply a lot of energy to the electromagnets
that keep the particles in their spiral orbits - energy which just goes
away as heat in the coils of the magnets.

You have to supply energy to the big RF oscillators that provide the
accelerating voltage on the cyclotron's "Dees". Again, that's energy
down the drain.

A cyclotron or any particle accelerator only accelerates a rather
small number of particles. You don't get moles and moles of particles
out of a cyclotron.

For the energy that you get out in the beam - the cyclotron, or any
other particle accelerator is very, very, inefficient. You can't throw
energy away like that - and get to breakeven - let alone a net power
production.

Cyclotrons and particle accelerators are research tools. Their basic
operating principles were not conceived to be efficient. They were
designed to get a small number of particles to study.

In order to have a fusion reactor that produces power; you need to fuse
macroscopic quantities of fuel. Cyclotrons are many, many, many,
orders of magnitude down in scale from what you need. Don't bother
with trying to base anything on cyclotron-induced fusion - that's a
dead end.

Dr. Gregory Greenman
Physicist

 

[CrazedMathematician]

Shielding for the neutrons and capturing their energy is NOT a big
problem. For example, LLNL proposed a concept in which the "first wall"
of an inertial confinement fusion reactor was a "shower" of liquid
lithium. The lithium shields the fast neutrons, captures their energy,
and breeds the needed Tritium.

But not ALL of the neutrons react with the lithium, some will smash into the reactor walls and make them radioactive. Obviously it doesn't produce nearly as much radioactive waste as fission but it still produces some.

For a whole host of reasons; I would put Helium-3 and Boron-11 fusion
on the absolute BOTTOM of my priority list. They look good if you
take a superficial look at them - but when you get into the real physics;
they're not all that promising and should be relagated to last place.

That's disappointing. Another major application of fusion is space travel. With fuels like Helium-3 and Boron-11 you can use the charged particles as thrust directly, allowing for extremely high specific impulses (over 1,000,000 seconds compared to 450 seconds for liquid oxygen and liquid hydrogen). With deuterium-tritium, since you can't use the neutrons directly for thrust, you would have to heat a working fluid which would significantly decrease your efficiency.

What do you think of this website:
http://www.focusfusion.org/
Is it for real? It talks about using a "plasma focus device for hydrogen-boron nuclear fusion".

 

[Morbius]

But not ALL of the neutrons react with the lithium, some will smash into the reactor walls and make them radioactive. Obviously it doesn't produce nearly as much radioactive waste as fission but it still produces some.

CrazedMathematician,

Is that a problem?

That's disappointing. Another major application of fusion is space travel. With fuels like Helium-3 and Boron-11 you can use the charged particles as thrust directly, allowing for extremely high specific impulses (over 1,000,000 seconds compared to 450 seconds for liquid oxygen and liquid hydrogen). With deuterium-tritium, since you can't use the neutrons directly for thrust, you would have to heat a working fluid which would significantly decrease your efficiency.

When I was in graduate school at MIT, we had one student that was
extolling the virtues of using tokamaks as space vehicle power plants.

So the professor put a problem on the final exam. He assumed a
2 Gigawatt tokamak; and made a lot of very optimistic assumptions -
and had us compute the thrust from diverting plasma out of the 2Gw
tokamak.

It turned out to be something like 2 Newtons of force.

"Plasma drive" turned out to be inefficient in the extreme.

Dr. Gregory Greenman
Physicist

 

[CrazedMathematician]

Is that a problem?

Are you trying to say that radioactive waste isn't a problem? If that was so then why bother with fusion at all, just use fission. We do have enough fuel for millions of years.

When I was in graduate school at MIT, we had one student that was
extolling the virtues of using tokamaks as space vehicle power plants.

So the professor put a problem on the final exam. He assumed a
2 Gigawatt tokamak; and made a lot of very optimistic assumptions -
and had us compute the thrust from diverting plasma out of the 2Gw
tokamak.

It turned out to be something like 2 Newtons of force.

"Plasma drive" turned out to be inefficient in the extreme.

Ummmm, I don't think you understand space propulsion. Efficiency is measured in specific impulse not thrust. So a thruster that has 2 GW output and 2 N of thrust is actually extremely efficient, with a specific impulse of about 200,000,000 seconds (which is not only about 2 orders of magnititude better than the best fusion reactions, it would also mean the exhaust velocity is 2 billion m/s, or faster than the speed of light which is obviously impossible, so your calculations are wrong). That is, one kg of fuel can provide one kg of thrust for 200 million seconds, or in this case, one kg of fuel can provide 2 N of force for 1 billion seconds. Yeah the thruster might only put out 2 N, but it can stay on for over 18,000 years on just 1 kg of fuel.

 

[Morbius]

Are you trying to say that radioactive waste isn't a problem? If that was so then why bother with fusion at all, just use fission. We do have enough fuel for millions of years.

Ummmm, I don't think you understand space propulsion.

WRONG! I know propulsion theory VERY WELL.

Efficiency is measured in specific impulse not thrust.

WRONG AGAIN - efficiency is efficiency and specific thrust is specific
thrust.

You can have a high specific thrust - however, in this case you
have an extremely low efficiency.

That is, an exceedingly small amount of the energy produced by
the tokamak went into propelling the craft.

Specific thrust is NOT efficiency - you can tell that right off the
bat by their dimensions.

Specific thrust has units of time [ seconds ] while
efficiency is dimensionless.

Yeah the thruster might only put out 2 N, but it can stay on for over 18,000 years on just 1 kg of fuel.

WRONG again - you didn't do the arithmetic.

1 kg of fusion fuel, at 2 GW of power will last you not quite 2 days.

Don't tell me that I don't know propulsion when you are just pulling
numbers out of the air.

Dr. Gregory Greenman
Physicist

 

[CrazedMathematician]

Power = 1/2 * Exhaust Velocity * Force

2000000000 watts = 1/2 * Ve * 2 N = Ve * 1 N
2000000000 watts / 1 N = Ve = 2000000000 m/s

Specific Impulse = Exhaust Velocity / Acceleration of Gravity
Isp = 2000000000 m/s / 9.8 m/s^2 = 204081632.6531 seconds

Now, if you're talking about efficiency in terms of Fusion Power Toward Thrust / Total Fusion Output Power (as I think you are) I'm wondering how you can truly speculate on the engineering details of a system in such an early stage. Are you saying that with all the future advances we won't improve efficiency? Is there some insurmountable barrier preventing us from getting higher efficiency like 50% or 75% or 99%? Seems very speculative.

 

[Morbius]

Power = 1/2 * Exhaust Velocity * Force

NO - the power that goes into driving the vehicle is equal to the
product of the force or thrust and the speed of the vehicle.

Your formula above is a limiting case.

2000000000 watts = 1/2 * Ve * 2 N = Ve * 1 N
2000000000 watts / 1 N = Ve = 2000000000 m/s

You've made the assumption above that ALL the energy of the 2 GW
tokamak goes into kinetic energy of the vehicle. This is not the case!

You are spewing some very hot plasma out the back of this vehicle - and
a miniscule portion of that is going into kinetic energy of the vehicle.

Specific Impulse = Exhaust Velocity / Acceleration of Gravity
Isp = 2000000000 m/s / 9.8 m/s^2 = 204081632.6531 seconds

Now, if you're talking about efficiency in terms of Fusion Power Toward Thrust / Total Fusion Output Power (as I think you are) I'm wondering how you can truly speculate on the engineering details of a system in such an early stage. Are you saying that with all the future advances we won't improve efficiency? Is there some insurmountable barrier preventing us from getting higher efficiency like 50% or 75% or 99%? Seems very speculative.

The way the MIT professor who wrote the exam problem posed it - he
made some very optimisitic assumptions about the details - what
fraction of the plasma could be diverted by diverters that were 100%
efficient at their function...

It's been a few decades since - so I don't recall all the specifics. However,
I do recall that the assumptions ranged from reasonable to optimistic.

This is a little like those problems you get in thermodynamics - the
specification of a power plant running on a Rankine cycle - with
14 stages of reheat, and extremely efficient turbines ... and with all
that - the efficiency is limited by the 2nd Law of Thermodynamics to
the limiting case of the Carnot efficiency. So you know - it doesn't
matter how advanced the heat engine - the Laws of Physics limit it to
the Carnot efficiency - and that's not speculative at all.

Dr. Gregory Greenman
Physicist