I'm not up to date on the conductivity of CNTs. Do you have some links?IntLibber wrote:Note that carbon nanotubes are a practical room temp superconductor. Not a superconductor on the lines of zero resistance, but in terms of many times more amp capacity than copper, silver, or gold (superconductors tend to have rather inflexible catastrophic current limits). It can exhibit metallic or semiconductor behavior depending on the number of rings around the loop. Given the thermal tolerance as well, IMHO they should be making their plans for magnets out of nantube wire.MSimon wrote:The Carbon-Carbon bond is 12 eV. Let us assume for the sake of argument that the Graphene bond is 10X that - 120 eV.arclein wrote:We are just starting to learn how to use graphene. That would eliminate the obvous problems around conventional conductors.
I am expecting this tech to be advanced very rapidly. It starts by been stronger that diamond.
The pulesd energy involved is at minimum 10KV at mega Amps. There will be serious electrode erosion. Even if the electrode can be reformed quickly there will be the problems of contamination of the insulators and the reactor vessel.
comp?
Engineering is the art of making what you want from what you can get at a profit.
http://en.wikipedia.org/wiki/Carbon_nanotube#ElectricalMSimon wrote:
I'm not up to date on the conductivity of CNTs. Do you have some links?
"Because of the symmetry and unique electronic structure of graphene, the structure of a nanotube strongly affects its electrical properties. For a given (n,m) nanotube, if n = m, the nanotube is metallic; if n − m is a multiple of 3, then the nanotube is semiconducting with a very small band gap, otherwise the nanotube is a moderate semiconductor. Thus all armchair (n=m) nanotubes are metallic, and nanotubes (5,0), (6,4), (9,1), etc. are semiconducting. In theory, metallic nanotubes can have an electrical current density more than 1,000 times greater than metals such as silver and copper."
http://www.pa.msu.edu/cmp/csc/ntproperties/
"Resistivity and Maximum Current Density
Relatively early in the research of nanotubes, Thess et al. calculated the resistivity of ropes of metallic SWNTs to be in the order of 10-4 -cm at 300 K. [2] They did this by measuring the resistivity directly with a four-point technique. One of their values they measured was 0.34 x 10-4, which they noted would indicate that the ropes were the most highly conductive carbon fibers known, even factoring in their error in measurement. In the same study his measurements of the conductivity, Frank et al. [5] was able to have reach a current denisty in the tube greater than 10^7 A/cm2. Later, Phaedon Avouris [12] suggested that stable current densities of nanotubes could be pushed as high as 10^13 A/cm2. "
10,000,000 to 10,000,000,000,000 Amps per square CM of conductor cross section? Dude....
Imagine the field densities that could be attained in a polywell with electromagnets made from conductors like that?
Copper bus bar is rated at 4 A/ sq mm. Which is 400 A/sq cm. Of course if you are willing to let the bus bar run very hot you might get up to 10X that.
So 4,000 A/sq cm might be around the ultimate current. In round numbers - on the order of 10,000 A/sq cm.
Just as a point of reference.
Also the resistivity is about 1/5th that of copper. Good - but not spectacular. Which means the coils would have to run hot for really high currents - the losses would mount rapidly.
Blogged at:
http://iecfusiontech.blogspot.com/2009/ ... ctors.html
and
http://powerandcontrol.blogspot.com/200 ... ctors.html
So 4,000 A/sq cm might be around the ultimate current. In round numbers - on the order of 10,000 A/sq cm.
Just as a point of reference.
Also the resistivity is about 1/5th that of copper. Good - but not spectacular. Which means the coils would have to run hot for really high currents - the losses would mount rapidly.
Blogged at:
http://iecfusiontech.blogspot.com/2009/ ... ctors.html
and
http://powerandcontrol.blogspot.com/200 ... ctors.html
Last edited by MSimon on Mon Jan 12, 2009 9:41 pm, edited 1 time in total.
Engineering is the art of making what you want from what you can get at a profit.
Ya. Either way, I think given CNT's thermal conductivity properties along with its electrical properties make for a superior conductor compared to those superconductors that need liquid nitrogen or CO2, given the immense amount of heat coming from the fusion reaction, I think a conductor a bit less likely to fail catastrophically would be in order. When a superconductor with a sharp temperature threshold fails, it tends to do so rather explosively. Not a good design feature in a reactor that creates a lot of heat.MSimon wrote:Copper bus bar is rated at 4 A/ sq mm. Which is 400 A/sq cm. Of course if you are willing to let the bus bar run very hot you might get up to 10X that.
So 4,000 A/sq cm might be around the ultimate current. In round numbers - on the order of 10,000 A/sq cm.
Just as a point of reference.
CNT allows for water cooling and a more forgiving design.
The current density is high but the resistivity is only 1/5th that of copper - a help but not a huge break through. See revisions to my previous comment.IntLibber wrote:Ya. Either way, I think given CNT's thermal conductivity properties along with its electrical properties make for a superior conductor compared to those superconductors that need liquid nitrogen or CO2, given the immense amount of heat coming from the fusion reaction, I think a conductor a bit less likely to fail catastrophically would be in order. When a superconductor with a sharp temperature threshold fails, it tends to do so rather explosively. Not a good design feature in a reactor that creates a lot of heat.MSimon wrote:Copper bus bar is rated at 4 A/ sq mm. Which is 400 A/sq cm. Of course if you are willing to let the bus bar run very hot you might get up to 10X that.
So 4,000 A/sq cm might be around the ultimate current. In round numbers - on the order of 10,000 A/sq cm.
Just as a point of reference.
CNT allows for water cooling and a more forgiving design.
I think we are stuck with superconductors for high field work. For now.
Engineering is the art of making what you want from what you can get at a profit.
I read through Art's exchange with Lerner a while back. I have to side with Art on that, 100%.
I never got the impression he was even interested in a technical discussion. Lerner was eventually banned from editing Wikipedia, and fairly I think.
I don't think he's as bad as the "Free Electricity" Sonship guys with their "quantum effects" from permanent magnets (not to mention the infamous laundry ball), but he seems more interested in funding than theory.
I never got the impression he was even interested in a technical discussion. Lerner was eventually banned from editing Wikipedia, and fairly I think.
I don't think he's as bad as the "Free Electricity" Sonship guys with their "quantum effects" from permanent magnets (not to mention the infamous laundry ball), but he seems more interested in funding than theory.
Tom Ligon
Hey, you could retro fit your Pinto and stop worrying about blowing up the gas tank.Ford makes the Focus.
Ford makes the Fusion.
Suppose Ford built miniature plasmoid generators the general size of spark plugs, capable of p-B11 fusion, and built the Focus Fusion, using a piston engine driven by little fusion pops?
Burning question: if Lerner is so allegedly brilliant, why is he spending time at Wikipedia arguing with his (supposed) intellectual inferiors?TallDave wrote:I never got the impression he was even interested in a technical discussion. Lerner was eventually banned from editing Wikipedia, and fairly I think.