High power femto- and picosecond pulses can generate filaments in air at atmospheric pressure. The filament is basically a plasma column which exists for about 130ns after the short pulse (0.5-2ps) arrives. One laser (for instance Trumpf Dira or Amphos 3706 or maybe even NKT/Onefive Origami) can repeatedly generate a filament on the repetition rate frequency. At about 8kHz the plasma column exists quasi continuously.
For fusion to happen one needs plasma at high enough density for long enough time.
1) We are not limited on time if the plasma column exists continuously.
2) Also the electron (ion) density of the filament in air was measured to be about 10^16-10^17 cm-1 so we don't have a low density either.
Wouldn't a filament in deuterium-tricium gas create fusion? I can't find any experiments exploring this direction.
What am I missing? Would this be possible? Maybe I just take the Lawson's criterion too simplified.
I would surely try it if I had access to a high power laser system like this.. xD
Hmm, the temperature doesn't seem to be high enough, it's only 3000-5000K.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.osapublishing.org/oe/viewmedia.cfm%3Furi%3Doe-26-22-29110%26seq%3D0%23:~:text%3DElectron%2520temperatures%2520are%2520determined%2520to,incident%2520laser%2520energy%2520or%2520wavelength.&ved=2ahUKEwjN7KKAx4jzAhUOh_0HHbKaCL4QFnoECAQQBg&usg=AOvVaw0QUoR32vsEUBexeFTKvUk7&cshid=1631969216133
The patricles need more kinetic energy to fuse. I wonder how the kinetic energy could be increased to make them fuse..
Really nice Daniel!! Thanks for your answer!!
Instead of going for a MHz 100mJ laser, there must be a trick like 1) using more lasers and 2) doing a ring "filament waveguide".
Do you know a way to bend the laser filament? I wonder if the filament is a ring, will it guide the light pulses which are coupled in tangentially?
One pulse can create a very long filament so once you have the pulses circling around in the ring, they would create a much longer lasting plasma. Let's say a 100mJ laser at 1kHz repetition rate can create a 10 km long straight filament. In a 10m circumference circle it would create filaments 1000 times before fading away. That's equivalent to a 100mJ 1MHz laser. Take 10 such laser and you have 10MHz so a continous filament.
Maybe putting the filament in a rotating magnetic field would form a ring like in some ion storage devices. Let me know your thoughts!
Best regards,
Daniel
Oh I posted the question about 2-3month ago. 16th of September I believe. ;)
I had a quick look at the paper you linked, the 720mJ is wild but only 80m filamentation? I seem to remember that the teramobile project achieved kilometers long filamentation with just half as much pulse energy. I will read it properly anyway, appreciated!
Bending of the filament seems to be possible but so far I haven't seen serious bending angles.. Let me see if I can find some related papers
So creating a "curved" filamentation is possible using an Airy beam:
https://patents.google.com/patent/US9757815B2/en
In worst case one could create a loop with multiple lasers in a polygon-formation and coupling the energy from one to another with rather poor efficiency..
Article Energy transfer between few-cycle laser filaments in air
The problem is as you described earlier that creating the plasma needs a lot of energy. In Article Ultrafast thin-disk multipass amplifier with 720 mJ operatin...
720mJ 1ps creates 70m long plasma - this is ca. 10mJ/m. The teramobile project had 600m using 350mJ but much shorter pulses at 10Hz.If the pulses are going around in a 1m circumference circle, having only 1% loss per loop, 10mJ/m is needed every 100ns (lifetime of the plasma) to maintain a quasi-continuous ionization. This would require 1000 pieces of these fine 720mJ 1kHz lasers..
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