Samonavigace laserových svazků na termonukleární pelety

1. Samonavigace laserových svazků na termonukleární pelety Lukáš Matěna

3. Hypotheticalinertialconfinementfusionpower plant • Sphericalevacuatedtargetchamber 10 m in diameter • Sphericalcryogenicfuelpelletisinjectedathigh speed • Thepelletisirradiated by laserswhen in the center ofthechamber and ignites • Releasedneutrons are absorbed in thewallsofthechamber and theheatisremoved by coolant • Thisall has to berepeatedfewtimes a second

4. Problemsofinertialfusion • Highrequirements on irradiationsymmetry • Insufficient laser repetitionrate • Very preciseinjectionsystemisneeded • Thetargetposition has to betracked in order to ensurerequiredirradiationprecition

5. Problems of inertial fusion • Highrequirements on irradiationsymmetry • Insufficient laser repetitionrate • Very preciseinjectionsystemisneeded • Thetargetposition has to betracked in order to ensurerequiredirradiationprecition Tracking the target and adjusting the optics for each shot might be possible, but also difficult to do, considering the precision needed is in the order of tens of micrometers. Alternative approach was therefore proposed.

6. Self-navigation method • Instead of tracking the target, the whole area in the middle of the target chamber is illuminated by low-energy laser light which reflects off the target • This light is collected, amplified and after a reflection on SBS phase conjugating mirror is sent back to the target and ignites it

7. Self-navigation method - stages

9. Proof of concept

10. Unconverted first harmonic removal • Because the higher harmonic conversion is never perfect, the unconverted first harmonic has to be filtered out • Possible way to do this is by Faraday rotator

11. Parameters of reflected light • Structure of amplitude on collecting windows is important in order to check whether the light can be properly amplified • It is important to realize, that light on a given window is in fact a superposition of light from many illuminating beams reflected off the target • A numerical simulation was developed to find out the parameters of reflected light

12. Numerical model • A random ray from the beam is selected, followed to the target and reflected • In case it hits the specified window, the distance travelled and polarization are calculated • The process is repeated until enough information is gathered

13. Wavefront shape after reflection

14. Phase and amplitude structure • Phase is easy to calculate from travelled distance • Amplitude is affected by the polarizer in the window • In case the beam is circularly polarized, the amplitude is the same for all the windows

15. Superposition from many beams • What needs to be calculated is amplitude structure after superposition of light from many beams • Considering the polarizers in the window, the superposition means only adding waves of the same frequency • However, a way to position arbitrary number of beams has to be found – another simulation was developed to accomplish this

16. Amplitude structure • 5 beams • 400 beams

17. Amplitude dependence on number of beams used

18. Conclusion • Amplitude after superposition varies rapidly across the window. A way to even the structure will probably have to be found. • So far only circular polarization was used. Linearly polarized light would make a difference. • Deviances from the ideal situation studied so far have to be considered.

19. Conclusion 2 • There is a lot of loose ends and matters that have not been studied so far (TDC and FR construction). • Even is self-navigation method worked, there are very serious issues with ICF itself (ignition not yet achieved, lasers, injection system), that might (and likely will) render the self-navigation method needless. • Magnetic confinement fusion (tokamaks) is more promising candidate for nuclear fusion power plant than ICF.