Bald ZETTAWATTS und vielech YOTTAWATT lasers!

[rocketman340]

Hallo,
ich habe heute erfahren, dass die wissenschaftliche Gemeinschaft, die mit künftigen Programmen über den Bau der Hochleistungslaser verwended für Kernfusion ein großes Problem zu lösen hatte.

Bis jetzt das Problem liegt in der Spitzenleistung des Lasern begrenzt ist,nach die verdichtung des Laserpulses (Stretching).
Die maximale Energie auf das Gitter erlaubt ist, ist in der Größenordnung von 0,4 J/cm2 in 25 fs.
Das will sagen, das ein ZETTAWATT laser in 25 femtosecunden ein gitter spiegel von 1000 m2 brauchte was unrealistsch ist und nicht zahlbare ist(ein gitter von 1m2 costet uber 1Millionen euro)

Plasma relastivic spiegel konnen 10 kJ/cm2 ruckstreuen das ist 0.25 m2 und costet nicht's !
Und wenn der spiegel nach licht geswindikeit gegen der laser beam kommt wird der pulse noch comprimiert!
die ersten Messungen an relastivic Spiegeln zeigten, dass eine Stärke von 10 kJ/cm2 möglich ist.
Welche ermöglicht niedrigere Kosten Lasern und sogar ZETTAWATTS und sparter YOTTAWATTS zu realisieren!
Das Verfahren wird durch Resonanzverstärkung der Impuls durch Raman-Rückstreuung Plasma genannt.
Ich habe eine kleine presentation of YOUTUBE gemacht
sagen Sie mir was sie denken?
sorry fur mein Deutsch! fur mich ist besser in English .
http://www.youtube.com/watch?v=SK2OZXvR37c

[VDX]

... to avoid misinterpretations you can post the English version too ...

Viktor

[rocketman340]

... to avoid misinterpretations you can post the English version too ...

Viktor

The idea of the C3 method is to separate the process of compression into three stages, including the CPA, OPCPA and compression based on the backward Raman scattering. To illustrate this concept, let us take as an example a laser system at LIL in the center of CEA (France), consisting of eight beams, each having an energy of 10 kJ, duration of 5 ns and a wavelength of 1050nm. Due to a small frequency modulation with a shift Δt = 1 / (20 ps) compression may be made up to about 20 ps.
At the first stage of compression, the CPA technique, aimed at transforming the initial pulses into pulses with 10 kJ energies and 20 ps durations, implies a sufficiently narrowband signal at the output. Therefore, dielectric diffraction gratings may be employed for this purpose instead of metal-coated gratings. The dielectric gratings have three important advantages.

First, for a narrow-band signal, they have high efficiency of about 99%.

Second, the breakdown threshold for the dielectric used for the 20 ps duration is at the level of 5 J/cm2, whereas for the metal-coated gratings it is only about 0.1 J/cm2 for 10-20 fs.

Third, such gratings are commercially available with an area of 1 m2.

At this intermediate step, gratings with an area of about 0.2 m2 only will be needed for operating 10 kJ beams.
At the second stage, by using the OPCPA technique it is expected to generate a Powerful femtosecond pulse at a wavelength of 1250 nm, which later (at the third stage) will be used as a seed pulse for the Raman compression. A relatively high intensity and quality of the generated pulse, as well as small prepulse provided by this technique are of importance because at the third stage the seed pulse must be repeatedly amplified, competing with a number of undesirable effects: the backward Raman scattering (BRS), due to scattering of Langmuir waves along the path of pump pulse propagation before interaction with the main seed pulse , the depletion of the pump pulse due to prepulse amplification , scattering by plasma inhomogeneities , and resonant sidescattering caused by large values of transverse scales . The influence of these negative processes can be significantly reduced by introducing a plasma density gradient and a corresponding linear frequency modulation in the pump pulse.
Note that this idea can be realized also for several pump pulses matched appropriately . In case of suppression by one or another way of all the above effects, the seed pulse will be resonantly amplified, absorbing much of the pump energy. In general, this can be achieved because all the unwanted effects are usually more sensitive to frequency detuning than the process of amplification of the seed pulse. The OPCPA method is perfectly suitable for generation of the seed pulse required at this stage. At the IAP RAS the possibility of obtaining pulses with energy of 50 J and duration of 20 fs withan adjustable wavelength of 1250 nm has been demonstrated at the PEARL facility.
At the third stage, it is suggested to use the effect of backward Raman scattering to compress the pulse obtained by the CPA technique from 20 ps to 10 fs. This effect leads to increased radiation with a frequency equal to the difference between the pump frequency and the plasma frequency. For the condition of resonance amplification of the seed with a wavelength of 1250 nm all pump pulses with a wavelength of 1050 nm will require plasma with concentration of 10^19 cm-3 and the size of the interaction region of about 3 mm. The peak intensity after amplification is limited by the manifestation ofrelativistic effects at the level of 10^17 W/cm2, which corresponds to the transverse diameter of the interaction region of about 3 cm for a pump energy of 10 kJ. Note that in comparison with the crystal the plasma as an amplifying medium is less sensitive to the directions of the pump pulse because of the lack of any selected axes, and therefore allows the use of multiple pump pulses. On the other hand, various nonlinear effects occurring in plasma during the amplification process at high intensities may reduce the efficiency. However, as is shown by numerical experiments with the PIC method, the seed pulse under certain conditions may be quite stably amplified to the intensities of the order of 4 × 10^17 W/cm2with the efficiency of energy transfer from the pump of about 50%.
It should be noted that the idea of Raman amplification of laser pulses is being developed in a number of other experimental teams. In particular, besides the abovementionedlaser facility at LIL, France, experiments on Raman amplification are being planned at the Trident facility, Los Alamos National laboratory, USA. At this facility, experiments on the combined stimulated Raman scattering have been already performed (jointly with the LULI, France.
Very interesting this C3 method!

[VDX]

... interessanter Ansatz - läßt mich sofort an die wilden(?) Theorien zu 'Hinter-Horizont'-Aktionen mit den in der Stratosphäre oder Ionosphäre mit HAARP erzeugten 'Plasma-Hohlspiegeln' denken, über die dann Mikrowellen mit hoher Energie auf Ziele am/im Boden oder unter Wasser fokussiert werden sollte

Der gleiche Ansatz sollte doch auch mit niedrigeren Energien und mit z.B. per Ultraschall oder Laser virtuell erzeugten Dichte-Gradienten oder 'Kavitations-Optiken' in Wasser denken, mit denen dann wiederum Ultraschall oder Laser fokussiert werden kann ...

Viktor

[rocketman340]

... interessanter Ansatz - läßt mich sofort an die wilden(?) Theorien zu 'Hinter-Horizont'-Aktionen mit den in der Stratosphäre oder Ionosphäre mit HAARP erzeugten 'Plasma-Hohlspiegeln' denken, über die dann Mikrowellen mit hoher Energie auf Ziele am/im Boden oder unter Wasser fokussiert werden sollte

Der gleiche Ansatz sollte doch auch mit niedrigeren Energien und mit z.B. per Ultraschall oder Laser virtuell erzeugten Dichte-Gradienten oder 'Kavitations-Optiken' in Wasser denken, mit denen dann wiederum Ultraschall oder Laser fokussiert werden kann ...

Viktor

Hallo Viktor,

The SBS ( Simulated Brillouin Scattering) is a third order effect that occurs as amplified spontaneous Brillouin scattering at sufficiently high intensities of the incident light wave, wich increase the sound wave amplitude by electrostriction ( show my video http://www.youtube.com/watch?v=Wstf71SKMl0 )
It occurs also as spontaneous scattering, in the nonresonant spectral range.
But SBS is an inelastic optical scattering process with very small energy loss, as it excites an acoustic phonon of the hyper-sound wave

SBS is applied in phase conjugating mirrors (PCM) for improvement of the beam quality in high power solid state laser amplificator. Later i will show this effect on a video.
rocketman340