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X-RAY LASER
Plasma cylinder (red) created by the impact of a high power pulsed laser (blue). No mirrors are used, gain is achieved by amplified spontaneous emission and a beam emerges both in the forward and reverse directions. (Matthews and Rosen 1985, Lawrence Livermore National Laboratory)
The target is made of a thin foil of selenium or other element of high atomic number deposited on a vinyl substrate to give it rigidity. The target is irradiated from both sides with a pair of laser pulses from a high power pump laser whose focus is several hundred times longer than it is wide. When it strikes, the foil 'explodes' producing a plasma consisting of selenium ions stripped of 24 electrons. The resulting ion has a very high charge, the energy difference of the outer electrons scales as Z squared (Z=ion charge) this leads to very short wavelength x-ray transitions.
Since spontaneous decay rates scale as Z to the fourth power, the pump must supply 1,000 times as much energy and deliver it 10,000 times faster than an optical laser. The solution to this problem may be low Z-ions : It may not be necessary to strip away most of the electrons from a high atomic number element, less drastic means of x-ray lasing can be achieved by using other x-ray transitions such as core electrons, which are not shielded by the outer electrons and feel the full force of the nuclear charge. Also, promising results are obtained from strong x-ray transitions in core electrons of atomic microclusters (research by Rhodes et al., 1994)
Currently the efficiency of these laser schemes is very low because most are based on collisional excitation. Much higher efficiency can be achieved by rapid cooling, leading to three body recombination pumping of a highly ionized plasma. A hybrid scheme involving contact-cooling and adiabatic expansion seems to show the most promise.
There is another promising possibility based on Electromagnetically Induced Transparency (EIT) to dramatically reduce pump power requirements and obtain highly efficient Lasing Without Inversion (also known as phaseonium lasers or phasers).
PRACTICAL USES OF X-RAY LASERS
The following is a literature survey on the practical engineering applications of x-ray lasers.
The coherent ultra-short wavelengths would be the only practical way to manufacturing nanometer scale structures required in the fields of quantum-electronics and for construction of nanometer sized robots (nanides). These lasers could also be the only conceivable way to make holograms of complicated bio-molecules while they are still within a living cell. And the promise of x-ray lasers for inertial confinement fusion holds the promise of unlimited energy for humanity.
TRANSLATE INTO VIETNAMESE,THANKS
X-RAY LASER
Plasma cylinder (red) created by the impact of a high power pulsed laser (blue). No mirrors are used, gain is achieved by amplified spontaneous emission and a beam emerges both in the forward and reverse directions. (Matthews and Rosen 1985, Lawrence Livermore National Laboratory)
The target is made of a thin foil of selenium or other element of high atomic number deposited on a vinyl substrate to give it rigidity. The target is irradiated from both sides with a pair of laser pulses from a high power pump laser whose focus is several hundred times longer than it is wide. When it strikes, the foil 'explodes' producing a plasma consisting of selenium ions stripped of 24 electrons. The resulting ion has a very high charge, the energy difference of the outer electrons scales as Z squared (Z=ion charge) this leads to very short wavelength x-ray transitions.
Since spontaneous decay rates scale as Z to the fourth power, the pump must supply 1,000 times as much energy and deliver it 10,000 times faster than an optical laser. The solution to this problem may be low Z-ions : It may not be necessary to strip away most of the electrons from a high atomic number element, less drastic means of x-ray lasing can be achieved by using other x-ray transitions such as core electrons, which are not shielded by the outer electrons and feel the full force of the nuclear charge. Also, promising results are obtained from strong x-ray transitions in core electrons of atomic microclusters (research by Rhodes et al., 1994)
Currently the efficiency of these laser schemes is very low because most are based on collisional excitation. Much higher efficiency can be achieved by rapid cooling, leading to three body recombination pumping of a highly ionized plasma. A hybrid scheme involving contact-cooling and adiabatic expansion seems to show the most promise.
There is another promising possibility based on Electromagnetically Induced Transparency (EIT) to dramatically reduce pump power requirements and obtain highly efficient Lasing Without Inversion (also known as phaseonium lasers or phasers).
PRACTICAL USES OF X-RAY LASERS
The following is a literature survey on the practical engineering applications of x-ray lasers.
The coherent ultra-short wavelengths would be the only practical way to manufacturing nanometer scale structures required in the fields of quantum-electronics and for construction of nanometer sized robots (nanides). These lasers could also be the only conceivable way to make holograms of complicated bio-molecules while they are still within a living cell. And the promise of x-ray lasers for inertial confinement fusion holds the promise of unlimited energy for humanity.
