what is self seeding?
One problem with SASE FELs is the lack of temporal coherence due to a noisy startup process. To avoid this, one can "seed" an FEL with a laser tuned to the resonance of the FEL.
Free-electron laser
One problem with SASE FELs is the lack of temporal coherence due to a noisy startup process. To avoid this, one can "seed" an FEL with a laser tuned to the resonance of the FEL. Such a temporally coherent seed can be produced by more conventional means, such as by high harmonic generation (HHG) using an optical laser pulse. This results in coherent amplification of the input signal; in effect, the output laser quality is characterized by the seed. While HHG seeds are available at wavelengths down to the extreme ultraviolet, seeding is not feasible at x-ray wavelengths due to the lack of conventional x-ray lasers.

a medium of free floating positive and negative charges is called a(n) Plasma what can you tell me about the physical properties of electron? The electric charge is negative one elementary charge; its mass is approximately 1/1836 that of the proton; exhibit properties of both particles and waves: they can collide with other particles and can be diffracted like light. where can you see its use? In the electron microscope; free-electron laser (FEL); cathode ray tubes; in welding;  Electron beam processing is used to irradiate materials in order to change their physical properties or sterilize medical and food products. were there any theories based on it? Yes - experiments by physicists Ernest Rutherford, Henry Moseley, James Franck and Gustav Hertz had largely established the structure of an atom as a dense nucleus of positive charge surrounded by lower-mass electrons. can you elaborate on the initial physicist's theory? He formulated the Rutherford model of the atom in 1911 that a very small charged nucleus, containing much of the atom's mass, was orbited by low-mass electrons. when was this formulated? 1911 what can you tell me about the second physicist? His contribution to physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number. This stemmed from his development of Moseley's law in X-ray spectra. what was his contribution on the study of atom? Moseley's discovery showed that atomic numbers were not arbitrarily assigned, but rather, they have a definite physical basis. Moseley postulated that each successive element has a nuclear charge exactly one unit greater than its predecessor. where was he born? Weymouth, Dorset in England what is fel ? A free-electron laser (FEL) is a synchrotron light source producing extremely brilliant and short pulses of synchrotron radiation.
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Free-electron laser [SEP] Self-seeding
One problem with SASE FELs is the lack of temporal coherence due to a noisy startup process. To avoid this, one can "seed" an FEL with a laser tuned to the resonance of the FEL. Such a temporally coherent seed can be produced by more conventional means, such as by high harmonic generation (HHG) using an optical laser pulse. This results in coherent amplification of the input signal; in effect, the output laser quality is characterized by the seed. While HHG seeds are available at wavelengths down to the extreme ultraviolet, seeding is not feasible at x-ray wavelengths due to the lack of conventional x-ray lasers.