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An X-ray laser can be created by several methods either in hot, dense plasmas or as a free-electron laser in an accelerator. This article describes the x-ray lasers in plasmas, only.

The plasma x-ray lasers rely on stimulated emission to generate or amplify coherent, directional, high-brightness electromagnetic radiation in the near X-ray or extreme ultraviolet region of the spectrum, that is, usually from ~3 nanometers to several tens of nanometers (nm) wavelength.

Because of high gain in the lasing medium and short upper-state lifetimes (1–100 ps), X-ray lasers usually operate without mirrors; the beam of X-rays is generated by a single pass through the gain medium. The emitted radiation, based on amplified spontaneous emission, has relatively low spatial coherence. The line is mostly Doppler broadened, which depends on the ions' temperature.

As the common visible-light laser transitions between electronic or vibrational states correspond to energies up to only about 10 eV, different active media are needed for X-ray lasers.

Between 1978 and 1988 in Project Excalibur the U.S. military attempted to develop a nuclear explosion-pumped X-ray laser for ballistic missile defense as part of the "Star Wars" Strategic Defense Initiative (SDI).[1]

Active media

The most often used media include highly ionized plasmas, created in a capillary discharge or when a linearly focused optical pulse hits a solid target. In accordance with the Saha ionization equation, the most stable electron configurations are neon-like with 10 electrons remaining and nickel-like with 28 electrons remaining. The electron transitions in highly ionized plasmas usually correspond to energies on the order of hundreds of electron volts (eV).

The vacuum chambers at the PALS laboratory in Prague, where a 1 kJ pulse creates plasma for X-ray generation

Common methods for creating plasma X-ray lasers include:

An alternative amplifying medium is the relativistic electron beam in a free-electron laser, which, strictly speaking, uses stimulated Compton scattering instead of stimulated emission.

Other approaches to optically induced coherent X-ray generation are:


Applications of coherent X-ray radiation include coherent diffraction imaging, research into dense plasmas (not transparent to visible radiation), X-ray microscopy, phase-resolved medical imaging, material surface research, and weaponry.

A soft x-ray laser can perform ablative laser propulsion.

See also


  1. ^ Retrieved 2023-11-02. ((cite web)): Missing or empty |title= (help)
  2. ^ Rocca, J. J.; Shlyaptsev, V.; Tomasel, F. G.; Cortázar, O. D.; Hartshorn, D.; Chilla, J. L. A. (1994-10-17). "Demonstration of a Discharge Pumped Table-Top Soft-X-Ray Laser". Physical Review Letters. 73 (16): 2192–2195. doi:10.1103/PhysRevLett.73.2192. hdl:10217/67823.
  3. ^ Kuba, Jaroslav. Experimental and Theoretical Study of X-ray Lasers Pumped by an Ultra-Short Laser Pulse: Transient Pumping of Ni-like Ag Ions. Université de Paris, France 2001.
  4. ^ Chang, Zenghu; Rundquist, Andy; Wang, Haiwen; Murnane, Margaret M.; Kapteyn, Henry C. (20 October 1997). "Generation of Coherent Soft X Rays at 2.7 nm Using High Harmonics". Physical Review Letters. 79 (16): 2967. Bibcode:1997PhRvL..79.2967C. doi:10.1103/PhysRevLett.79.2967.
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  7. ^ Whittum, David H.; Sessler, Andrew M.; Dawson, John M. (1990). "Ion-channel laser". Physical Review Letters. 64 (21): 2511–2514. Bibcode:1990PhRvL..64.2511W. doi:10.1103/PhysRevLett.64.2511. PMID 10041731.