Coherent light generators – Short wavelength laser
Patent
1987-06-02
1989-10-17
Scott, Jr., Leon
Coherent light generators
Short wavelength laser
372 92, H01S 330
Patent
active
048752142
DESCRIPTION:
BRIEF SUMMARY
The principles of laser operation are well understood. The major difficulty in producing an X-ray laser is the extreme threshold power level needed. This threshold is proportional to the sixth power of frequency, so a 0.1 nanometer laser would require approximately 10.sup.21 watts to operate under the conditions of the original ruby lasers. This specification describes an apparatus which will attain X-ray laser conditions efficiently and at relatively low energy inputs.
For a given energy, power is increased by shortening the duty cycle. As threshold power is proportional to cavity volume and inversely proportional to the effective optical length of the cavity, a minimum cavity cross-section and maximum optical path length must be engineered. As the only practical method of producing inverted X-ray states is photo-ionisation, a discrete X-ray driving source must be provided. These criteria may all be satisfied by exploiting the violent collapse of a bubble.
The present device consists essentially of a bubble subject to violent collapse. The environment of the bubble is most likely to be liquid, but may be a colloid, suspension, slurry, gel, fluidised bed, solid or other medium which is or becomes fluent under impact, referred to herein generically as a fluent medium. The bubble shape is most likely to approximate a cylinder of high aspect ratio, i.e. a disc-like cylinder, though a range of other bubble shapes may provide advantages. The collapse will be precipitated by externally applied pressure though this could conceivably be the ambient pressure of the environment.
In the preferred embodiment, a bubble in liquid metal is used because the vapour pressure in the bubble can be very low, the ratio of specific heats for the vapour can be high, repeated collapse cycles can occur without chemical decomposition and careful alloying can provide a range of operational X-ray transitions. The bubble is essentially cylindrical with possibly a slight taper to encourage uni-directional emission. This configufation may be stably maintained by control of the liquid flow pattern during collapse. This control may be exercised by the profiles of the inner surface of the container, by inducing rotational or other non radial flow patterns or by inducing electric currents or magnetic fields. It is envisaged that rapid collapse will be induced by the application of very high external pressures. The more rapid the collapse, the more adiabatic the heating processes.
The mode of action is as follows. The collapse of the bubble can provide a very hot core either by adiabatic compression of the residual vapour within the bubble or by impact of opposing bubble walls at the instant of collapse. By appropriate selection of bubble dimensions, applied pressure, bubble vapour pressure and collapse geometry, it is possible to arrange that the core will have a very small cross section and will be hot enough to provide an intense thermal X-ray source for a short instant of time. The emitted X-rays will be absorbed in the cold bubble wall surrounding the hot core. The emitted radiation will propagate at the speed of light for a transparent core, whereas the energetic electrons associated with the heat wave will travel significantly more slowly and can be impeded by circulating currents in the liquid. Preferential photoionisation can therefore occur in the bubble wall and give rise to an inverted X-ray transition. The inversion may be dynamic or intrinsic to the transition if the ground state lifetime is significantgly less than the excited state lifetime. The high density of the bubble wall will ensure rapid absorption of the incident X-rays providing a small effective cavity volume. Calculation indicates that laser conditions may easily be attained.
Super-radiant emission can occur in the bubble wall and the gain will be greatest parallel to the surface. However, X-rays have a refractive index of less than one in matter, so the reduction in density toward the centre of the core will cause self focusing of the super-radiant beam along the a
REFERENCES:
patent: 3751666 (1973-08-01), Hug
patent: 3961197 (1976-06-01), Dawson
patent: 4252607 (1981-02-01), Thode
patent: 4263095 (1981-04-01), Thode
patent: 4611327 (1986-09-01), Clark et al.
Dahlbacka, R. et al., "Imploding Z Pinch X-Ray Laser" 2318B Applied Physics B. Photophysics and Laser Chemistry, vol. B28 (1982), June/July, No. 2/3, pp. 152-153.
Maxon, P. S., "A Gas Puff Soft X-Ray Laser Target Design", Journal of Applied Physics, 57, (1985), Feb. No. 3, pp. 971-972.
Hagelstein, P. L., "Review of Radiation Pumped Soft X-Ray Lasers", Plasma Physics, 25, (1983), Dec., No. 12, pp. 1345-1367.
Document from U.S. Department of the Navy, "Appendix 2/Current SDIO Objections", Comments on Proposal from Optical Research, Cambridge, U.K.
Jr. Leon Scott
O'Connell Robert F.
LandOfFree
X-ray laser does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with X-ray laser, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and X-ray laser will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1747887