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US4058486A
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Producing X-rays
Assignee: Battelle Memorial Institute Inc
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Filing: 1972-12-29
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Granted: 1977-11-15
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Expires: 1992-12-29
Abstract
Abstract A method of producing X-rays by directing radiant energy from a laser onto a target. Conversion efficiency of at least about 3 percent is obtained by providing the radiant energy in a low-power precursor pulse of approximately uniform effective intensity focused onto the surface of the target for about 1 to 30 nanoseconds so as to generate an expanding unconfined coronal plasma having less than normal solid density throughout and comprising a low-density (underdense) region wherein the plasma frequency is less than the laser radiation frequency and a higher-density (overdense) region wherein the plasma frequency is greater than the laser radiation frequency and, about 1 to 30 nanoseconds after the precursor pulse strikes the target, a higher-power main pulse focused onto the plasma for about 10-3 to 30 nanoseconds and having such power density and total energy that the radiant energy is absorbed in the underdense region and conducted into the overdense region to heat it and thus to produce X-rays therefrom with the plasma remaining substantially below normal solid density and thus facilitating the substantial emission of X-rays in the form of spectral lines arising from nonequilibrium ionization states.
Inventors
- 👤 Philip J. Mallozzi
- 👤 Harold M. Epstein
- 👤 Richard G. Jung
- 👤 David C. Applebaum
- 👤 Barry P. Fairand
- 👤 William J. Gallagher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:45
CPC Classifications
H; H05; H05H; H05H6/00; G; G21; G21B; G21B1/00; G21B1/11; G21B1/23; G21G; G21G4/00; H01; H01S; H01S4/00; H05G; H05G2/00; H05G2/001; Y; Y02; Y02E; Y02E30/00; Y02E30/10
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
193 words
A method of producing X-rays that comprises directing radiant energy from a laser onto a target, wherein conversion efficiency of at least about 3 percent is obtained by providing the radiant energy in a low-power precursor pulse of approximately uniform effective intensity focused onto the surface of the target for about 1 to 30 nanoseconds so as to generate an expanding unconfined coronal plasma having less than normal solid density throughout and comprising a low-density (underdense) region wherein the plasma frequency is less than the laser radiation frequency and a higher-density (overdense) region wherein the plasma frequency is greater than the laser radiation frequency and, about 1 to 30 nonoseconds after the precursor pulse strikes the target, a higher-power main pulse focused onto the plasma for about 10 -3 to 30 nanoseconds and having such power density and total energy that the radiant energy is absorbed in the underdense region and conducted into the overdense region to heat it and thus to produce X-rays therefrom with the plasma remaining substantially below normal solid density and thus facilitating the substantial emission of X-rays in the form of spectral lines arising from nonequilibrium ionization states.
Claim 2
Independent Claim
193 words
A method of producing X-rays that comprises directing radiant energy from a laser onto a target, wherein conversion efficiency of at least about 3 percent is obtained by providing the radiant energy in a low-power precursor pulse of approximately uniform effective intensity focused onto the surface of the target for about 1 to 30 nanoseconds so as to generate an expanding unconfined coronal plasma having less than normal solid density throughout and comprising a low-density (underdense) region wherein the plasma frequency is less than the laser radiation frequency and a higher-density (overdense) region wherein the plasma frequency is greater than the laser radiation frequency and, about 1 to 30 nonoseconds after the precursor pulse strikes the target, a higher-power main pulse focused onto the plasma for about 10 -3 to 30 nanoseconds and having such power density and total energy that the radiant energy is absorbed in the underdense region and conducted into the overdense region to heat it and thus to produce X-rays therefrom with the plasma remaining substantially below normal solid density and thus facilitating the substantial emission of X-rays in the form of spectral lines arising from nonequilibrium ionization states.
Claim 3
Dependent Claim
20 words
A method as in claim 1, wherein the target consists essentially of an element having a high atomic number Z.
Claim 4
Dependent Claim
17 words
A material as in claim 1, wherein the element has an atomic number Z greater than 10.
Claim 5
Dependent Claim
21 words
A method as in claim 1, wherein the target consists essentially of iron, calcium, chromium, nickel, aluminum, lead, tungsten, or gold.
Claim 6
Dependent Claim
28 words
A method as in claim 1, wherein the amplitude, duration, and shape of the precursor pulse are adjusted to control the intensity and spectral content of the X-rays.
Claim 7
Dependent Claim
16 words
A method as in claim 1, wherein the precursor pulse comprises about 0.01 to 5 joules.
Claim 8
Dependent Claim
21 words
A method as in claim 1, wherein the precursor pulse comprises about 10 10 to 10 12 watts per square centimeter.
Claim 9
Dependent Claim
24 words
A method as in claim 1, wherein the precursor pulse strikes the target at an angle of about 20° to 70° from its surface.
Claim 10
Dependent Claim
16 words
A method as in claim 1, wherein the main pulse comprises at least about 0.1 joule.
Claim 11
Dependent Claim
22 words
A method as in claim 1, wherein the main pulse comprises about 10 to 200 joules in about 1 to 3 nanoseconds.
Claim 12
Dependent Claim
26 words
A method as in claim 1, wherein the target consists essentially of iron and the duration of the precursor pulse is about 8 to 10 nanoseconds.
Claim 13
Dependent Claim
27 words
A method as in claim 1, wherein the electron density in the low-density region of the plasma is about 10 16 to 10 21 per cubic centimeter.
Claim 14
Dependent Claim
27 words
A method as in claim 1, wherein the electron density in the higher-density region of the plasma is about 10 19 to 10 23 per cubic centimeter.
Claim 15
Dependent Claim
27 words
A method as in claim 1, wherein the radiant energy is focused onto a spot on the target having a diameter of about 10 to 1000 microns.
Claim 16
Dependent Claim
21 words
A method as in claim 1, wherein the volume of the plasma is about 10 -6 to 10 -3 cubic centimeter.
Claim 17
Dependent Claim
21 words
A method as in claim 1, wherein the thickness of the plasma in any direction is about 0.001 to 0.1 centimeter.
Claim 18
Dependent Claim
22 words
A method as in claim 1, wherein for low energy applications the X-rays are emitted predominantly in the form of spectral lines.
Claim 19
Dependent Claim
55 words
A method as in claim 1, wherein the radiant energy is focused onto a spot on the target having a diameter of about 10 to 100 microns, generating a plasma of about the same diameter, to form substantially a point source of X-rays and thus to provide substantially the advantages of stimulated emission of X-rays.
Claim 20
Dependent Claim
30 words
A method as in claim 1, wherein the composition of the target and the temperature of the plasma are selected to provide a substantial amount of stimulated emission of X-rays.
Claim 21
Dependent Claim
38 words
A method as in claim 1, wherein a substantial proportion of the X-rays produced are directed to impinge upon a fluorescent target so as to remove inner shell electrons from atoms thereof and thereby create a population inversion.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-11-14 | 1981-05-16 | 1981-11-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-11-14 | 1985-05-16 | 1985-11-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-11-14 | 1989-05-16 | 1989-11-15 | $7700.00 | Window Closed / Lapsed |