X-ray or gamma ray systems or devices – Source
Patent
1994-02-04
1995-12-05
Porta, David P.
X-ray or gamma ray systems or devices
Source
378121, 378137, 378138, H01J 3530
Patent
active
054736617
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention starts from an apparatus for the production of short-wave electromagnetic radiation, especially in the x-ray and gamma-ray region, by means of the interaction between accelerated charged particles, especially electrons or positrons, and a crystal lattice, with a charged-particle source for the production of a beam of energetic charged particles and with a crystal arrangement which is so arranged in the path of the charged particle radiation beam that the charged particles traverse the crystal lattice of the crystal arrangement parallel to a predetermined lattice direction ("channeling-condition").
Energetic charged particles, which impinge upon a suitable single crystal at an angle to a crystal plane or a crystal axis which is sufficiently small, are moved in an oscillatory fashion lengthwise of the pertinent crystal direction along the crystal plane or crystal axis, respectively, (so-called channeling or canalization) and emit therewith electromagnetic radiation in the forward direction, the energy whereof lies in the x-ray or gamma-radiation region, assuming corresponding mass and energy of the incident charged particles (so-called channeling- or canalization-radiation). For example, electrons with an energy between 20 and 100 MeV produce x-rays with energies between about 20 and 200 keV in monocrystalline silicon.
In the usual apparatus for the production of canalization-radiation a charged particle radiation of the smallest possible divergence is used, which impinges upon a flat single crystal parallel to a selected crystal plane or crystal axis, respectively (Appl. Phys. Lett. 57 (27), Dec. 31, 1990, 2956-2958).
In the known apparatus of the aforementioned type, therefore, the most parallel charged particle radiation possible is used, and there arises an essentially parallel beam of electromagnetic radiation. For many applications, however, appreciably convergent or divergent beams of shortwave electromagnetic radiation are required. This creates problems, since no focusing optical elements, such as lenses, are available for short-wave electromagnetic radiation.
SUMMARY OF THE INVENTION
The present invention is based upon the task of further developing an apparatus of the aforementioned type in such a way that with it a non-parallel, and thus convergent or divergent, beam of short-wave electromagnetic radiation, especially in the x-ray and gamma-ray region, can be produced.
This task solved by means of an apparatus for the production of short-wave electromagnetic radiaion, especially in the x-ray and gamma-ray region, by means of the interaction between accelerated charged particles, especially electrons or positrons, and a crystal lattice, with a charged-particle source for the production of a beam of energetic charged particles and with a crystal arrangement which is so arranged in the path of the charged particle radiation beam that the charged particles traverse the crystal lattice of the crystal arrangement parallel to a predetermined lattice direction (lattice plane, lattice axis) ("channeling-condition"), which is characterized in that the crystal arrangment is traversed by the charged particles in at least one plane passing through the axis of the charged particle radiation beam in directions which essentially converge into a predetermined point, and in that the crystal arrangement is so arranged in an arc about the predetermined point, that the channeling condition is substantially fulfilled for all charged particle beam paths.
The apparatus according to the invention makes it possible to create a non-parallel beam of short-wave electromagnetic radiation, especially in the x-ray and gamma-ray region, with predetermined convergent- or divergent properties, since the convergence or divergence, respectively, of the short-wave electromagnetic radiation is determined by the convergence or divergence, respectively, of the charged particle radiation beam which impinges on the crystal arrangement; and the latter can easily be influenced by particl
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Rev. Sci. Instrum. 58 No. 7, Jul. 1987, pp. 1173-1176, Henins, "Variable ius Curved Crystal Mount".
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Applied Physics Letters, Bd. 57, Nr. 27, 31. Dec. 1990, P.2956-2958; Genz et al: "High Intensity Electron Channeling And Perspectives For A Bright Tunable X-Ray Source".
Soviet Journal of Quantum Electronics. B.11. Nr.11.1. Nov. 1981, P.1405-1421; Kalashnikov et al, "Spontaneous and Stimulated Gamma Radiation Emitted by Relativistic Charged Channeled Particles (Review)".
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Kalinin, et al, "Automatic Orientation System For Single-Crystal Targets In An Electron Accelerator".
Max-Planck-Gesellschaft zur Forderung der Wissenschaften e.V. Be
Porta David P.
Wong Don
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