![]() ![]() X-radiation, discovered in 1895, was the key to understanding atomic arrangements in crystals.Instrum.12.1 A powder X-ray diffractometer 12 X-ray Diffraction and Mineral Analysis Smither, R., Abu Saleem, K., Beno, M., Kurtz, C., Khounsary, A., Abrosimov, N.: Diffraction efficiency and diffraction bandwidth of thermal gradient and composition gradient crystals, to be published in Rev. A 375, 408–412 (1996)Ībrosimov, N.V., Rossolenko, S.N., Thieme, W., Gerhardt, A., Schroder, W.: Czochralski growth of Si- and Ge-rich SiGe single crystals. et al.: On the feasibility of employing gradiënt kristal for high resolution synchrotron optics, Nucl. 37, 662 (2002)Ībrosimov, N.V., Rossolenko, S.N., Alex, V., Gerhardt, A., Schröder, W.: Single crystal growth of Si (1− x) Ge ( x) by the Czochralski technique. Malgrange, C.: X-Ray Propagation in distorted crystals: dynamical to kinematical theory. N., Malgrange, C.: Dynamical X-Ray propagation: a theoretical approach to the creation of new wave fields. Application to homogeneously bent crystals, J. Kato, N.: Pendellösung fringes in distorted crystals III. Kato, N.: Pendellösung fringes in distorted crystals II. Kato, N.: Pendellösung fringes in distorted crystals I. Penning P., Polder, D.: Anomalous transmission of X-Rays in elastically deformed crystals. et al.: Si 1− x Ge x gradient crystals: a new monochromator materiaal for hard X-rays. Thesis, Untersuchung von Si (1− x) Ge ( x)-Gradientenkristallen und in-situ getemperten Silizium-Einkristallen als Monochromatoren für hochenergetische Synchrotonstrahlung, Physics Department, University of Hamburg (1999) et al.: CLAIRE gamma-ray lens: flight and long distance test results. et al.: MAX – a gamma-ray lens for nuclear astrophysics. al.: Crystal diffraction lens telescope for focusing nuclear gamma rays. et al.: Review of crystal diffraction and its application to focusing energetic gamma rays. 4,429,411, Instrument and Method for Focusing X-Rays, Gamma-Rays and Neutrons' (1984) On Relativistic Astrophysics, Austin Texas, Dec. Smither, R.K.: Gamma Ray Telescope Using Variable-Metric Diffraction Crystals, 11th Texas Sym. Smither, R.K.: New Method for Focusing X-Rays and Gamma-Rays, Rev. On Future X-Ray Experiments in the 80's, GSFC, Oct. Smither, R.K.: Method for Focusing and Imaging X-Rays and Gamma-Rays with Diffraction Crystals, Sym. The use of this type of diffraction crystal is expected to increase the sensitivity of gamma ray telescopes by a factor of 5 over that possible with normal mosaic crystals. Experiments performed at 3 energies, 93 keV, 123 keV and 153 keV, with both the thermal gradient Si crystals and with the mechanically bent Si crystals, demonstrated that one can achieve diffraction efficiencies approaching 100% with moderate energy bandwidths (ΔE/E = 1.4%) and low atomic absorption (transmission = 0.65), in excellent agreement with theory. A series of experiments have been performed on all three types of crystals using high-energy x-ray beams from the Advanced Photon Source at the Argonne National Laboratory. Such curved planes can be obtained in 3 different ways, by using mixed crystals with a composition gradient, by applying a thermal gradient, and by mechanically bending a near perfect crystal. These crystals have near perfect crystal structure, but the crystalline planes are slightly curved. A recent breakthrough in our understanding of crystal diffraction for high-energy gamma rays has made it possible to develop crystals that have both high diffraction efficiency and a relatively broad energy bandwidth. With mosaic crystals there is a trade-off between bandwidth and diffraction efficiency – one can have either high efficiency or large bandwidth, but not both without losing too much intensity through atomic absorption. The crystals need to have both high diffraction efficiency and a relatively broad energy bandwidth. ![]() The approach in the MAX program is to use a crystal diffraction lens to collect photons over a large area and concentrate them on a small well-shielded detector, greatly improving the signal to noise ratio. To detect a reasonable number of supernovae, sensitivities of the order of a few times 10-7 γ cm-2sec-1 are needed – much better than possible with current instruments. A major goal of the MAX program is to detect and measure gamma rays produced following the nuclear reactions that take place in a supernova explosion. ![]()
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