Advertisement

High diffraction efficiency, broadband, diffraction crystals for use in crystal diffraction lenses

  • Robert K. Smither
  • Khaliefeh Abu Saleem
  • Dante E. Roa
  • Mark A. Beno
  • Peter Von Ballmoos
  • Gerry K. Skinner
Chapter

Abstract

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. 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. 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. The crystals need to 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. 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. These crystals have near perfect crystal structure, but the crystalline planes are slightly curved. 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. 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. 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. 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.

Keywords

Gamma-ray astronomy Crystal diffraction Thermal gradient Bent crystal 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Smither, R.K.: Method for Focusing and Imaging X-Rays and Gamma-Rays with Diffraction Crystals, Sym. On Future X-Ray Experiments in the 80’s, GSFC, Oct. 1981, NASA Tech. Mem. No. 83848 (1981)Google Scholar
  2. 2.
    Smither, R.K.: New Method for Focusing X-Rays and Gamma-Rays, Rev. Sci. Instrum. 44, 131–141 (1982)CrossRefADSGoogle Scholar
  3. 3.
    Smither, R.K.: Gamma Ray Telescope Using Variable-Metric Diffraction Crystals, 11th Texas Sym. On Relativistic Astrophysics, Austin Texas, Dec. 1982. Ann. of New York Acad. Sci. 44, 673 (1983)Google Scholar
  4. 4.
    Smither, R.K.: U.S. Patent No. 4,429,411, Instrument and Method for Focusing X-Rays, Gamma-Rays and Neutrons’ (1984)Google Scholar
  5. 5.
    Smither, R.K. et al.: Review of crystal diffraction and its application to focusing energetic gamma rays. Experimental Astronomy 6, 47–56 (1995)CrossRefADSGoogle Scholar
  6. 6.
    Smither, R. K. et. al.: Crystal diffraction lens telescope for focusing nuclear gamma rays. Proc. SPIE, 2806, 509 (1996)CrossRefADSGoogle Scholar
  7. 7.
    Ballmoos, P. von. et al.: MAX — a gamma-ray lens for nuclear astrophysics. Proc. SPIE 5168, 471 (2004)CrossRefADSGoogle Scholar
  8. 8.
    Halloin, H. et al.: CLAIRE gamma-ray lens: flight and long distance test results. Proc. SPIE 5168, 471 (2004)CrossRefADSGoogle Scholar
  9. 9.
    Keitel, S.: Ph.D. 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)Google Scholar
  10. 10.
    Keitel, S. et al.: Si1−x Gex gradient crystals: a new monochromator materiaal for hard X-rays. Nucl. Instrum. Methods Phys. Res. A 414, 427 (1998)Google Scholar
  11. 11.
    Penning P., Polder, D.: Anomalous transmission of X-Rays in elastically deformed crystals. Philips Res. Repts. 16, 419 (1961)Google Scholar
  12. 12.
    Kato, N.: Pendellösung fringes in distorted crystals I. Fermat’s principle for bloch waves. J. Phys. Soc. Japan 18, 1785 (1963)ADSCrossRefGoogle Scholar
  13. 13.
    Kato, N.: Pendellösung fringes in distorted crystals II. Application to two-beam cases. J. Phys. Soc. Japan 19, 67 (1964)ADSCrossRefGoogle Scholar
  14. 14.
    Kato, N.: Pendellösung fringes in distorted crystals III. Application to homogeneously bent crystals, J. Phys. Soc. Japan 19, 971 (1964)ADSCrossRefGoogle Scholar
  15. 15.
    Balibar, F., Chukhovskii, F. N., Malgrange, C.: Dynamical X-Ray propagation: a theoretical approach to the creation of new wave fields. Acta Cryst. A 39, 387 (1983)Google Scholar
  16. 16.
    Malgrange, C.: X-Ray Propagation in distorted crystals: dynamical to kinematical theory. Cryst. Res. Technol. 37, 662 (2002)CrossRefMathSciNetGoogle Scholar
  17. 17.
    Abrosimov, N.V., Rossolenko, S.N., Alex, V., Gerhardt, A., Schröder, W.: Single crystal growth of Si(1−x) Ge(x) by the Czochralski technique. Journal of Crystal Growth. 166, 657–662 (1996)CrossRefADSGoogle Scholar
  18. 18.
    Erko, A. et al.: On the feasibility of employing gradiënt kristal for high resolution synchrotron optics, Nucl. Instrum. Methods Phys. Res. A 375, 408–412 (1996)ADSGoogle Scholar
  19. 19.
    Abrosimov, N.V., Rossolenko, S.N., Thieme, W., Gerhardt, A., Schroder, W.: Czochralski growth of Si-and Ge-rich SiGe single crystals. Journal of Crystal Growth. 174, 182–186 (1997)CrossRefADSGoogle Scholar
  20. 20.
    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. Sci. Instrum. 79, 1 (2005)Google Scholar

Copyright information

© Springer 2006

Authors and Affiliations

  • Robert K. Smither
    • 1
  • Khaliefeh Abu Saleem
    • 1
  • Dante E. Roa
    • 1
  • Mark A. Beno
    • 1
  • Peter Von Ballmoos
    • 1
  • Gerry K. Skinner
    • 1
  1. 1.Argonne National laboratoryArgonne

Personalised recommendations