Optical constants in the hard x-ray/soft gamma-ray range

Direct measurement of the amount of Pu and U in spent nuclear fuel represents a challenge for the safeguards community. Ideally, the characteristic gamma-ray emission lines from different isotopes provide an observable suitable for this task. However, these lines are generally lost in the fierce flux of radiation emitted by the fuel. The rates are so high that detector dead times limit measurements to only very small solid angles of the fuel. Only through the use of carefully designed view ports and long dwell times are such measurements possible. Recent advances in multilayer grazing-incidence gamma-ray optics provide one possible means of overcoming this difficulty. With a proper optical and coating design, such optics can serve as a notch filter, passing only narrow regions of the overall spectrum to a fully shielded detector that does not view the spent fuel directly. We report on the design of a mirror system and detector and a number of experimental measurements.

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Gamma-ray mirrors for direct measurement of spent nuclear fuel

Pivovaroff

Ziock

Fernández-Perea

et al. 2014

Nuclear Instruments and Methods in Physics Research Section A:

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Physics of Reflective Optics for the Soft Gamma-Ray Photon Energy Range

et al. 2013

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Traditional multilayer reflective optics that have been used in the past for imaging at x-ray photon energies as high as 200 keV are governed by classical wave phenomena. However, their behavior at higher energies is unknown, because of the increasing effect of incoherent scattering and the disagreement between experimental and theoretical optical properties of materials in the hard x-ray and gamma-ray regimes. Here, we demonstrate that multilayer reflective optics can operate efficiently and according to classical wave physics up to photon energies of at least 384 keV. We also use particle transport simulations to quantitatively determine that incoherent scattering takes place in the mirrors but it does not affect the performance at the Bragg angles of operation. Our results open up new possibilities of reflective optical designs in a spectral range where only diffractive optics (crystals and lenses) and crystal monochromators have been available until now.

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Optical constants in the hard x-ray/soft gamma-ray range

Cited by 2 publications

References 15 publications

Gamma-ray mirrors for direct measurement of spent nuclear fuel

Gamma-ray mirrors for direct measurement of spent nuclear fuel

Physics of Reflective Optics for the Soft Gamma-Ray Photon Energy Range

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