Closed source experimental system for soft x-ray spectroscopy of radioactive materials

Abstract

An instrumental and experimental setup for soft x-ray spectroscopy meeting the requirements of a closed source for radioactivity is described. The system consists of a vacuum sealed cell containing the sample, mounted on a tubing system to ensure compatibility with most standard manipulators. The soft x rays penetrate a thin x-ray window separating the interior of the cell from the vacuum in the experimental chamber. Our first results for single crystal PuO(2) confirm the feasibility of experiments using the setup. The results are consistent with results of first principles calculations and previously recorded spectra obtained using a standard open source setup. The results show that the closed source experimental system can be used to collect valuable experimental data from radioactive materials.

Insights into the sonochemical synthesis and properties of salt-free intrinsic plutonium colloids

“…The spectra were evaluated by curve fitting analysis using constrained Gaussian line shapes and an arctan step function. Gaussian functions were constrained to reproduce the pre-edge, edge and post-edge of crystalline PuO 2 as reported in the literature303132.…”

“…Moreover, the spectrum of hydrolytic colloid does not exhibit multiple scattering features at 555 eV and 568 eV that are typical for crystalline PuO 2 . The main edge shape itself is split in two peaks, one at 538 eV and the other at 543 eV, that can be attributed to the strong influence of hydrated and/or hydrolysed forms of Pu(IV) on the total oxygen state3132. In addition, the contribution from nitrate ions to the experimental O K-edge NEXAFS spectra of hydrolytic Pu colloid also cannot be completely excluded33.…”

Density Functional Theory Studies of the Electronic Structure of Solid State Actinide Oxides

“…More recently, high-resolution photoemission (PES) spectra 54 reproduced in Figure 3 (top) were recorded at photon energies between 16 and 87 eV along the Γ−X azimuth of the Brillouin zone, indicating the width of this 5f peak to be ∼130 meV, corresponding to a small but observable dispersion in the 5f band. The low-energy unoccupied bands were recently 56,57 Notice that the O Kα emission spectrum, which probes the occupied states, does not exhibit a two peak structure as is the case in UO 2 . This is potentially tied to changes in the band structure, as well as the different selection rules in effect compared with PES (the O Kα emission essentially reflects the O 2p partial DOS).…”

Optical band gap of NpO2 and PuO2 from optical absorbance of epitaxial films

“…10 As the author notes, PuO 2 has a tendency to lose oxygen to form sub-stoichiometric oxides. 9 For the PuO 2.0 sample that was measured, the value of 1.8 eV was obtained from a fit of data from 200 to 1000 C. Below 200 C, the data fall far below the extrapolated line. The data from room temperature to 200 C are nearly linear with a slope that yields a barrier to electronic conduction of approximately 3 eV.…”

“…The reports of PuO 2 single crystals are limited to two examples of crystal PuO 2 formation from a flux comprising a mixture of Li 2 O and MoO 3 and the color of the crystals is reported as black in contrast to the olive green color of bulk PuO 2 powders. [7][8][9] Most references to a band gap for PuO 2 cite the McNeilly paper from 1962 which reports an activation barrier to electronic conduction of 1.8 eV. 10 For neptunium oxide, there are many more reports of single crystals, [11][12][13] once again the only measurement of the band gap is from a measurement of the activation barrier to electronic conduction.…”