Search

X-ray point source generated by X-pinches on the compact pulsed power device PPG-2 of Tsinghua University is well suited for phase-contrast imaging of weakly X-ray absorbing organism. Using six sets of photoconducting devices each covered by a filter of specific transmittance curve, the X-ray radiation energy spectra from Mo-wire and W-wire X-pinches were experimentally studied. It was found that X-ray with photon energy less than 2 keV takes the main part, about 70% of the total radiation, and the energy spectrum obeys exponential distribution; the bumps in the intervals of 2–3 keV for Mo and 4–6 keV for W may be attributed to the existence of line spectra such as L-shell of Mo and M-shell of W. Compared with the results of other groups, our measured X-ray energy yield were several times higher. The reasons may be attributed to differences in load current rising rate or different responses of X-ray detectors. [ABSTRACT FROM PUBLISHER]

The dynamic polarizabilities of Al atom at 19 wavelengths from 420 nm to 680 nm are measured experimentally for the first time. A 15 µm diameter Al wire is heated to the gas/ microdrop stage using a 3 kA, 25 ns pulsed current, and the energy deposition when the resistive voltage reaches its peak is 4.7 eV·atom -1 , which is higher than the atomization enthalpy of Al but much lower than its first ionization potential. Two laser interferometric images of the Al gas are obtained simultaneously using a 532 nm laser and an optical parametric oscillator laser. Then an integrated phase method is used to reconstruct the Al atomic linear density distribution based on the known atomic polarizability at 532 nm, which acts as a bridge between the two interferograms to obtain the relative atomic polarizability value at a specific wavelength with respect to the value at 532 nm. The measured dynamic polarizability of Al atom decreases from 13.5×10 -24 cm 3 to 9.4×10 -24 cm 3 as the wavelength increases from 420 nm to 680 nm with a measurement error of approximately ±10%. The experimental result fits well with an uncoupled Hartree-Fock approximation, and the reconstructed static polarizability of 8.13 ± 0.79×10 -24 cm 3 is well matched with reference measurement results.