Diffuse Photon Density Waves (DPDWs) characterise photon migration through diffusive media in the frequency-domain. Theoretically, we describe DPDWs propagation using the diffraction theory based on the diffusion approximation to the transport equation. Experimentally, we study the propagation of 100 MHz-modulated DPDWs through (optical)-breast-like phantoms. The great interest of probing these phantoms lies in the fact that they contain very small optical inhomogeneities, with a diameter of 5 mm only and with inhomogeneitj^ackground absorption and scattering contrasts of 1.1,1.5,2.0 and 4.0 respectively. We show that both most contrasted inhomogeneities (in absorption and scattering) can be distinguished, while the 1.5 contrasted one is visible only in scattering. This is consistent with the measured actual accuracy of our set-up which is 0.3% in amplitude and 0.15¡ in phase. Experimental results are compared to simulations, time-domain experimental results and X-ray measurements.
Photon Migration through diffusive media studied in the frequency-domain is characterized by Diffuse Photon Density Waves (DPDWs). Theoretically, DPDWs propagation is described using the diffraction theory based on the diffusion approximation to the transport equation. Experimentally, 100 MHz modulated DPDWs are generated with our home-made frequency-domain set-up. The actual accuracy of this set-up is 0.3% in amplitude and 0.15 degree(s) in phase. The diffuse media probed are (optical)-breast-like phantoms which contain 5 mm-diameter inhomogeneities with inhomogeneity/background absorption and scattering contrasts of 1.1, 1.5, 2.0 and 4.0 respectively. Experimental results are compared to simulations and time-domain experimental results. Differences between absorption and scattering effects in the frequency-domain are highlighted. Main problems induced by phantom boundaries are presented. Two methods which aim to minimize lateral boundary effects are proposed and tested: the extrapolated lateral-boundary method and the direct polynomial or exponential fitting procedure. With these corrections, we are able to resolve well the two most contrasted inhomogeneities.
We propose the use of mass-limited, line emitting cryogenic targets for SXPL, which permit a continuous supply of targets without the problem of particulate debris and excessive heating of multilayer optics by an intense x-ray flux in wavelength regions outside the multilayer bandwidth. In preliminary experiments we measured the oxygen line emission in the vicinity of 13 nm. The x-ray emitting plasma was produced by using a laser intensity of 2 X 10<SUP>12</SUP> W/cm<SUP>2</SUP> on the surface of an ice target. From the observed crater on target we can deduce that clusters are also ejected from cryogenic targets.