The generation of two X-ray pulses with tunable nanosecond scale time separations has recently been demonstrated
at the Linac Coherent Light Source using an accelerator based technique. This approach offers the opportunity
to extend X-ray Photon Correlation Spectroscopy techniques to the yet unexplored regime of nanosecond
timescales by means of X-ray Speckle Visibility Spectroscopy. As the two pulses originate from two independent
Spontaneous Amplified Stimulated Emission processes, the beam properties fluctuate from pulse pair to pulse
pair, but as well between the individual pulses within a pair. However, two-pulse XSVS experiments require the
intensity of the individual pulses to be either identical in the ideal case, or with a accurately known intensity
ratio. We present the design and performances of a non-destructive intensity diagnostic based on measurement
of scattering from a transparent target using a high-speed photo-detector. Individual pulses within a pulse pair
with time delays as short as 0.7 ns can be resolved. Moreover, using small angle coherent scattering, we characterize
the averaged spatial overlap of the focused pulse pairs. The multi-shot average-speckle contrasts from
individual pulses and pulse pairs are compared.
A hard X-ray delay line device capable of splitting single FEL X-ray pulses into two adjustable fractions and
recombining them with the goal of performing X-ray Photon Correlation Spectroscopy and pump - probe type
studies was designed. The performance of the device has been verified at the XPP and XCS instruments of
LCLS. The measured throughput of the device at 7.9 keV is 3.6%. The coherence properties of the LCLS beam
passing through the delay line were investigated by analyzing speckle patterns produced by single LCLS pulses.
A high speckle contrast of 0.69 was found, indicating the feasibility of performing coherence based experiments
with the delay line.
Recently, with increasing lightness and miniaturization of high resolution camera phones, the demand for aspheric glass
lens has increased because plastic and spherical lenses are unable to satisfy the required performance. An aspheric glass
lens is fabricated by high temperature and pressure molding using a tungsten carbide molding core, so precision grinding
and coating technology for the molding core surface is required.
In this paper, the optimal grinding condition of the tungsten carbide molding core was found after applying DOE to the
development of the aspheric glass lens for the 3 mega pixel and 2.5 magnifications optical zoom for camera phone
module. Also, the ultra precision grinding process was investigated under this condition by experiment. Rhenium-Iridium(Re-Ir) coating was applied on the ground surface of the tungsten carbide molding core. The influence of Re-Ir
coating on the form accuracy and surface roughness was compared and evaluated. The form accuracy and surface
roughness of the molding core were improved by application of Re-Ir coating on the surface of the tungsten carbide
molding core. Aspheric lenses were also molded with the non-coated molding core and the Re-Ir coated molding core.
Form accuracy(PV) and surface roughness(Ra) were measured. The form accuracy of the aspheric glass lens improved
about 0.01 μm (aspheric surface) and the surface roughness by about 0.5 nm (aspheric surface).
This paper summarizes recent in situ x-ray analyses of the growth of GaAs by organometallic vapor phase epitaxy (OMVPE). This growth was carried out using tertiarybutylarsine (TBAs) and trimethylgallium (TMG) as the source materials. Examples of in situ x-ray measurements are given including x-ray absorption studies of gas phase behavior and x-ray scattering studies of layer-by-layer growth.
Using a new in situ analysis tool, grazing incidence x-ray scattering, we have studied the surface reconstructions present prior
to and during growth of ZnSe by organometallic vapor phase deposition. We have established that the GaAs native oxide is
chemically reduced by the hydrogen ambient present during pre-growth heating. Following this cleaning procedure, the
growth of ZnSe was found to occur in the presence of a p(2x1) reconstruction, characteristic of an array of Se dimers. This
new technique can easily be extended to other growth systems.