Detailed spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source synchrotron facility in Berkeley, CA. The high-brightness synchrotron source is coupled at this beamline to a Thermo-Electron Continuμm XL infrared microscope. Two types of resolution tests in both the mid-IR (using a KBr beamsplitter and an MCT-A* detector) and in the near-IR (using a CaF 2 beamsplitter and an InGaAS detector) were performed and compared to a simple diffractionlimited spot size model. At the shorter wavelengths in the near-IR the experimental results begin to deviate from only diffraction-limited. The entire data set is fit using a combined diffraction-limit and demagnified electron-beam source size model. This description experimentally verifies how the physical electron beam size of the synchrotron source demagnified to the sample stage on the endstation begins to dominate the focussed spot size and therefore spatial resolution at higher energies. We discuss how different facilities, beamlines, and microscopes will affect the acheivable spatial resolution.
SynopsisSpatial resolution measurements at ALS Beamline 1.4.4 are used to determine the wavelengths at which a cross-over from diffraction-limited to electron beam source size-limited resolution occurs. Performance is then predicted for different synchrotrons, beamline optics, and endstation microscopes. AbstractSpatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source in Berkeley, CA, a third generation synchrotron light source. This beamline couples the highbrightness synchrotron source to a Thermo-Electron Continuμm XL infrared microscope. Two types of resolution tests were performed in both the mid-IR and near-IR. The results are compared to a diffraction-limited spot size theory. At shorter near-IR wavelengths the experimental results begin to deviate diffraction-limited so a combined diffraction-limit and electron-beam source size model is employed. This description shows how the physical electron beam size of the synchrotron source begins to dominate the focused spot size at higher energies.The transition from diffraction-limited to electron beam size-limited performance is a function of storage ring parameters and the optical demagnification within the beamline and microscope optics. The discussion includes how different facilities, beamlines, and microscopes will affect the acheivable spatial resolution. As synchrotron light sources and other next generation accelerators such as energy recovery LINAC's and free-electron lasers achieve smaller beam emittances, beta-functions, and/or energy spreads, diffraction-limited performance can continue to higher energy beams, perhaps ultimately into the extreme ultraviolet.
Absolute photoionization cross sections for Kr 5+ were measured in the photon energy range 74-175 eV using synchrotron radiation. For comparison, a detailed energy scan of the electron-impact ionization cross section was made in the same energy range and normalized to previously published absolute measurements. The Flexible Atomic Code and Cowan atomic structure code were used to calculate energy levels, excitation energies, and oscillator strengths for 3d → np, 3d→ nf, and 4s → np autoionizing transitions from the ground and metastable states. Within the experimental uncertainty, oscillator strengths determined from the photoionization measurements are in agreement with both calculations. Excitation-autoionization and resonant excitation-double-autoionization features are evident in the electron-impact ionization cross section.
feedback are at the cutting edge of technology, and the conceptual design of autonomous systems represents a research frontier in mechatronics. We expect that the current operator-assisting UMR will evolve into a system endowed with progressively increasing autonomy capable of significantly increasing reliability of protein micro-crystal harvesting and reproducibility of cryo-cooling. In addition, advanced micro-manipulation robotics will open the field to new science and emerging crystallization technologies of far reaching impact. Major improvements in operational precision have given the UMR the capability of manipulating crystals significantly smaller than 10 microns thus facilitating nano-crystallization, harvesting from micro-fluidics, nano-diffraction techniques and novel seeding strategies.
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