Photoelectron emission microscopy and its application to the study of polymer surfaces

The X-ray Photoelectron Emission Microscopy (X-PEEM) at the Advanced Light Source (ALS) has a spatial resolution of 0.2 microns at an accelerating voltage of 12kV. The tunability of the photon energy is used to provide chemical state information using near edge X-ray absorption fine structure (NEXAFS) spectroscopy on the sub-micrometer scale. The homogeneity of thin films of polymer blends was studied for various film thicknesses. The polystyrene/polyvinylmethylether film of 194 {angstrom} showed protrusions of 2-3{mu}m diameter with an enriched polystyrene content while the polystyrene/polystyreneacrylonitrile 504 {angstrom} thick films showed 5-6 {mu}m segregated regions without any topological structure

Influence of Growth Method on K3Sb Photocathode Structure and Performance

Future high brightness photoelectron sources delivering gt;100 mA average current call for a new generation of photocathodes. Materials which qualify for this purpose should exhibit low intrinsic emittance, long lifetime and high quantum efficiency at photon energies in the visible range of the spectrum to relax drive laser requirements. A combination of material science techniques are used to determine the influence of the growth parameters on structure and performance of photocathode materials . In situ XRR, XRD and GiSAXS measurements were performed at the synchrotron radiation sources, NSLS and CHESS. The growth of K3Sb, a precursor material of one of the prime candidates CsK2Sb, was studied intensively to optimize this intermediate growth step in terms of quantum efficiency and roughness. Three methods, a layer by layer type and a super lattice type were examined. K3Sb exists in two crystallographic phases, namely cubic and hexagonal. The cubic phase exhibits a higher quantum efficiency at 532 nm than the hexagonal phase and transforms more easily into CsK2Sb, tuning this phase is believed to be one of the key parameters in the CsK2Sb growt

An ultrafast x-ray detector system at an elliptically polarizingundulator beamline

An ultrafast x-ray detector system is under development atLawrence Berkeley National Laboratory (LBNL) for application primarily tostudyies of ultrafast magnetization dynamics. The system consists of a fslaser, an x-ray streak camera and an ellipitically polarization undulator(EPU) beamline. Polarized x-rays from an EPU can be used to measure x-raymagnetic circular dichroism (XMCD) of a sample. XMCD has the uniqueability to independently measure orbit and spin magnetization withsub-monolayer sensitivity and element specificity. The streak camera hassimultaneously a sub-picosecond temporal resolution and a high spatialresolution. The combination of the streak camera and EPU allows us tostudy the transfer of angular momentum from spin to orbit to the latticein the sample on an ultrafast time scale. We describe here theperformance of the ultrafast detector, the laser and the x-raysynchronization system. The observation of the demagnetization process ofdifferent samples demonstrates the ability of the apparatus

Element-specific spin and orbital momentum dynamics of Fe/Gdmultilayers

The role of orbital magnetism in the laser-induced demagnetization of Fe/Gd multilayers was investigated using time-resolved X-ray magnetic circular dichroism at 2-ps time resolution given by an x-ray streak camera. An ultrafast transfer of angular momentum from the spin via the orbital momentum to the lattice was observed which was characterized by rapidly thermalizing spin and orbital momenta. Strong interlayer exchange coupling between Fe and Gd led to a simultaneous demagnetization of both layers

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Soft X-ray Optics for Spectromicroscopy at the Advanced Light Source

A variety of systems for performing spectromicroscopy, spatially resolved spectroscopy, are in operation or under construction at the Advanced Light Source (ALS). For example, part of the program is centered around the surface analysis problems of local semiconductor industries, and this has required the construction of a microscope with wafer handling, fiducialization, optical microscopy, coordinated ion beam etching, and X-ray Photoelectron Spectroscopy (XPS) integrated in this case with Kirkpatrick-Baez (K-B) grazing incidence micro-focusing optics. The microscope is to be used in conjunction with a highly efficient entrance slitless Spherical Grating Monochromator (SGM). The design and expected performance of this instrument will be described, with emphasis on the production of the elliptically curved surfaces of the K-B mirrors by elastic bending of flat mirror substrates. For higher resolution, zone-plate (Z-P) focusing optics are used and one instrument, a Scanning Transmission X-ray Microscope (STXM) is in routine operation on undulator beamline 7.0. A second Z-P based system is being commissioned on the same beamline, and differs from the STXM in that it will operate at Ultra-High Vacuum (UHV) and will be able to perform XPS at 0.1 {micro}m spatial resolution. Spatially resolved X-ray Absorption Spectroscopy (XAS) can be performed by imaging electrons photoemitted from a material with a Photo-Emission Electron Microscope (PEEM). The optical requirements of a beamline designed for PEEM are very different to those of micro-focus systems and they give examples of bending magnet and undulator based instruments