The Design of a Reflection Electron Energy Loss Spectrometer Attachment for Low Voltage Scanning Electron Microscopy

This paper presents the design of a reflection electron energy spectrometer (REELS) attachment for low voltage scanning electron microscopy (LVSEM) applications. The design is made by carrying out a scattered electron trajectory ray paths simulation. The spectrometer attachment is small enough to fit on the specimen stage of an SEM, and aims to acquire nanoscale spatially resolved REELS information. It uses a retarding field electrostatic toroidal sector energy analyzer design, which is able to lower the kinetic energies of elastically backscattered electrons to pass energies of 10 eV or less. For the capture of 1 keV BSEs emitted in the polar angular range between 40 to 50°, direct ray-tracing simulations predict that the spectrometer attachment will have an energy resolution of around 0.4 eV at a pass energy of 10 eV, and 0.2 eV at a pass energy of 5 eV. This predicted performance will make it a suitable REELS attachment for SEMs that use field emission electron sources.

Modification of a Cylindrical Mirror Analyzer for High Efficiency Photoelectron Spectroscopy on Ion Beams

An existing cylindrical mirror analyzer (CMA) that was initially equipped with eight channeltrons detectors has been modified to install large micro-channel plate detectors to perform parallel detection of electrons on an energy range corresponding to ~12% of the mean pass energy. This analyzer is dedicated to photoelectron spectroscopy of ions ionized by synchrotron radiation. The overall detection efficiency is increased by a factor of ~20 compared to the original analyzer. A proof of principle of the efficiency of the analyzer has been done for Xe5+ and Si+ ions and will allow photoelectron spectroscopy on many other ionic species.

Double-transmembrane domain reduces fusion rate by increasing lipid-protein mismatch

ABSTRACTMembrane fusion mediated by Soluble N-ethylmaleimide-sensitive factor activating protein receptor (SNARE) proteins is an important cellular process. For neuronal SNAREs, the single transmembrane domain has been proposed to pass zippering energy to membranes for inducing fast fusion. In contrast, the SNARE protein, syntaxin 17, for membrane fusion involved in autophagosome maturation contains an unusual V-shape double-transmembrane domain that may influence its capability to pass energy. Here, we showed that this double-transmembrane domain significantly reduces fusion with an in vitro reconstitution system. Through theoretic modelling, we found that this V-shape double-transmembrane domain increases lipid-protein mismatch, which reduces the energy transduction for fusion. Moreover, our model also revealed the involvement of 2-3 SNAREs in a general fusion process.SIGNIFICANT STATEMENTSoluble N-ethylmaleimide-sensitive factor activating protein receptors (SNAREs) serve as the molecular machine to mediate membrane fusion. The zipper formation of core structure extending to membranes by two single transmembrena domains (TMDs) is the main driving force of membrane fusion. The role of TMD in fusion is unclear. By adding an extra TMD, we found that the hydrophobic mismatch effect between the thickness of the membrane and the length of TMDs plays an important role in regulating fusion.

Experience with online modeling tools during the CBETA fractional arc test and single pass commissioning

The Cornell-Brookhaven CBETA machine is a four-pass Energy Recovery Linac (ERL) with a Non-scaling Fixed-Field Alternating gradient (NS-FFA) arc. For online modeling of single particle dynamics in CBETA, a customized version of the Tao program, which is based upon the Bmad toolkit, has been developed. This online program, called CBETA-V, is interfaced to CBETA’s EPICS control system. This work describes the online modeling system and initial experience during machine running, as well as subsequent developments since its first implementation.

Highly Reproducible Secondary Electron Imaging under Electron Irradiation Using High-Pass Energy Filtering in Low-Voltage Scanning Electron Microscopy

The reproducibility of contrast in secondary electron (SE) imaging during continuous electron irradiation, which caused surface contamination, was investigated using SE high-pass energy filtering in low-voltage scanning electron microscopy (SEM). According to high-pass energy-filtered imaging, dopant contrast in an indium phosphide remained remarkably stable during continuous electron irradiation although the contrast in unfiltered SE images decreased rapidly as a contamination layer was formed. Charge neutralization and the SE energy distributions indicate that the contamination layer induces a positive charge. This results in a decrease of low-energy SE emissions and reduced dopant contrast in unfiltered SE images. The retention of contrast was also observed in high-pass energy-filtered images of a gold surface. These results suggest that this imaging method can be widely used when SE intensities decrease under continuous electron irradiation in unfiltered SE images. Thus, high-pass energy-filtered SE imaging will be of a great assistance for SEM users in the reproducibility of contrast such as a quantitative dopant mapping in semiconductors.