End Station Research Articles

Grazing incidence off-plane lamellar grating as a beam splitter for a 1-Å free electron laser

A beam splitter based on the diffraction grating working in the grazing incidence conical diffraction is proposed for x-ray free-electron laser (XFEL) experiments with coherent beams in plasma and atomic physics. Such a beam splitter can provide undistorted wavefronts, high-power radiation scattering, and split beams with equal intensities, which propagate with delay along different paths to the target chamber of the XFEL end station. Using the PCGrate software based on rigorous electromagnetic theory and developed for the short-wavelength range, it is shown that the plane grating with lamellar groove profile of a certain depth, operating in grazing conical incidence mount (grooves are parallel to the incident beam), separates three beams in the −1, 0, and +1 orders with close diffraction efficiency. Numerical simulation predicts 23–27% absolute efficiency for 0.1-nm incident radiation in each separated order of a bulk or multilayer grating, taking into account the atomic level roughnesses and interdiffusion. When using a multilayer coating based on Ru/C or Ru/B4C pairs, the optimum grazing angle providing approximately equal efficiencies is ∼1.038° which is four times higher than for the Pt-coated grating. Such optimization of radiation geometry, groove profile shape, and multilayer coating parameters can be performed for various XFEL wavelengths. The proposed grating, in addition to diffraction, technological, and design advantages over the beam splitter based on a set of perfect crystals, can be fabricated and tested using currently available methods.

The use of the Climate-science Computational End Station (CCES) development and grand challenge team for the next IPCC assessment: an operational plan

The grand challenge of climate change science is to predict future climates based on scenarios of anthropogenic emissions and other changes resulting from options in energy and development policies. Addressing this challenge requires a Climate Science Computational End Station consisting of a sustained climate model research, development, and application program combined with world-class DOE leadership computing resources to enable advanced computational simulation of the Earth system. This project provides the primary computer allocations for the DOE SciDAC and Climate Change Prediction Program. It builds on the successful interagency collaboration of the National Science and the U.S. Department of Energy in developing and applying the Community Climate System Model (CCSM) for climate change science. It also includes collaboration with the National Aeronautics and Space Administration in carbon data assimilation and university partners with expertise in high-end computational climate research.

Probing complex materials with coherent soft X-rays

We motivate the use of coherent soft X-ray beams to study materials that exhibit complex nanoscale behaviors. A new beamline and magnetic scattering end station that has been constructed and commissioned at the ALS will be described. Finally, we present some initial results that indicate the performance of the beamline.

A pragmatic algorithm for the train-set routing: The case of Korea high-speed railway

This paper presents a two-phased train-set routing algorithm to cover a weekly train timetable with minimal working days of a minimal number of train-sets. First, relax maintenance requirements and obtain minimum cost routes by solving the polynomial relaxation. Then, maintenance-feasible routes are generated from the crossovers of the minimum cost routes. This pragmatic approach seems particularly effective for the high-speed railway systems, where the railway topology is relatively simple with few end stations while the trains are frequent. Applied to the current weekly timetable of the Korea high-speed railway, we could find an optimal feasible routing, which is an 8.8% improvement over the current routing generated by a set partitioning approach based on a path generation scheme.

Fast Client-Based Connection Recovery for Soft WLAN-to-Cellular Vertical Handoff

Wireless local area network (WLAN)-to-cellular vertical handoff (VHO) involves time-consuming procedures that may significantly disrupt real-time communication. When a soft handoff is anchored by an enterprise private branch exchange (PBX)/gateway, handoff execution can take several seconds due to the time required to establish the cellular-to-PBX call leg. This situation is compounded by the fact that WLAN coverage may sometimes be lost far sooner than a VHO can be triggered and executed. In this paper, we propose and investigate the use of a VHO support node (VHSN) which is attached locally to the wired LAN hotspot infrastructure. When WLAN coverage is lost, the VHSN improves soft-handoff performance by quickly intercepting and redirecting the media flow through the local cellular base station using its cellular end-station attachment. This action can quickly recover the connection before the new cellular call leg is established. Unlike proxy forwarding, wireless multihop, and other infrastructure-modification schemes, the VHSN does not extend wireless coverage or perform infrastructure-based packet forwarding. Instead, the VHSN functions as both an (Ethernet) LAN and a cellular end station. Results will be presented which show the performance improvements that are possible using the proposed mechanism.

Exposure parameters in proton beam writing for hydrogen silsesquioxane

In proton beam writing (PBW) a focused MeV proton beam is scanned in a predetermined pattern over a resist (e.g. PMMA, SU-8 or HSQ), which is subsequently chemically developed. In e-beam writing as well as p-beam writing the energy loss of the primary beam is dominated by energy transfer to substrate electrons. Unlike the high energy secondary electrons generated during e-beam writing the secondary electrons induced by the primary proton beam have low energy and therefore a limited range, resulting in minimal proximity effects. The low proximity effects exhibited by p-beam writing coupled with the straight trajectory and high penetration of the proton beam enables the production of high aspect ratio, high density 3D micro and nanostructures with well defined smooth side walls to be directly written into resist materials. This property together with the stability and focusing power of the end station ensures even exposures with nm smoothness and allows fabrication of details down to the 20nm level. In this paper, we present results like contrast and sensitivity for PBW using, hydrogen silsesquioxane (HSQ) and XR-1541, both are non-C based resists. Unlike PMMA and SU-8 resist HSQ shows aging effects, requiring optimized processing parameters in PBW.

Infiltration and hydraulic behaviour of an anguiform furrow in heavy texture soils of Iran

Surface irrigation is used in smooth and land-levelled areas. Since land levelling is costly and it is not technically feasible in sloping lands, farmers in these areas in the Islamic Republic of Iran use anguiform (snake-shaped) furrow in traditional fashion instead of a straight furrow, particularly in heavy texture soils. Hydraulic and geometric parameters are different for anguiform furrow irrigation compared with the straight furrow irrigation. Research was conducted to determine the parameters of the Lewis–Kostikov infiltration equation and flow hydraulic and geometric parameters for an anguiform furrow in comparison with those for a straight furrow irrigation. The furrow geometric parameters were found to be variable in various furrow types and irrigation events. Differences were more pronounced between irrigation events than between furrow types. The Manning roughness coefficient in the anguiform furrow with real flow path was lower than that in the straight furrow in both the first and the next irrigations. The recession time in the anguiform furrow is higher due to greater water storage in upstream end stations. The basic infiltration rate in the anguiform furrow is higher (22 and 48% in the first and the next irrigations, respectively) than that in the straight furrow. The infiltration coefficients k were higher (two orders of magnitude) and the exponents a are smaller (about half) in the anguiform furrow than the straight furrow. Further more, it was indicated that the flow hydraulics in the anguiform furrow can be estimated by Fok–Bishop equation using the water surface hydraulic gradient, corresponding furrow geometry parameters and infiltration equation with the real water flow path.

Analysis of noise lines in the Virgo C7 data

The paper presents a description of the work of detection and identification of frequency lines in the Virgo dark fringe data from run C7. A number of methods are highlighted by which noise frequency lines are detected by data analysis and measurements in the laboratory. In this paper we give a description of the list of noise line candidates provided by the pulsar search analysis, the investigation of 10 Hz (and harmonics) noise, violin modes, noise from the end station buildings' air conditioners, sidebands in calibration lines and aliasing in the 4 kHz reconstructed data.

Soft X-ray spectromicroscopy beamline at the CLS: Commissioning results

The soft X-ray spectromicroscopy beamline (SM) at the Canadian Light Source (CLS) is a dedicated spectromicroscopy facility, consisting of an elliptically polarized undulator (EPU), a beamline based on a collimated PGM optimized for 100–2000 eV range and two end stations: scanning transmission X-ray microscope (STXM) and roll-in X-ray photoemission electron microscope (X-PEEM, from Elmitec GmbH). The overall system has achieved its design parameters with an on-sample flux of ∼10 8 ph/s@ R=3000, 0.5 A in STXM and ∼10 12 ph/s@ R=3000, 0.5 A in the PEEM, in each case at a spatial resolution exceeding 40 nm. It can also provide an energy resolving power above 10,000. A careful EPU calibration procedure enables advanced polarization measurements.

A new soft X-ray photoemission microscopy beamline at the National Synchrotron Light Source

We report the present status of a newly installed low-energy electron microscopy and photoelectron microscopy end station at beamline U5UA at the National Synchrotron Light Source. In first test experiments on sub-monolayer Au coverages deposited on Ru(0001) we demonstrate core-level and valence band photoelectron imaging with a lateral resolution of about 65nm at a field of view of 10μm. In contrast to other installations for photoelectron microscopy, the new NSLS end station uses illumination under normal incidence. The implications of this geometry for different applications are discussed.

A scanning focussed vertical ion nanobeam: A new UK facility for cell irradiation and analysis

A new initiative to build a vertical scanning focussed nanobeam is outlined. This is a collaboration between the Gray Cancer Institute and the University of Surrey. The new beam line will operate in both single ion and full current modes and will enable the irradiation of single cells in vitro with precisely counted numbers of ions, it will also enable the analysis of cells in vitro. The beam will be focussed and scanned and should be capable of irradiating 100,000 cells per hour. A new end station will enable the cells to be irradiated in an environmentally controlled environment and will enable the cells to be imaged both on-line and off-line. The beam line will be housed in its own purpose built building, with the area around the end station comprising a biological clean room.

Optimized end station and operating protocols for reflection extended x-ray absorption fine structure (ReflEXAFS) investigations of surface structure at the European Synchrotron Radiation Facility beamline BM29

The development of the capability to engineer the surface properties of materials to match specific requirements demands high quality surface characterization techniques. The ideal tool should provide chemically specific structural characterization as well as surface sensitivity and depth profiling. Ideally the characterization method should also be applicable to systems both with and without long range order. X-ray absorption spectroscopy fine structure, when using the standard transmission detection system, provides all this information with the significant exception of surface sensitivity. In contrast, by detecting the reflected instead of the transmitted beam, it encompasses all these requirements because when the incident beam impinges onto a sample surface at glancing angles, in conditions close to the total reflection, only the outermost regions of the system under study are sampled. Such a technique provides information about the local structure as a function of depth as well as thin layer structure in the case of layered samples. Although it is potentially the ideal tool to study surface modified materials, experimental difficulties have hampered its widespread use in the fields of surface and materials sciences. As a solution to the experimental challenges, we provide a detailed description of an appropriate experimental station, the sample requirements, the measuring protocols, and software routines needed to optimize the collection of the data. To illustrate the capabilities of the technique the results obtained for a model multilayer sample are presented and analyzed under the total external reflection approximation.

Scanning transmission x-ray microscopy with a configurable detector

A configurable charge-coupled-device (CCD) detector is used in a scanning transmission x-ray microscope to record the transmitted intensity distribution for every pixel in a raster scan of the sample. Real-time processing of the CCD frames gives simultaneous absorption and phase contrast image signals from a single scan. The CCD combines fast frame-transfer readout with very high sensitivity and makes use of x-ray to visible-light coupling to allow operation over a wide range of photon energies, from the oxygen K edge upwards. Tests on the Twinmic end station at the Elettra synchrotron are reported.

Construction and evaluation of an experimental station and reaction apparatus for the chemical reactions of aqueous solution systems with soft x rays from a sychrotron radiation light source

An efficient experimental system for the chemical reactions of various aqueous solutions using soft x rays from synchrotron radiation has been designed, constructed, and evaluated. This system was installed at an end station on a beamline (BL-11) at the Synchrotron Radiation Center of Ritsumeikan University. To protect the storage ring and the beamline from accidental vacuum breaks and contamination caused by unexpected solution leakage in the reaction apparatus, the system has two main protection sections: a differential vacuum pumping section equipped with orifice gaskets of very small aperture and an emergency interlocking system section equipped with a fast closing shutter, etc., in addition to a safety mechanism in the reaction apparatus section. The outline of the system and preliminary experimental data obtained in the evaluation of the system are described.

Terrestrial biogeochemistry in the community climate system model (CCSM)

Described here is the formulation of the CASA′ biogeochemistry model of Fung, et al., which has recently been coupled to the Community Land Model Version 3 (CLM3) and the Community Climate System Model Version 3 (CCSM3). This model is presently being used for Coupled Climate/Carbon Cycle Model Intercomparison Project (C4MIP) Phase 1 experiments. In addition, CASA′ is one of three models – in addition to CN (Thornton, et al.) and IBIS (Thompson, et al.) – that are being run within CCSM to investigate their suitability for use in climate change predictions in a future version of CCSM. All of these biogeochemistry experiments are being performed on the Computational Climate Science End Station (Dr. Warren Washington, Principle Investigator) at the National Center for Computational Sciences at Oak Ridge National Laboratory.

High-pressure monochromatic powder diffraction using a Bragg-Laue monochromator and a walker cell

Abstract The multi-anvil high-pressure facility on beamline 16.4 of the Synchrotron Radiation Source at Daresbury Laboratory has been upgraded from energy-dispersive diffraction operation to easily interchangeable energy-dispersive and angle-dispersive operation by the addition of a Laue–Bragg monochromator and an imaging plate detector. Details of the Laue–Bragg monochromator and endstation configuration are given. The performance of the end station is illustrated with data collected as part of a high temperature-pressure study of lawsonite.

Infrared and terahertz spectromicroscopy beam line BL6B(IR) at UVSOR-II

We have recently installed an infrared (IR)–terahertz (THz) beam line BL6B at UVSOR-II. The beam line collects a large acceptance angle of 215(H) × 80(V) mrad 2 to obtain high flux in the IR and THz regions. A “magic mirror” with vertical angle focusing was employed as the first mirror. The mirror chamber was directly connected to the bending magnet chamber for collecting the high flux and high brilliance IR and THz light. The obtained performance and the outline of the end stations are reported.

In situ X-ray absorption spectroscopy—A probe of cathode materials for Li-ion cells

In situ X-ray absorption spectroscopy is a powerful emerging technique that has the capability to observe the changes in ongoing electrochemical reactions. It is already well established in materials science, and it is becoming a significant tool for the electrochemical community. As with all X-ray absorption spectroscopies, extended X-ray absorption fine structure (EXAFS) has the advantage of being element specific. Interpretation of the spectra at different states of charge can provide very useful quantitative and qualitative information about the valence change of the constituent elements in the cathode material during the ongoing electrochemical reaction, the degree of distortion or changes in structure from the initial state of charge to the final state of charge and provide valuable information about the extent of degradation of the cathode material during continuous cycling. It can also provide valuable insight about how the nature of the electrochemical reactions changes when one of the transition metal constituents is removed or increased in content in the cathode material. It is often important to adjust the composition of the cathode material in order to achieve high specific capacity and long-term stability in Li-ion cells. This article details the development of the in situ XAS techniques to study electrochemical reactions using various X-ray absorption spectroscopies which are now possible with the advent of third generation synchrotron radiation sources and improved end stations. The strength of in situ EXAFS techniques is illustrated using examples of various interesting transition metal oxides. In this way, we aim to encourage chemists, chemical engineers and materials scientists to consider in situ X-ray absorption spectroscopy as an effective tool for developing an understanding the electronic structure of materials and the changes that it undergoes during electrochemical reactions.

Managing a High Speed LAN using Distributed Artificial Intelligence

This study is concerned with a practical application of distributed artificial intelligence for managing the high data rate bus structured local area computer network that uses deterministic multiple access protocol. In the selected network that is managed using distributed artificial intelligence, the dynamic sharing of the available bandwidth among stations is achieved by forming train to which each station may append a packet after issuing a reservation. Reservation and packet transmissions are governed by the reception of control packets (token) issued by the network end stations. Managing approach that was suggested depends on using intelligent autonomous agents, which are responsible for various tasks among it: election of the end stations, the recovery from failures, and the insertion of new stations in the network. All these tasks are based on the use of special tokens.

Synchronization systems for ERLs

The next generation light sources require synchronization of (soft and hard) X-rays to beamline and end station lasers. The relative timing jitter required will be of the order of the photon pulse length down to a few fs between sources separated by ∼100–500 m. Also the synchronization of electron beam production at the photo-injector, the beam acceleration and compression in the linac, the electron arrival time at the insertion devices and some of the beam diagnostics in the linac must be synchronized with a precision of the same order of magnitude. The concept of synchronization is described and limiting factors for synchronization in Energy Recovery Linacs are discussed.