Exit Slits Research Articles

The soft X-ray spectromicroscopy beamline BL08U1A upgrade at SSRF.

Beamline BL08U1A is a soft X-ray spectromicroscopy beamline at Shanghai Synchrotron Radiation Facility (SSRF) that exhibits the capabilities of high spatial resolution (30 nm) and high energy resolving power (over 104). As a first-generation beamline of SSRF, owing to its continuous operation over the last ten years, an urgent upgrade of the equipment including the monochromator was deemed necessary. The upgrade work included the overall construction of the monochromator and replacement of the mirrors upstream and downstream of the monochromator. Based on its original skeleton, two elliptically cylinder mirrors were designed to focus the beam horizontally, which can increase the flux density by about three times on the exit slits. Meanwhile, the application of variable-line-space gratings in the monochromator demonstrates the dual functions of dispersing and focusing on the exit slits which can decrease abberations dramatically. After the upgrade of the main components of the beamline, the energy range is 180-2000 eV, the energy resolving power reaches 16333 @ 244 eV and 12730 @ 401 eV, and the photon flux measured in the experimental station is over 2.45 × 109 photons s-1 (E/ΔE= 6440 @ 244 eV).

Design of a plane grating with multilayer coating for the soft X-ray tomography beamline

An alternate multilayer plane grating has been designed for the soft X-ray tomography beamline. At this beamline, a grating with 600 line/mm and Au coating has already been set up to serve the energy range from 260 eV to 1200 eV. To fit the original optical design, a varied-line-spacing plane grating optimized at 2473 eV will be used in this beamline. The groove depth is 2.5 nm and its duty cycle is 0.5. The B4C/Mo alternate layers with period 30 are selected to enhance diffraction efficiency in the energy range 1100 eV -- 2600 eV. The varied-line-spacing plane grating paired with a matched multilayer plane mirror constitutes a monochromator to provide energetic photons. Based on the designed multilayer conditions, the calculated diffraction efficiency of alternate multilayer varied-line-spacing plane grating is about 0.24 at 2473 eV; the calculated photon flux is about 2.3 × 1011 photons/s. The resolving power is about 1670; the openings of the entrance and exit slits are 25 and 50 μm respectively.

Magnetograph Saturation and the Open Flux Problem

Abstract Extrapolations of line-of-sight photospheric field measurements predict radial interplanetary magnetic field (IMF) strengths that are factors of ∼2–4 too low. To address this open flux problem, we reanalyze the magnetograph measurements from different observatories, with particular focus on those made in the saturation-prone Fe i 525.0 nm line by the Mount Wilson Observatory (MWO) and the Wilcox Solar Observatory (WSO). The total dipole strengths, which determine the total open flux, generally show large variations among observatories, even when their total photospheric fluxes are in agreement. However, the MWO and WSO dipole strengths, as well as their total fluxes, agree remarkably well with each other, suggesting that the two data sets require the same scaling factor. As shown earlier by Ulrich et al., the saturation correction δ −1 derived by comparing MWO measurements in the 525.0 nm line with those in the nonsaturating Fe i 523.3 nm line depends sensitively on where along the irregularly shaped 523.3 nm line wings the exit slits are placed. If the slits are positioned so that the 523.3 and 525.0 nm signals originate from the same height, δ −1 ∼ 4.5 at the disk center, falling to ∼2 near the limb. When this correction is applied to either the MWO or WSO maps, the derived open fluxes are consistent with the observed IMF magnitude. Other investigators obtained scaling factors only one-half as large because they sampled the 523.3 nm line farther out in the wings, where the shift between the right- and left-circularly polarized components is substantially smaller.

Theoretical analysis of Hanbury Brown and Twiss interferometry at soft-x-ray free-electron lasers

In this work we provide theoretical background for the analysis of second-order correlation functions in experiments performed at the soft x-ray free-electron lasers (XFELs). Typically, soft x-ray beamlines at XFELs are equipped by the variable line spacing (VLS) monochromators. We perform examination of the beam propagation through such VLS monochromator taking specially into account the interplay between the finite monochromator resolution and the exit slits width. We then provide general analysis of the second-order correlation intensities in spectral and spatial domains. Finally, we connect these functions with the statistical properties of the beam incoming to the monochromator unit in the limit of Gaussian Schell-model pulses.

Operation of photon diagnostic imagers for beam commissioning at the European XFEL.

X-ray photon beam diagnostic imagers are located at 24 positions in the European XFEL beam transport system to characterize the X-ray beam properties, and to give feedback for tuning and optimization of the electron acceleration and orbit, the undulators, and the X-ray optics. One year of commissioning allowed experience to be gained with these imagers, which will be reported here. The sensitive Spontaneous Radiation imager is useful for various investigations in spontaneous radiation mode: for undulator adjustments and for low-signal imaging applications. Thehigh-resolution Free-Electron Laser imager, 10 µm spatial resolution, is extensively used for the monitoring of beam position, spot size and shape, gain curve measurements, and also for beam-intensity monitoring. The wide field-of-view pop-in monitors (up to 200 mm) are regularly used for alignment and tuning of the various X-ray optical components like mirrors, slits and monochromators, and also for on-line beam control of a stable beam position at the instruments. The Exit Slit imager after the soft X-ray monochromator provides spectral information of the beam together with multi-channel plate based single-pulse gating. For particular use cases, these special features of the imagers are described. Some radiation-induced degradation of scintillators took place in this initial commissioning phase, providing useful information for better understanding of damage thresholds. Visible-light radiation in the beam pipe generated by upstream bending magnets caused spurious reflections in the optical system of some of the imagers which can be suppressed by aluminium-coated scintillating screens.

High-speed VUV spectroscopy for edge impurity line emission measurements in HL-2A tokamak

A 20 cm focal length normal incidence vacuum ultraviolet (VUV_20 cm) monochromator with a fast time response has been developed for measuring edge impurity line emission in the wavelength range of 300–2000 Å on an HL-2A tokamak. An aberration corrected concave holographic grating with 1200 grooves/mm is adopted in the monochromator, which provides a wavelength dispersion of 40 Å mm−1. The aperture is f/4.5. A channel electron multiplier is used as a detector. The time resolution of the system is 17 μs. Wavelength calibration of the system has been done by using a hollow cathode light source in the laboratory with helium and argon gases. The obtained signals of helium and argon spectra are very strong since the inner surface of the monochromator vacuum chamber is blackened and the stray light level is then significantly reduced. The optical property of the system has been examined by scanning the width of the entrance and exit slits. The system is then installed at the mid-port of the HL-2A tokamak and typical line emissions from the HL-2A plasma are measured. Time behaviors of edge impurity line emissions are observed with the fast time response system in different plasma confinement regimes, especially in the H-mode discharges. The result shows that the VUV_20 cm system works very well to measure the edge impurity line emissions in the edge localized modes phase of H-mode discharges.

On the design of miniature parallel-plate differential mobility classifiers

The effect of design parameters of particle classification channel on the performance of miniature parallel-plate differential mobility classifier (i.e., mini-plate DMCs) was numerically investigated in this work to establish the general design guideline for compact parallel-plate DMCs. The design parameters under consideration were the aspect ratio and the cross-sectional area of the particle classification channel, the percentage of aerosol inlet and exit slit opening (relative to the full width of the classification channel), and the aerosol injection angle. COMSOL Multiphysics 5.3® and MATLAB R2016a® were used in this numerical modeling. Prior to the parametric study, our modeling was validated by comparing the numerical result with the experimental data published by Liu and Chen (2016a). Our study shows that the performance of mini-plate DMCs deteriorated as the channel aspect ratio reduced to a value less than eight. The opening percentage of aerosol inlet and exit slits was also an important factor for the mini-plate DMC design. The peak of DMC transfer function decreased as the aerosol opening percentages reduced to a value less than 35% in cases having the same opening percentage for aerosol inlet and exit slits. In cases having the aerosol inlet slit opening percentage fixed while varying the exit slit percentage, the DMC transfer function started to deteriorate with the decrease of aerosol exit slit percentage. The worst scenario on the DMC transfer function was observed when the exit slit was reduced to a round exit. Using the 2-D model as the reference, a mini-plate DMC with reasonable performance should have the channel aspect ratio at least greater than 10 and the slit opening percentages of 75–90% for both aerosol inlet and exit.

The Far Ultra-Violet imager on the ICON mission.

ICON Far UltraViolet (FUV) imager contributes to the ICON science objectives by providing remote sensing measurements of the daytime and nighttime atmosphere/ionosphere. During sunlit atmospheric conditions, ICON FUV images the limb altitude profile in the shortwave (SW) band at 135.6 nm and the longwave (LW) band at 157 nm perpendicular to the satellite motion to retrieve the atmospheric O/N2 ratio. In conditions of atmospheric darkness, ICON FUV measures the 135.6 nm recombination emission of O+ ions used to compute the nighttime ionospheric altitude distribution. ICON Far UltraViolet (FUV) imager is a CzernyTurner design Spectrographic Imager with two exit slits and corresponding back imager cameras that produce two independent images in separate wavelength bands on two detectors. All observations will be processed as limb altitude profiles. In addition, the ionospheric 135.6 nm data will be processed as longitude and latitude spatial maps to obtain images of ion distributions around regions of equatorial spread F. The ICON FUV optic axis is pointed 20 degrees below local horizontal and has a steering mirror that allows the field of view to be steered up to 30 degrees forward and aft, to keep the local magnetic meridian in the field of view. The detectors are micro channel plate (MCP) intensified FUV tubes with the phosphor fiber-optically coupled to Charge Coupled Devices (CCDs). The dual stack MCP-s amplify the photoelectron signals to dominate the CCD noise and the rapidly scanned frames are co-added to digitally create 12-second integrated images. Digital on-board signal processing is used to compensate for geometric distortion and satellite motion and to achieve data compression. The instrument was originally aligned in visible light by using a special grating and visible cameras. Final alignment, functional and environmental testing and calibration were performed in a large vacuum chamber with a UV source. The test and calibration program showed that ICON FUV meets its design requirements and is ready to be launched on the ICON spacecraft.

Analysis of effective pore pressure in asphalt pavement based on computational fluid dynamics calculation

A micromechanical model was established based on the fluid dynamics theory. This model could be used to calculate several kinds of data when the asphalt pavement under the influence of traffic loading is in water-saturated condition. The results showed that the maximum pressure inside the effective pore was located at the junction between exit slits and the pore wall. There was a positive correlation between the pressure and the vehicle speed. Therefore, the repeated traffic loading could cause emulsification, shift and even peeling of the asphalt membrane. Moreover, the bigger size of the exit slit is, the higher velocity of the fluid has. The high velocity flow keeps scouring both the exit slit and the lower boundary of pore wall. It will cause a bigger slit. Pressure distribution inside the effective pore is related to the number of the exit slit which connect with the pore. More exit slits means bigger pressure inside the effective pore. In addition, if asphalt membranes at exit slits have micro-cracking, the cumulative damage could appear easily and asphalt membranes could be peeled easily. Finally, a test was conducted so as to obtain the bonding strength and adhesion strength between asphalt and aggregate. Then, we can get accurate damage form and position during the scour process by comparing the numerical simulation results with experiment results.

The SPECIES beamline at the MAX IV Laboratory: afacility for soft X-ray RIXS and APXPS.

SPECIES is an undulator-based soft X-ray beamline that replaced the old I511 beamline at the MAX II storage ring. SPECIES is aimed at high-resolution ambient-pressure X-ray photoelectron spectroscopy (APXPS), near-edge X-ray absorption fine-structure (NEXAFS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) experiments. The beamline has two branches that use a common elliptically polarizing undulator and monochromator. The beam is switched between the two branches by changing the focusing optics after the monochromator. Both branches have separate exit slits, refocusing optics and dedicated permanent endstations. This allows very fast switching between two types of experiments and offers a unique combination of the surface-sensitive XPS and bulk-sensitive RIXS techniques both in UHV and at elevated ambient-pressure conditions on a single beamline. Another unique property of the beamline is that it reaches energies down to approximately 27 eV, which is not obtainable on other current APXPS beamlines. This allows, for instance, valence band studies under ambient-pressure conditions. In this article the main properties and performance of the beamline are presented, together with selected showcase experiments performed on the new setup.

Optimizing Water Transport through Graphene-Based Membranes: Insights from Nonequilibrium Molecular Dynamics.

Recent experimental results suggest that stacked layers of graphene oxide exhibit strong selective permeability to water. To construe this observation, the transport mechanism of water permeating through a membrane consisting of layered graphene sheets is investigated via nonequilibrium and equilibrium molecular dynamics simulations. The effect of sheet geometry is studied by changing the offset between the entrance and exit slits of the membrane. The simulation results reveal that the permeability is not solely dominated by entrance effects; the path traversed by water molecules has a considerable impact on the permeability. We show that contrary to speculation in the literature, water molecules do not pass through the membrane as a hydrogen-bonded chain; instead, they form well-mixed fluid regions confined between the graphene sheets. The results of the present work are used to provide guidelines for the development of graphene and graphene oxide membranes for desalination and solvent separation.

Development of a High Resolution Analyzing Magnet System for Heavy Molecular Ions

At the King Abdulaziz City for Science and Technology (KACST, Saudi Arabia), a versatile ion-beam injector was constructed to provide the electrostatic storage ring with the required high-quality ion beams. In order to remove the ambiguity over the ion mass due to the exclusive application of electric fields in the set-up, the injector is being equipped with a high resolution mass analyzing magnet. A high resolution Analyzing Magnet System has been designed to provide a singly-charged ion beam of kinetic energy up to 50 keV, mass up to 1500 Amu, and with the mass resolution fixed to Δm/m =1:1500. The system includes specific entrance and exit slits, designed to sustain the required mass resolution. Furthermore, specific focusing and shaping optics have been added upstream and downstream the system, in order to monitor and adapt the shape of the ion beam at the entrance and exit of the system, respectively. The present paper gives an overview on the design of this mass analyzing magnet system together with the upstream/downstream adapting optics.

Performance of a Halo Ion Trap Mass Analyzer with Exit Slits for Axial Ejection

The halo ion trap (IT) was modified to allow for axial ion ejection through slits machined in the ceramic electrode plates rather than ejecting ions radially to a center hole in the plates. This was done to preserve a more uniform electric field for ion analysis. An in-depth evaluation of the higher-order electric field components in the trap was also performed to improve resolution. The linear, cubic and quintic (5th order) electric field components for each electrode ring inside the IT were calculated using SIMION (SIMION version 8, Scientific Instrument Services, Ringoes, NJ, USA) simulations. The preferred electric fields with higher-order components were implemented experimentally by first calculating the potential on each electrode ring of the halo IT and then soldering appropriate capacitors between rings without changing the original trapping plate design. The performance of the halo IT was evaluated for 1% to 7% cubic electric field (A (4)/A (2)) component. A best resolution of 280 (m/Δm) for the 51-Da fragment ion of benzene was observed with 5% cubic electric field component. Confirming results were obtained using toluene, dichloromethane, and heptane as test analytes.

Experimental observation of invariance of spectral degree of coherence with change in bandwidth of light

An experimental study is conducted to show the effect of the change in bandwidth of light on the spectral degree of coherence at a pair of points in the cross section of a beam. For this purpose a polychromatic source and a monochromator with variable entrance and exit slits were used to produce a variable bandwidth source. The classic Young's interferometer was used to produce an interference pattern. The spectral measurements of the visibility of the interference fringes show that the spectral degree of coherence remains unaffected by the change in the frequency passband of the light.

Temporal behaviour of toroidal rotation velocity in the TCABR tokamak

A new method for determining the temporal evolution of plasma rotation is reported in this work. The method is based upon the detection of two different portions of the spectral profile of a plasma impurity line, using a monochromator with two photomultipliers installed at the exit slits. The plasma rotation velocity is determined by the ratio of the two detected signals. The measured toroidal rotation velocities of C III (4647.4 Å) and C VI (5290.6 Å), at different radial positions in TCABR discharges, show good agreement, within experimental uncertainty, with previous results (Severo et al 2003 Nucl. Fusion 43 1047). In particular, they confirm that the plasma core rotates in the direction opposite to the plasma current, while near the plasma edge (r/a > 0.9) the rotation is in the same direction. This technique was also used to investigate the dependence of toroidal rotation on the poloidal position of gas puffing. The results show that there is no dependence for the plasma core, while for plasma edge (r/a > 0.9) some dependence is observed.

CLS ID-10 chicane configuration: From “Simple Sharing” to extended performance with high-speed polarization switching

The chicane scheme adopted for the elliptically polarized undulators (EPU) in the ID10 section at the Canadian Light Source (CLS) not only permits independent operation of two beamlines, but also allows to redirect beams from two EPUs into a single beamline with a performance similar to a “dedicated” configuration. Fast switching at kHz rates will be achieved by piezo shutters located after exit slits which will block the light of alternate polarization.

Performance evaluation of long differential mobility analyzer (LDMA) in measurements of nanoparticles

Performance of a long differential mobility analyzer (LDMA) in measurements of nanoparticles was evaluated experimentally and numerically. In the evaluation of the LDMA measurements, silver particles in a size range of 5–30 nm were used under an increased flow rate. The numerical calculation method was used for calculating the particle trajectory in the LDMA, and the results were used for a comparison with Stolzenburg's transfer function. Using the CFD method, the flow around the aerosol inlet slit was analyzed, and the resulting particle mobility distribution was compared with that for an ideal flow. The resulting flow effect on the penetration efficiency caused by the inlet and exit slits were negligible when a well-designed system was used. The experimental measurements of mobility distributions were in good agreement with the theoretical prediction of particle size ranges over 10 nm, but some discrepancies were observed when particle size ranges were below 10 nm in size. The numerical calculation estimated the discrepancy found below the 10 nm particle size ranges.

A NEW XUV BEAMLINE ON A MULTI-POLE WIGGLER IN THE SRS

An XUV beamline has been constructed on the SRS synchrotron radiation source at Daresbury Laboratory, exploiting the output from a 2 T multi-pole wiggler. The beamline is based on an SGM design and produces photons in the energy range 40–350 eV. By taking a 7.5 mrad fan, a high flux of between 1 × 1013 and 1 × 1014 photons/s/300 mA ring current can be delivered, with a resolving power of around 1000. A Kirkpatrick–Baez mirror pair focuses the light onto the entrance slit of the monochromator. Using 10 · m entrance and exit slits, a resolving power of up to 10,000 can be achieved, with a flux of 0.5–2 × 1011 photons/s/300 mA. The calculated and measured performance is presented, with emphasis on the challenges associated with utilizing the XUV output of a high field MPW source. In addition, the scientific research programme is outlined.

Design of an ultra-high resolution and high flux cylindrical grating monochromator undulator beamline

An ultra-high resolution and high flux 6 m cylindrical grating monochromator (6 m-CGM) undulator beamline, covering the photon energies from 5 to 100 eV, has been designed and constructed at SRRC. Two branches, housing separate entrance slits chosen to provide different incident angles, are used to optimize the overall performance. In each branch, two cylindrical gratings are used with the grating included angle set at 150° and 130°, respectively, to cover low (5–30 eV) and high (15–100 eV) photon energy. Movable entrance and exit slits are used to enhance the beamline performance. The energy resolving power with both slit openings set at 10 μm is expected to reach 90,000 and 40,000 in the low and high energy branches, respectively. A photon flux of 6×10 10 and 3×10 11 photons/s/200 mA can be obtained at the respective energy resolving power of 90,000 and 40,000.

A low energy monochromator beamline at ELETTRA: conceptual design and scientific aims

A beamline using a Low Energy Monochromator Optimized at Normal incidence (LEMON) has been designed to match the bending magnet radiation characteristics of ELETTRA, the third generation source in Trieste. The beamline will use 4×6 mrad 2 of the emitted radiation cone and will be equipped with two interchangeable monochromators: one Normal Incidence Monchromator (NIM) and one Toroidal Grating Monochromator (TGM), both sharing the same focusing optics, entrance and exit slits. The expected performance of the beamline will be a photon energy range from 5 to 200 eV, a resolving power ranging from 100 000 to 500 and a photon flux up to 1×10 11 ph/s/0.1BW on the sample.