Beam Size Research Articles

TriSol: A major upgrade of the TwinSol RNB facility

We report here on the recent upgrade of the TwinSol radioactive nuclear beam (RNB) facility at the University of Notre Dame. The new TriSol system includes a magnetic dipole to provide a second beamline and a third solenoid which acts to reduce the size of the radioactive beam on target.

Solution scattering and scanning based imaging at the life sciences X-ray scattering beamline (LiX).

Small-angle X-ray scattering allows one to obtain information on nanoscale particle size and structure. The method is popular in the biological and soft matter scientific communities and has been widely used at synchrotron radiation sources worldwide. This article presents current status of multipurpose small-angle scattering beamline for life sciences (LiX) at NSLS-II. The beamline has dedicated experimental setup and controls for high throughput solution scattering and raster scanning based imaging technique. In-house automation combined with six-axis robot allows efficient solution sample transfer, loading, rinsing and cleaning, the whole process spans around 1 minute per sample. Mail-in access allows user to collect the data and access it remotely concurrently through the JupyterHub. A loading dock can store 360 samples from multiple users, with QR codes that allows data collection and storage under proper user directory with correct access permissions. Users can send samples either in 96 well plate or in LIX sample holder format. In case of 96-well plates a liquid handling robot is used to transfer samples to LIX holders, additionally samples could be diluted or mixed right before the measurement. For scanning based imaging beam size can be focused down to few microns using two stage focusing scheme. Fly scanning allows for expediting data collection and mitigate any radiation damage. An In vacuum setup allows to reduce background scattering and improve signal to noise, especially vital for low scattering samples. Data processing functions are made available to users to further process data and construct structural maps.

Excitation of Multiperiodic Kink Motions in Solar Flare Loops: Possible Application to Quasiperiodic Pulsations

Magnetohydrodynamic (MHD) waves are often invoked to interpret quasiperiodic pulsations (QPPs) in solar flares. We study the response of a straight flare loop to a kink-like velocity perturbation using three-dimensional MHD simulations and forward model the microwave emissions using the fast gyrosynchrotron code. Kink motions with two periodicities are simultaneously generated, with the long-period component (P L = 57 s) being attributed to the radial fundamental kink mode and the short-period component (P S = 5.8 s) to the first leaky kink mode. Forward modeling results show that the two-periodic oscillations are detectable in the microwave intensities for some lines of sight. Increasing the beam size to (1″)2 does not wipe out the microwave oscillations. We propose that the first leaky kink mode is a promising candidate mechanism to account for short-period QPPs. Radio telescopes with high spatial resolutions can help distinguish between this new mechanism and such customary interpretations as sausage modes.

Investigation of the multiple characteristics of the self-mixing effect subject to a single particle.

As a compact interferometry technique, self-mixing interferometry (SMI) is a promising tool for micro particle detection in biochemical analysis and the monitoring of laser manufacturing processing, and currently SMI based micro particle detection is attracting increasing attention. However, unlike the typical displacement or vibration measurement driven by a macro target, only a small amount of literature has targeted the SMI effect induced by a single micro moving particle. In this paper, two numerical models were investigated to describe the characteristics of the signal sparked by individual particle. We compared the measurement results with the two models' simulations in three signal characteristic aspects: the temporal waveform, frequency spectrum, and phase profile. From these results, we established that both amplitude modulation and frequency modulation effects apply under different conditions in the self-mixing process. And for the first time, we analyzed the effect of the laser illumination spot size on the particle-induced SMI signal features with two optical arrangements. When the laser beam size is larger than the particle size, the signal bursts are likely to result from frequency modulation, and vice versa. Our results can improve the capability of SMI technology in particle size discrimination and particle sorting.

Design of the proton and electron transfer lines for AWAKE Run 2c

The Advanced Wakefield (AWAKE) Run 1 experiment, which concluded in 2018, achieved electron acceleration to 2GeV via plasma wakefield acceleration driven by 400GeV, self-modulated proton bunches extracted from the CERN SPS. The Run 2c phase of the experiment aims to advance these results by demonstrating acceleration up to about 10GeV while preserving the quality of the accelerated electron beam. For Run 2c, the Run 1 proton transfer line will be reconfigured to shift the first plasma cell 40m longitudinally and a second plasma cell will be added 1m downstream of the first. In addition, a new 150MeV beamline will be required to inject a witness electron beam, with a beam size of several microns, into the second plasma cell to probe the accelerating fields. Proposed adjustments to the proton transfer line and the design of the 150MeV electron transfer line are detailed in this paper.

Influence of laser beam aberrations compensation and spot size on the transmittance in native and optically cleared skeletal muscles

Light propagation and penetration inside tissues highly affect the optical imaging of biological tissues. Two major factors influence that; the first is associated with the dense scattering properties of tissues. Consequently, optical clearing (OC) methods have been developed to reduce tissue scattering by matching the tissue layers’ refractive indices via different protocols. The second factor is related to the illuminating wavefront and the size of the incident light beam. The present work monitored the optical transmittance of skeletal muscles after applying different OC approaches (physical OC using 99%-glycerol immersion and photothermal OC using IR-laser irradiation). First, the optical transmittance of the samples before and after the two OC procedures were compared, revealing a transmittance increase of 300% and 20%. Then, the laser beam wavefront aberrations were compensated in real-time by utilizing an active-adaptive Shack-Hartmann wavefront sensor system to provide an ideal illumination wavefront. Finally, the transmittance of the samples was compared using uncompensated and compensated laser wavefronts providing a 35% increase in the transmittance after aberrations compensation. Moreover, the aberration-free incident laser beam’s transmittance with different spot diameters was investigated. The results revealed that the larger beam diameter provided higher transmittance, hence higher optical penetration within the tissue.

Zastosowanie technologii laserowej w usuwaniu zbędnego owłosienia

Laser hair removal requires knowledge of their physical basis and the biophysical phenomena they induce in the skin. Lasers differ in such categories as wavelenght, Energy density and laser beam size. These elements are important while selecting the right device for the skin type and individual characteristics of the patient. Knowledge of the physiology of hair and the photothermolysis that occurs during epilation, allows the treatment to be carried out correctly and safely, and the entire proces of hair elimination to be controlled. Previous studies indicate a numer of factors that determine the effectiveness of the procedure, including the parameters of the device or skin type. Despite the high degree of safety and effectiveness of the laser epilation procedure, it is also pointed out that there are undesirable consequences that may appear in response to the effects of laser light.

Parametric study of melt pool geometry in hybrid plasma arc-laser melting process for additive manufacturing application

Wire-based hybrid arc-laser additive manufacturing is suitable for producing large metallic parts (metres in scale) with high deposition rates and near-net-shape. In this process, the surface quality and dimensional accuracy of the deposited parts are determined by the melt pool geometry. However, how to control the melt pool in the hybrid process is complex due to the multiple parameters that can be used. In this study, control of melt pool geometry by investigating different process parameters, including laser power, travel direction, arc-laser separation distance, laser beam size, and arc current in the hybrid plasma transferred arc (PTA)-laser process, was studied systematically. It was found that a larger melt pool was achieved with the PTA-leading configuration compared to that with the laser-leading configuration due to a higher laser absorption occurred with the former configuration. The melt pool was enlarged by either increasing the laser power or arc current due to the increased energy input. However, if the laser power density is high enough to determine the melt pool depth, the increasing arc current has very little effect on melt pool depth but only increases the melt pool width. In addition, the melt pool became shallower and wider when using a larger laser beam. The arc-laser separation distance had a minor effect on the melt pool geometry due to the fixed energy input used in the studied cases. The results of this study provide a reference for melt pool control in wire-based hybrid arc-laser additive manufacturing.

Validation of an EGSnrc-based Monte Carlo model for a complex 2D-array for technical QA measurements of a linear accelerator.

Multi-axis ionization chamber arrays can be used for quality assurance (QA) and measurement of linear accelerator (linac) specific data. In this work, the ability of the IC Profiler (Sun Nuclear Corp., Melbourne, Florida) detector array to measure the photon beam quality specifier %dd(10) and TPR20, 10 was investigated. To investigate the method for beam energy QA using a two-dimensional detector array, a Monte Carlo-based model of the detector array was developed and validated. A Monte Carlo-based model of the IC Profiler detector array with Quad Wedge accessories was developed in detail from drawings provided by the manufacturer using the egs++ class library from the EGSnrc code system. Monte Carlo simulations were used to calculate the absorbed dose in the 251 ionization chambers of the IC profiler in the 6 MV Elekta Precise radiation field. To validate the results from the Monte Caro simulations, measurements were performed on clinical 6 MV linacs. To vary the photon beam quality of the Elekta 6 MV linac, the current of the bending magnet was varied. Furthermore, the area ratio was calculated from IC Profiler measurements with the Quad Wedgeaccessories. Measurements as well as Monte Carlo simulations confirmed the linear relationship between the area ratio and the investigated photon beam quality specifier %dd(10) and TPR20, 10 for the investigated radiation source. Furthermore, the Monte Carlo-simulated data were within the 95% confidence interval of the linear fit to the measured data. This enabled the Monte Carlo-based IC Profiler model to be used for further investigations. The values were calculated for various electron beam sizes and the angle of incidence on the target of thelinac. A Monte-Carlo-based model of the detector array was developed, which could successfully reproduce measurements, demonstrating that even very complex geometries can be modeled in EGSnrc. Moreover, the study showed that the validated Monte Carlo model has the potential to investigate variations in beam parameters and their effects on AR ratios and %dd(10) that may not be investigated experimentally. While these findings may help users gain a deeper understanding of the QA method, the Monte Carlo model enables other complex investigations, such as the simulation of measurements in the presence of magnetic fields, or the simulation of measurements on novel treatment delivery techniques anddevices.

Generating Ultralong-Superoscillation Nondiffracting Beams with Full Control of the Intensity Profile

Nondiffracting light beams receive substantial attention in various areas due to their properties of diffractionless propagation and achievable subwavelength beam size. Extending the propagation distance and compressing the beam size of nondiffracting beams are crucial to their practical applications. However, it remains challenging to achieve nondiffracting light beams with a subwavelength subdiffracting transverse size and a long propagation distance with controllable intensity profiles in both transverse and longitudinal directions. Here, we propose an optimization method to generate an ultralong-superoscillation nondiffracting light beam with full control of the beam intensity profile. A 45\ensuremath{\lambda}-long-superoscillation nondiffracting light beam, the transverse sizes of which are within the range of 0.37\ensuremath{\lambda}--0.4\ensuremath{\lambda} along the propagation axis, is experimentally demonstrated by a metalens based on continuous phase modulation using geometrical phase metasurfaces. Our method provides an attractive way to controllably generate ultralong-superoscillation nondiffracting beams on a subwavelength scale and might find fascinating applications in optical manipulation, materials processing, data storage, microscopy, and spectroscopy.

Dynamics of Hermite–Gaussian laser beam in plasma and terahertz generation

In the present work, the dynamical study of a Hermite–Gaussian (HG) laser beam propagating through plasma with relativistic nonlinearity has been carried out. Furthermore, the dependency of THz generation on the HG laser dynamics has also been investigated. Self-focusing of laser beam inside plasma is achieved due to the modification in electron’s rest mass due to their motion at relativistic velocities. The coupled differential equations obtained using the method of moment determines the variation in spot size of laser beam and have been solved numerically. The laser beam propagating through plasma excites the plasma wave and the nonlinear coupling of HG beam and plasma wave generates THz radiation. It has been observed that THz generation strongly depends upon the variation of spot size, TEM modes, plasma density and intensity of laser beam. Furthermore, the self-trapping of HG laser beam has also been studied.

Mathematical considerations for evaluating X‐ray beam size in micro‐XRF analysis

AbstractMicro X‐ray fluorescence spectrometry (micro‐XRF) is conducted for elemental imaging and analysis of small regions, by focusing on primary X‐rays. An appropriate beam diameter evaluation is essential as is directly related to the spatial resolution of micro‐XRF imaging. The X‐ray beam size was experimentally determined from the XRF intensity with respect to the scanning distance (thin‐wire scanning method) or its differentiated curve (knife‐edge scanning method). However, a beam diameter is not currently evaluated in a mathematically appropriate method and is known to differ significantly from the actual value under certain conditions. A formula to correct this difference has been proposed; however, to the best of our knowledge, no study has discussed the performance of the correction formula and conditions under which they can be applied. By mathematically analyzing the overlapping volume between the X‐ray beam and the scanning material, we succeeded in deriving an appropriate fitting function that replaces the Gaussian function taking into account the effect of absorption. The fitting function is effective for each method. This technique was applied to evaluate the micro X‐ray beam created using polycapillary X‐ray focusing optics. Both thin‐wire and knife‐edge scanning methods were used with wires of different sizes to determine the X‐ray beam size. The beam size obtained by the conventional fitting function can be accurately corrected using the newly derived correction formula. Simulations were performed using the derived fitting function, and the applicability of the correction formulas was demonstrated.

Ionoacoustic application of an optical hydrophone to detect proton beam range in water.

Proton range uncertainty has been the main factor limiting the ability of proton therapy to concentrate doses to tumors to their full potential. Ionoacoustic (IA) range verification is an approach to reducing this uncertainty by detecting thermoacoustic waves emitted from an irradiated volume immediately following a pulsed proton beam delivery; however, the signal weakness has been an obstacle to its clinical application. To increase the signal-to-noise ratio (SNR) with the conventional piezoelectric hydrophone (PH), the detector-sensitive volume needs to be large, but it could narrow the range of available beam angles and disturb real-time images obtained during beam delivery. To prevent this issue, we investigated a millimeter-sized optical hydrophone (OH) that exploits the laser interferometric principle. For two types of IA waves [γ-wave emitted from the Bragg peak (BP) and a spherical IA wave with resonant frequency (SPIRE) emitted from the gold fiducial marker (GM)], comparisons were made with PH in terms of waveforms, SNR, range detection accuracy, and signal intensity robustness against the small detector misalignment, particularly for SPIRE. A 100-MeV proton beam with a 27 ns pulse width and 4 mm beam size was produced using a fixed-field alternating gradient accelerator and was irradiated to the water phantom. The GM was set on the beam's central axis. Acrylic plates of various thicknesses, up to 12mm, were set in front of the phantoms to shift the proton range. OH was set distal and lateral to the beam, and the range was estimated using the time-of-flight method for γ-wave and by comparing with the calibration data (SPIRE intensity versus the distance between the GM and BP) derived from an IA wave transport simulation for SPIRE. The BP dose per pulse was 0.5-0.6Gy. To measure the variation in SPIRE amplitude against the hydrophone misalignment, the hydrophone was shifted by±2mm at a maximum in lateral directions. Despite its small size, OH could detect γ-wave with a higher SNR than the conventional PH (diameter, 29mm), and a single measurement was sufficient to detect the beam range with a submillimeter accuracy in water. In the SPIRE measurement, OH was far more robust against the detector misalignment than the focused PH (FPH) used in our previous study [5%/mm (OH) versus 80%/mm (FPH)], and the correlation between the measured SPIRE intensity and the distance between the GM and BP agreed well with the simulation results. However, the OH sensitivity was lower than the FPH sensitivity, and about 5.6-Gy dose was required to decrease the intensity variation among measurements to less than 10%. The miniature OH was found to detect weak IA signals produced by proton beams with a BP dose used in hypofractionated regimens. The OH sensitivity improvement at the MHz regime is worth exploring as the next step.

Characterization of relativistic electron–positron beams produced with laser-accelerated GeV electrons

The characterization of an electron–positron beam generated from the interaction of a multi-GeV electron beam with a lead plate is performed using GEANT4 simulations. The dependence of the positron beam size on driver electron beam energy and lead converter thickness is investigated in detail. A pancake-like positron beam structure is generated with a monoenergetic multi-GeV driver electron beam, with the results indicating that a 5 GeV driver electron beam with 1 nC charge can generate a positron beam with a density of 1015–1016 cm−3 at one radiation length of lead. In addition, we find that electron–positron beams generated using above-GeV electron beams have neutralities greater than 0.3 at one radiation length of lead, whereas neutralities of 0.2 are observed when using a 200 MeV electron beam. The possibility of observing plasma instabilities in experiments is also examined by comparing the plasma skin depth with the electron–positron beam size. A quasi-neutral electron–positron plasma can be produced in the interaction between a 1 nC, 5 GeV electron beam and lead with a thickness of five radiation lengths. Our findings will aid in analyzing and interpreting laser-produced electron–positron plasma for laboratory astrophysics research.

Generation and propagation of Airy beams and 1-inch diameter focusing optics using three-dimensional-printed polymer optics

The additive manufacture of polymer optical elements has the promise of reducing component weight, providing new design capabilities, and enhanced performance for a wide variety of military and commercial optical systems. We review progress in the development of three-dimensional (3D)-printed gradient index (GRIN) lenses and optical phase masks. The 3D printing process uses a modified commercial inkjet printer and ultraviolet curable polymers that have specific nanoparticles added to them to modulate the index of refraction. Complex optical phase masks for the generation of Airy laser beams and polymer GRIN lenses to replace conventional glass lenses used in a telescope or riflescope are created. The generation and propagation of Airy beams using these polymer-generated optical phase masks have been investigated and analyzed through experimentation, simulations, and comparison with recent theoretical predictions. Airy beams have been generated using the conventional approach with a spatial light modulator and compared to the 3D printed optical phase masks. The maximum nondiffracting propagation distance of an aperture truncated Airy beam was experimentally measured. The results show that the maximum nondiffracting propagation distance of a laboratory generated Airy beam is proportional to x02, the Airy beam waist size squared. The size of the Gaussian envelope beam has a weaker effect on the Airy beam propagation distance. The experimental results were compared with current theoretical models. A set of 1-inch-diameter 100-mm focal length polymer GRIN lenses have been made using 3D printing. Transmission and modulation transfer function results for the lenses are reported.

Detachable interface toward a low-loss reflow-compatible fiber coupling for co-packaged optics (CPO).

High-density reflow-compatible fiber I/O is one of the challenges for co-packaged optics (CPO). This paper developed a detachable coupling interface based on expanded beam edge coupling, which can be applied for optical coupling between lasers, PICs, and fibers, seamlessly supporting many channels with high efficiency. It comprises a removable fiber connector and a permanent chip/device connector, in which microlens/lens arrays are used for waveguide mode expansion and MT-like connectors are used for position registration. An effective alignment scheme based on beam detection was developed and implemented in an assembly station for building the removable fiber connectors, while the permanent chip/device connector was assembled by active alignment to a pre-made fiber connector mated with a registration connector. Promising results were obtained from the proof-of-concept demonstrations of the coupling from SiP PIC and III/V lasers to fibers using the off-the-shelf lenses and modified MT registration connectors. In both cases, less than 1 dB coupling loss was achieved with an expanded beam size of 160 µm in diameter. Even with a relatively large lens offset of ∼35 µm, the detachable fiber array connectors showed good interchangeability. Such a coupling interface is expected to be solder-reflow compatible by replacing the plastic registration connectors with ceramic ones, making it a promising candidate for the solution to CPO fiber I/O.

A New Method for Determining the Size of a Synchrotron Radiation Beam in the Focus of a Compound Refractive Lens

A new method is proposed for determining experimentally the size of a synchrotron radiation beam in the focus of planar compound refractive lenses. The method consists in measuring the angular divergence of radiation after the focus using Bragg diffraction in a perfect crystal during its rotation. This method determines the beam size, which depends only on the focusing properties of the lenses in use, in contrast to other currently applied methods. The efficiency of the proposed approach has been experimentally demonstrated using nanofocusing planar silicon lenses as an example.

Ultrahigh Performance of Concrete using Manufactured Sand

The resistance and durability of concrete structures can be improved by using ultra-high performance concrete (UHPC). A crucial component of energy conservation and concrete cost reduction is the use of locally available materials. In this study, the effects of a common type of locally accessible manufactured sand (MS) on the characteristics of UHPC were investigated from both a physical and chemical standpoint. The main objective of the current study is to use locally available materials to create a UHPC with a compressive strength of 100MPa. The impact of fine materials, binder type and content, mixer type, steel fibres, and curing regimes on the concrete’s compressive strength was examined in this study. The use of high strength concrete has various benefits, including a reduction in the size of beams and columns and an increase in the height of buildings with multiple stories. In recent years, high strength concrete has seen increased use in civil engineering. By minimising non-homogeneity, porosity, and micro-cracks in the concrete and its zone of transition, high strength is made achievable. Super plasticizers and additional cementing substances such granulated blast furnace slag, silica fume, and natural pozzolana can be used to achieve it. Concrete with a high modulus of elasticity is strong. On cement, fine aggregate, and coarse aggregate, preliminary studies have been conducted. In the current study, 920KK is employed as a chemical admixture and silica fume is used as a mineral admixture. For M100 concrete, the w/c ratio is taken to be 0.25. The mix proportion for M100 grade concrete can be calculated by following the design process suggested by the ACI Method as 1:0.454:1.527.

A concept of "materials" diffraction and imaging beamline for SKIF: Siberian circular photon source.

Over the next decade, the extremely brilliant fourth generation synchrotron radiation sources are set to become a key driving force in materials characterization and technology development. In this study, we present a conceptual design of a versatile "Materia" diffraction and imaging beamline for a low-emittance synchrotron radiation facility. The beamline was optimized for operation with three main principal delivery regimes: parallel collimated beam ∼1mm beam size, micro-focus regime with ∼10μm beam spot size on the sample, and nano-focus regime with <100nm focus. All regimes will operate in the photon energy range of 10-30keV with the key feature of the beamline being fast switching between them, as well as between the various realizations of diffraction and imaging operation modes while maintaining the target beam position at the sample, and with both spectrally narrow and spectrally broad beams up to the energy band ΔE/E of 5 × 10-2. The manuscript presents the details of the principal characteristics selected for the insertion device and beamline optics, the materials characterization techniques, including the simulations of thermal load impact on the critical beamline optics components. Significant efforts were made to design the monochromators to mitigate the very high beam power load produced by a superconducting undulator source. The manuscript will be of interest to research groups involved in the design of new synchrotron beamlines.

Diffraction-limited mid-infrared microspectroscopy to reveal a micron-thick interfacial water layer signature.

Mid-infrared microspectroscopy is a non-invasive tool for identifying the molecular structure and chemical composition at the scale of the probe, i.e. at the scale of the beam. Consequently, investigating small objects or domains (commensurable to the wavelength) requires high-resolution measurements, even down to the diffraction limit. Herein, different protocols and machines allowing high-resolution measurements in transmission mode (aperture size (i.e., beam size) from 15 × 15 μm to 3 × 3 μm) are tested using the same sample. The model sample is a closed cavity containing a water-air assemblage buried in a quartz fragment (fluid inclusion). The spectral range covers the water stretching band (3000-3800 cm-1), whose variations are followed as a function of the distance to the cavity wall. The experiments compare the performance of one focal plane array (FPA) detector associated with a Globar source with respect to a single-element mercury cadmium telluride (MCT) detector associated with a supercontinuum laser (SCL) or a synchrotron radiation source (SRS). This work also outlines the importance of post-experimental data processing, including interference fringe removal and Mie scattering correction, to ensure that the observed spectral signatures are not related to optical aberrations. We show that the SCL and the SRS-based setups detect specific spectral features along the quartz boundary (solid surface), invisible to the FPA imaging microscope. Additionally, the broadband SCL thus has the potential to substitute at the laboratory scale the SRS for conducting diffraction-limited high-resolution measurements.