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A new architecture for a flat panel three‐dimensional holographic display is proposed. We developed a beam steering backlight, which is achieved by the integration of a beam deflector and a coherent backlight unit. In addition, a hologram processor is implemented as a single‐chip FPGA. We built a flat prototype that is slim as 10cm thick. It shows high‐resolution holographic images with an improved viewing angle. [ABSTRACT FROM AUTHOR]

Recent developments on the electron optics simulator (EOS) are reported in this paper. The EOS is a finite element two-dimensional (2D) and three-dimensional (3D) electrostatic particle steady-state trajectory code that has been widely used for beam optics modeling of vacuum electronic devices. To extend the application scope and improve the computation efficiency, four significant advances have been made and are presented in this paper. First, the code is reprogrammed to consider physical models that contain dielectrics and to support charge excitation. Second, more primary particle emission models are added in EOS to meet the needs for simulating electron and ion optics devices for diverse applications. For the precise simulation of the secondary electron emission, the Vaughan model is improved, and the Furman model is newly added in EOS. Finally, the algebraic multigrid algorithm has been embedded in EOS, which can significantly improve the computation efficiency for problems with large-scale matrices. For these developments, the necessary principles and corresponding performance are shown in detail in this paper. [ABSTRACT FROM AUTHOR]

The paper considers the possibility of using the diamond‐silicon carbide composite Skeleton® with a technological coating of polycrystalline silicon as a substrate for X‐ray mirrors used with powerful synchrotron radiation sources (third+ and fourth generation). Samples were studied after polishing to provide the following surface parameters: root‐mean‐square flatness ≃ 50 nm, micro‐roughness on the frame 2 µm × 2 µm σ ≃ 0.15 nm. The heat capacity, thermal conductivity and coefficient of linear thermal expansion were investigated. For comparison, a monocrystalline silicon sample was studied under the same conditions using the same methods. The value of the coefficient of linear thermal expansion turned out to be higher than that of monocrystalline silicon and amounted to 4.3 × 10−6 K−1, and the values of thermal conductivity (5.0 W cm−1 K−1) and heat capacity (1.2 J K−1 g−1) also exceeded the values for Si. Thermally induced deformations of both Skeleton® and monocrystalline silicon samples under irradiation with a CO2 laser beam have also been experimentally studied. Taking into account the obtained thermophysical constants, the calculation of thermally induced deformation under irradiation with hard (20 keV) X‐rays showed almost three times less deformation of the Skeleton® sample than of the monocrystalline silicon sample. [ABSTRACT FROM AUTHOR]

A novel design methodology based on a current-tunable magnetic focusing system that can flexibly switch between Brillouin and immersive flow focusing modes is presented in this paper. Such a magnetic system, which comprises cascaded solenoid coils and pole pieces, could be used in beam optics systems of vacuum tubes, particle accelerators, and free-electron lasers. Although the profile of this magnetic system is not brand new, the novel way proposed in this paper to establish and manipulate such a system to fit versatile purposes has never been reported in the literature to the best of the authors' knowledge. The specific structure of the magnetic system should be optimized, starting from the immersive flow focusing mode together with the electron gun design, which will be determined on successful optimization. According to our analysis, such systems could be transformed into the Brillouin bunching mode by simply adjusting the coil currents without modifying the hardware. To verify such an approach, single-beam and multi-beam optical systems are demonstrated in this paper. Moreover, the beam radius in such systems could also be conveniently adjusted via a similar technique. [ABSTRACT FROM AUTHOR]

In this paper we report the reflection efficiency measurements of the VOXES Von Hamos (VH) spectrometer, based on HAPG mosaic crystals, together with ray tracing simulation results. Von Hamos spectrometers are widely used in several fields, ranging from fundamental physics to various practical applications. These types of Bragg spectrometers are usually used in high rate–high resolution experiments, where the typical source size can be as low as a few tens of microns. The VOXES collaboration at the INFN Laboratories of Frascati recently developed a VH spectrometer, making use of HAPG mosaic crystals and optimized X-ray beam optics, which could be used for source sizes up to a few mm in the Bragg plane and some tens of mm in the sagittal plane. Such a spectrometer may open a new era in the field of exotic (kaonic) atom precision measurements, delivering data with unprecedented precision to the nuclear physics community. In order to plan the use of this spectrometer the capabilities in terms of signal collection efficiency need to be checked, reliable ray tracing simulations have to be developed and consistency between data and simulations has to be verified. In this paper, we present this crosscheck for a ρ = 206.7 mm cylindrically bent HAPG crystal using CuKα1,2 and FeKα1,2 XRF lines. For both of them, the experimental results and the simulations are found to be in good agreement within the errors. [ABSTRACT FROM AUTHOR]

The mutual optical intensity (MOI) model is a partially coherent radiation propagation tool that can sequentially simulate beamline optics and provide beam intensity, local degree of coherence and phase distribution at any location along a beamline. This paper extends the MOI model to non-ideal two-dimensional (2D) optical systems, such as ellipsoidal and toroidal mirrors with 2D figure errors. Simulation results show that one can tune the trade-off between calculation efficiency and accuracy by varying the number of wavefront elements. The focal spot size of an ellipsoidal mirror calculated with 100 × 100 elements gives less than 0.4% deviation from that with 250 × 250 elements, and the computation speed is nearly two orders of magnitude faster. Effects of figure errors on 2D focusing are also demonstrated for a non-ideal ellipsoidal mirror and by comparing the toroidal and ellipsoidal mirrors. Finally, the MOI model is benchmarked against the multi-electron Synchrotron Radiation Workshop (SRW) code showing the model's high accuracy. [ABSTRACT FROM AUTHOR]

In traditional cesium beam clocks, cesium atoms are deflected by strong inhomogeneous magnetic fields. The distribution of the detectable atoms, which is critical to the short-term frequency stability, is hard to describe with analytical functions. In this paper, we numerically analyze the beam optics performance of cesium beam tubes based on the magnetic-state-selected and fluorescence detection scheme. To accurately model the cesium beam tube, we apply the Monte Carlo sampling directly inside the collimator. The finite element method is also applied to model the magnetic field. Upon the high dimensional distribution space, two key parameters are selected as indicators of the short-term performance of the cesium beam tube, the effective velocity distribution, and the normalized density difference of atoms in | F = 3 , m F = 0 ⟩ and | F = 4 , m F = 0 ⟩. The influence of the configuration of the collimator is analyzed. Experiments are carried out with two manufactured beam tubes. The results show good agreement with the simulation model. We also discuss limitations of the simulation method when applied to designing cesium beam tubes. [ABSTRACT FROM AUTHOR]

Traditional x-ray sources used today for multiple applications, such as medical imaging (computed tomography, radiography, mammography, and interventional radiology) or industrial inspection, are vacuum based electron beam devices that include several key components, such as electron emitters, electron guns/cathodes, and anodes/targets. The associated electronics for electron beam generation, focusing and control, and beam acceleration are located outside the vacuum chamber. The general topology of these tubes has been directionally unchanged for more than 100 years; however, tube design remains a long, inefficient, tedious, and complex process; blind design of experiments do not necessarily make the process more efficient. As a case study, in this paper, we introduce the differential evolution (DE), an artificial intelligence-based optimization algorithm, for the design optimization of x-ray source beam optics. Using a small-scale design problem, we demonstrate that DE can be an effective optimization method for x-ray source beam optics design. [ABSTRACT FROM AUTHOR]

Although laser scanning ideas and hardware solutions are well-known to experts in the field, there is still a large area for optimization. Especially, if long-range and high-resolution scanning is considered, the smallest defects in optical quality should be perfected. On the other hand, the simplicity, reliability, and finally the cost of the solution plays an important role, too. In this paper, a very simple but efficient method of optical correction is presented. It is dedicated to laser scanners operating from inside cylindrical glass domes. Such covers normally introduce aberrations into both the laser beam and receiving optics. If these effects are uncorrected, the laser scanner performance is degraded both in terms of angular resolution and maximum range of operation. It may not be critical for short-range scanning applications; however, if more challenging concepts are considered, this issue becomes crucial. The proposed method does not require sophisticated optical solutions based on aspheric or freeform components, which are frequently used for similar purposes in imaging-through-dome correction but is based on a simple cylindrical refractive correction plate. [ABSTRACT FROM AUTHOR]

Thermal diffusivity a and thermal conductivity λ are important parameters for many structural and functional material applications. These parameters determine the intensity of heat transfer, the quality of thermal insulation, the rate of heating/cooling, the efficiency of power equipment, as well as the possibility of reaching a stationary mode. In laser technologies, a and λ define the radiation resistance of the optical components of a system. In laser technologies involving material removal, these parameters determine the speed and quality of machining. At present, the majority of methods for measuring a and λ in solid materials require cutting out samples of a certain geometry, which makes such methods unsuitable for testing finished products. In this paper, we propose an express method for determining a and λ in translucent materials, which does not require cutting samples out of an object under inspection. This method implies registration and analysis of a nonstationary temperature field on the surface of a test object using a high-speed thermal imaging camera. An unsteady heating spot is created by a focused laser beam. The laser is operated in the mode of intermittent switching and continuous irradiation under constant intensity during the entire period of measurements. The heat propagated from this spot to the periphery forms a nonstationary temperature field, which contains information about a and λ. The a value is derived from the primary data using original algorithms and software. The dynamic temperature field is recorded by a thermal camera, a noncontact and high-speed device capable of processing a large amount of information (each of the many hundreds of thousands of pixels of a professional thermal imager matrix is a temperature sensor in a small surface area). The specifics of measuring thermal diffusivity a and thermal conductivity λ in translucent materials of laser beam optics is noted. Thus, the low radiation absorption coefficient and the possible curvature of the surface (for example, in lenses) require special measures. Due to the large amount of information contained in the dynamic patterns of thermal field and the possibility of averaging over a large data array, the RMS of the thermal diffusivity measurement does not exceed 2%. [ABSTRACT FROM AUTHOR]

Laser-assisted double-wire welding with a nontransferred arc is used for cladding workpieces. The wire material is melted by an arc and dropped onto the substrate, where a laser beam is oscillated by a galvanometer scanner to achieve bonding of the melt with good contact angles that do not result in undercuts. In this study, the galvanometer scanner was replaced by a beam shaping optics generating a line with a width of 1.2 mm and a length of 9.1 mm. Based on Design of Experiments, the laser power was varied in a range from 1500 to 2000 W and the welding speed in a range from 600 to 800 mm/min. Single weld beads of AISI 316L were welded onto a mild steel of AISI 1024 according to a full factorial design at three repetitions per parameter set. The paper examines whether the contact angles of the weld beads produced with the line optics are comparable to those obtained by oscillating the laser beam. In addition, the dilution of the material with the substrate was determined in micrographs. The results show that the bonding to the substrate can be achieved. The parameter window for the laser power with beam shaping line optics is different from that with the oscillated laser beam. The required laser power is 1.5–2 times greater. [ABSTRACT FROM AUTHOR]

SPIDER (Source for Production of Ion of Deuterium Extracted from RF plasma) is the full-size prototype of the negative ion source for future ITER neutral beam injectors. With a maximum acceleration voltage of 100 kV, a negative ion beam is extracted and accelerated, and different diagnostics are developed to characterize the performance, shape, and deflection of the beam as well as the width of the beamlets. In particular, the optics of the accelerated beam is studied with a set of 15 cameras installed all around the beam, and they measure the visible emission; the spatial profile of the emission gives an estimate of the beamlets that compose the beam and also information about its optics. In this paper, experiments performed in volume operation (without cesium) are analyzed, studying the role of the extraction and acceleration voltages, polarization of plasma grid and bias plate, and magnetic filter field. It is shown how the width of the beam is not spatially uniform. Two types of non-uniformity are pointed out: a top/bottom asymmetry at large spatial scale and a smaller one at the single driver scale. [ABSTRACT FROM AUTHOR]

This paper describes the beam transmission characteristics through the spiral inflector and in the central region of the K500 superconducting cyclotron at VECC due to solenoid magnet misalignment in its vertical injection line. The equations of motion for a particle in misaligned solenoidal channel are derived from the Hamiltonian and used to investigate the behaviour of the beam during injection where the axial magnetic field of the cyclotron plays an important role. We have optimised the solenoid strength in the vertical line to reduce transmission loss in the spiral inflector and to match the beam in the central region of the cyclotron. The percentage of the accepted particle in the spiral inflector and in the central region are calculated for different values of translational and rotational misaligned parameters of the solenoids. The allowed tolerances of these parameters are obtained to get the desired injection efficiency. [ABSTRACT FROM AUTHOR]

An adjustable radio frequency (RF) positive hydrogen ion source is designed in Huazhong University of Science and Technology (HUST) to provide ion beam with adaptive beam current and beam energy for neutral beam injection (NBI) related material research. The ion source aims to produce 10–20 keV positive hydrogen ion beam with total current of 50–125 mA. This paper investigates the design of the RF ion source including RF driver via inductively discharge mechanism and the extractor which is designed and optimized, including ion beam optics simulation, thermal analysis and power supply analysis. The vacuum analysis of the source is carried out as well. [ABSTRACT FROM AUTHOR]

Linear optics parameters are often estimated using turn-by-turn (TbT) data. In-plane beta functions, which are the most common measurement objectives, can be estimated from the amplitudes or phases of TbT data, providing an overall characterization of the linear lattice. In addition to estimating uncoupled Twiss parameters, TbT data can also be utilized for characterizing coupled linear motion. We investigate several methods for constructing a full normalization matrix at each beam position monitor (BPM). BPMs provide information on beam centroid transverse coordinates, but direct observation of transverse momenta is not available. To estimate momenta, one can use a pair of BPMs or fit data obtained from several BPMs. By using both coordinates and momenta, it is possible to fit the one-turn matrix (or its power) at each BPM, allowing for the computation of coupled Twiss parameters. Another approach involves the minimization of side peak amplitudes in the spectrum of normalized complex coordinates. Similarly, the normalization matrix can be estimated by fitting linear coupled invariants. In this study, we derive and utilize a special form of the normalization matrix, which remains non-singular in the zero coupling limit. Coupled Twiss parameters can be obtained from the normalization matrix. The paper presents the results of applying and comparing these methods to both modeled and measured VEPP-4M TbT data, demonstrating effective estimation of coupled Twiss parameters. [ABSTRACT FROM AUTHOR]

This study investigates the average signal-to-noise ratio $ \left\langle {\textrm{SNR}} \right\rangle $ ⟨ SNR ⟩ at the shot-noise limited receiver of an optical wireless communication system (OWC) that uses collimated Gaussian beam with adaptive optics correction in non-Kolmogorov weak turbulent atmosphere. $ \left\langle {\textrm{SNR}} \right\rangle $ ⟨ SNR ⟩ and the variation in the percentage $ \left\langle {\textrm{SNR}} \right\rangle $ ⟨ SNR ⟩ are calculated and the results are presented against various adaptive optics correction modes, non-Kolmogorov power-law exponent, receiver aperture size, Gaussian beam source size, photodetector quantum efficiency, electronic bandwidth, link length, and turbulence strength. Adaptive optics correction is analyzed for tilt, defocus, astigmatism, coma and trefoil modes and their variations. The effects of adaptive optics compensation are examined that cause an increase in SNR, hence improve the performance of an OWC system using collimated Gaussian beam and operating in the non-Kolmogorov weak turbulent atmosphere. [ABSTRACT FROM AUTHOR]

The intensities and phase profiles of the elliptic optics vortex beam both are determined by the topological charge (TC) and ellipticity. This paper presents an efficient and simple method for measuring the TC and ellipticity of elliptic vortex. By observing the diffraction patterns, the TC modulus and ellipticity can be probed with the suitable rectangular aperture, and the TC sign can be detected with the suitable right triangular aperture. The scheme works well even for high-order elliptic vortex with topological charge value as high as ± 18, and ellipticity range from 0.5 to 2 at least. Obviously, the measurement of TC and ellipticity have important research value for promoting the application of elliptical vortex. [ABSTRACT FROM AUTHOR]

The distributions of the k -th largest level at the soft edge scaling limit of Gaussian ensembles are some of the most important distributions in random matrix theory, and their numerical evaluation is a subject of great practical importance. One numerical method for evaluating the distributions uses the fact that they can be represented as Fredholm determinants involving the so-called Airy integral operator. When the spectrum of the integral operator is computed by discretizing it directly, the eigenvalues are known to at most absolute precision. Remarkably, the Airy integral operator is an example of a so-called bispectral operator, which admits a commuting differential operator that shares the same eigenfunctions. In this paper, we develop an efficient numerical algorithm for evaluating the eigendecomposition of the Airy integral operator to full relative precision, using the eigendecomposition of the commuting differential operator. This allows us to rapidly evaluate the distributions of the k -th largest level to full relative precision rapidly everywhere, except in the left tail, where they are computed to absolute precision. In addition, we characterize the eigenfunctions of the Airy integral operator, and describe their extremal properties in relation to an uncertainty principle involving the Airy transform. We observe that the Airy integral operator is fairly universal, and we describe a separate application to Airy beams in optics. [ABSTRACT FROM AUTHOR]

This paper studies the inhomogeneous nonlinear Schrödinger equations, which may model the propagation of laser beams in nonlinear optics. Using the cross‐constrained variational method, a sharp condition for global existence is derived. Then, by solving a variational problem, the strong instability of solitary waves of this equation is proved. [ABSTRACT FROM AUTHOR]

The High energy FRagment Separator (HFRS), a new generation in-flight radioactive separator, is under construction at the high-intensity Heavy Ion Accelerator Facility (HIAF) in China. To further optimize the separator performance and consider the manufacturing technology, the specifications of some magnetic elements of the HFRS separator have been modified from the original design reported earlier, and prototypes of partial magnetic elements have been fabricated and tested. In this paper, updates of magnetic parameters, test results of prototypes, and development of ion-optical calculation are presented. The high-order correction of aberrations is demonstrated. The performance of the separator is studied using fission reactions and fragmentation reactions of relativistic 238U projectiles. This work will guide the forthcoming experiments in the future HFRS separator. [ABSTRACT FROM AUTHOR]

Purpose: Intraoperative electron radiotherapy (IOeRT) is considered the first clinical translation of FLASH with electrons. A crucial aspect is represented by the precise dose monitoring and measurement; tothis aim, we propose a method fully based on Monte Carlo (MC) simulation that uses as input the beam current measurement and the beam optics simulation. To validate this approach, we chose the NOVAC11 (produced by Sordina IORT Technologies SpA) accelerator, which provides a well-studied model. Methods: We used FLUKA and FRED MC software to simulate in detail the geometry of the NOVAC11 and the coupled applicator usually adopted in clinical practice to deliver the dose in the surgical bed. The simulation results of the longitudinal and off-axis profiles and dose per pulse obtained in a water phantom with different applicators are compared to the experimental data. Results: A very good agreement not only for the relative dosimetry in both the longitudinal and off-axis profiles, with a gamma index pass rate of 100% with 3%/3 mm acceptance criteria, but also for the absolute dosimetry was obtained. Conclusion: The results completely validate the MC description of the system and provide a reliable evaluation of the dose per pulse and output factor with an accuracy of the order of few % for different sets of applicator diameters and lengths. [ABSTRACT FROM AUTHOR]

Fractional‐order vector vortex beams (VVBs) have recently been demonstrated as new carriers of fractional‐strength optical vortices. However, the inherent mechanism of the new vortex beams, formed by the combination of both unstable states, to propagate stably in free space requires clarification. In this study, this scientific problem is solved by revealing the physical essence of propagable fractional‐strength optical vortices in free space. Therefore, three new viewpoints regarding these unique vortex beams are proposed: Abbe's diffraction limit, the phase evolution of the vortex beam, and the binary time vector property of phase. First, due to Abbe's diffraction limit, the inherent polarization modes are intertwined, thereby maintaining the entire unique vortex beam in free space. In the second case, the phase evolution of the vortex beam is the physical cause for the polarization rotation of fractional‐order VVBs. Third, the phase is not merely a scalar attribute of the light beam and demonstrates a binary time vector property. This study provides entirely different physical viewpoints on the phase of the vortex beam and Abbe's diffraction limit, which may deepen the knowledge on the behavior of light beams in classical optics. [ABSTRACT FROM AUTHOR]

The ever increasing demands placed upon machine performance have resulted in the need for more comprehensive particle accelerator modeling. Computer simulations are key to the success of particle accelerators. Many aspects of particle accelerators rely on computer modeling at some point, sometimes requiring complex simulation tools and massively parallel supercomputing. Examples include the modeling of beams at extreme intensities and densities (toward the quantum degeneracy limit), and with ultra-fine control (down to the level of individual particles). In the future, adaptively tuned models might also be relied upon to provide beam measurements beyond the resolution of existing diagnostics. Much time and effort has been put into creating accelerator software tools, some of which are highly successful. However, there are also shortcomings such as the general inability of existing software to be easily modified to meet changing simulation needs. In this paper possible mitigating strategies are discussed for issues faced by the accelerator community as it endeavors to produce better and more comprehensive modeling tools. This includes lack of coordination between code developers, lack of standards to make codes portable and/or reusable, lack of documentation, among others.

An electron is a quantum particle and behaves as both a particle and a probability wave. On account of this it can be controlled in a similar way to a photon and electronic devices can be designed in analogy to those based on light when there is minimal excitation of the underlying Fermi sea. Here, splitting of the electron wavefunction is explored for systems supporting Dirac type physics, with a focus on graphene but being equally applicable to electronic states in topological insulators, liquid helium, and other systems described relativistically. Electron beam‐splitters and superfocusers are analysed along with propagation through nanoribbons, demonstrating that the waveform, system geometry, and energies all need to balance to maximise the probability density and hence lifetime of the flying electron. These findings form the basis for novel quantum electron optics. [ABSTRACT FROM AUTHOR]

A novel extraction system with variable grid gap has been developed for the Neutral Beam Injection (NBI) at ASDEX Upgrade to be able to adjust beam energy and power independently. The ASDEX Upgrade NBI is composed of two beamlines (one operating at 60 kV, one at 93 kV) with four ion sources each, delivering a total heating power up to 20 MW. To achieve low beam divergence which reduces transmission losses in the duct, the system has to be operated, like any NBI, at the perveance optimum Π opt which is proportional to I ext /U ext 3/2, (I ext = extracted current, U ext = extraction voltage). The extracted beam power P ext = I ext U ext = Π opt U ext 5/2 has therefore a strong dependence on the extraction voltage. If beam energies lower than the nominal values are required, the extracted current has to be reduced accordingly, leading to a drastic reduction of the heating power. The optimum perveance Π opt is specific for each extraction system and defined by its geometry, approximately by the ratio of the grid aperture diameter to the gap between the first and the second grid (extraction gap). We have developed an extraction system with a "variable gap" between those grids which can be changed in situ and remotely between shots. Varying this gap modifies Π opt which allows to set beam energy and beam current independently in a wide range while maintaining minimum divergence. This extends the operational space of NBI significantly and adds experimental versatility for ASDEX Upgrade. A conventional extraction grid system was modified while maintaining interchangeability with the existing systems and keeping the impact on beam optics minimal. The paper discusses the consequences of such variable gap for beam optics and describes the technical boundary conditions, the final design and prototype tests. [ABSTRACT FROM AUTHOR]

For CEPC LINAC, the first 80 MW class klystron at C-band (5720 MHz) has been proposed to accelerate a high-current beam at an acceleration gradient of 45 MV/m. This paper discusses the design and simulation of beam optics, beam envelope, drift tube, and solenoid of the klystron. Space charge beam current of 390 A at an acceleration potential of 410 kV is obtained with average cathode loading of less than 6.0 A/cm2. The maximum surface electric field at the beam optics and high voltage ceramic seal have been evaluated less than 22 kV/mm and 4.50 kV/mm, respectively. The electron beam with an average beam radius of 5.40 mm has successfully been transported to the interaction cavity with beam ripple rate around 4.0% with low scalloping factor and a fill factor of 0.670. 2-D, DGUN & POISSON simulations results are validated by the 3-D CST simulation and found in agreement. [ABSTRACT FROM AUTHOR]

Laser beam welding is a promising technology to enable automated high-quality welding procedures at significantly higher processing speeds compared to conventional processes. However, its usability is often limited by gap bridgability. This disadvantage is related to the small laser beam spot sizes that require low gap sizes for joining, which are often practically not available, and the desired welding without additional filler materials to enable high processing speeds without direction restrictions. New possibilities of beam shaping for process control are also available now for high-power laser processing and they show promising results. The resulting complex effects require additional investigation to understand the mechanisms and the use of the technologies for process improvements. Therefore, in this work, advanced beam shaping optics with up to four separate laser beam spots was used to understand the impact of multiple-spot welding on the process dynamics and gap bridgability. Gap bridgability was measured by an opening gap setup, while spatter amounts as indicators of process dynamics were measured by high-speed imaging. It was shown that multiple-spot laser welding can increase the gap bridgability, probably due to the initiated melt flow toward the joining partners. Symmetric separation of the keyholes toward the sheets increased the gap bridgability, while additional low-intensity spots in the center were able to stabilize the melt pool and reduce spattering. [ABSTRACT FROM AUTHOR]

The properties of electromagnetic undulators, produced by the field of a high-power microwave, are discussed. We analyze the conditions to be satisfied that allow the treatment of the emission process by relativistic charges moving through it in full analogy with the case of their static counterparts. We critically review the often claimed possibility of exploiting them in programs aimed at reducing the sizes and costs of an actual free electron laser (FEL) device. We analyze several possible configurations for FELs based on powerful microwave undulators and conclude that the present level of technology, even though not yet mature, should be improved to allow a breakthrough either for low- or high-gain devices. [ABSTRACT FROM AUTHOR]

The self-consistent nonlinear dynamics of a relativistic charged particle beam interacting with its complete self-fields is a fundamental problem underpinning many of the accelerator design issues in high brightness beam applications, as well as the development of advanced accelerators. Particularly, synchrotron radiation induced effects in a magnetic dispersive beamline element can lead to collective beam instabilities and emittance growth. A novel beam dynamics code is developed based on a Lagrangian method for the calculation of the particles' radiation near-fields using wavefront/wavelet meshes via the Green's function of the Maxwell equations. These fields are then interpolated onto a moving mesh for dynamic update of the beam. This method allows radiation co-propagation and self-consistent interaction with the beam in 2D/3D simulations at greatly reduced numerical errors. Multiple levels of parallelisms are inherent in this method and implemented in our code CoSyR to enable at-scale simulations of nonlinear beam dynamics on modern computing platforms using MPI, multi-threading, and GPUs. The current 2D implementation of CoSyR has been used to evaluate the transverse and longitudinal coherent radiation effects on the beam and to investigate beam optics designs proposed for mitigation of beam brightness degradation in a magnetic bunch compressor. In this paper, the design of CoSyR, as well as the benchmark with other coherent synchrotron radiation models, are described and discussed. Extension of the core algorithms to 3D is possible and planned. [ABSTRACT FROM AUTHOR]

A Geant4 simulation code was developed to perform realistic simulations of the RIBRAS facility. A second-order expansion of a finite solenoid field was included to describe the beam optics with good precision. A systematic study of coil currents for several magnetic rigidities and focal points was performed. Parameterizations of the coil currents for single and dual mode operations were obtained. Dedicated routines were developed to simulate the mechanism of direct reactions involving two and three particles in the final state. The present simulations were employed to investigate the feasibility of a Solenoidal Spectrometer with the RIBRAS facility. Our first results indicate that the concept can be applied in the RIBRAS system under certain conditions. Forthcoming studies both from simulations and experiments are already under development. [ABSTRACT FROM AUTHOR]

A beam optics study using the ITER-relevant high intense negative ion beams, such as 1 MeV, 200 A/m2, has been performed experimentally and analytically using a multi-aperture and five-stage accelerator. Initially, multi-beamlets generated from this accelerator were deflected in various directions due to the magnetic field and space charge repulsion between beams and showed various divergences. These had limited the pulse length and the beam energy. Compensation methods of the beamlet deflections have worked effectively and contributed to achieving the ITER requirement, the divergence angle of <7 mrad, and the deflection angle of <1 mrad for 1 MeV beam. The beam pulse has been gradually extended from 1 to 100 s and is now going to a longer pulse based on these results. One of the remaining issues is to understand and suppress peripheral components of the beam, namely, the halo, and to reduce the local heat loads observed around the aperture edge. This halo component has been successfully distinguished from the beam core by using a newly developed beam emittance measurement system for high intense beams. By combining this measured beam emittance and the beam simulation, it was clarified for the first time that the halo components are generated in an area of 1 mm width from the aperture edge. [ABSTRACT FROM AUTHOR]

Purpose: In proton therapy, the gantry, as the final part of the beamline, has a major effect on beam intensity and beam size at the isocenter. Most of the conventional beam optics of cyclotron‐based proton gantries have been designed with an imaging factor between 1 and 2 from the coupling point (CP) at the gantry entrance to the isocenter (patient location) meaning that to achieve a clinically desirable (small) beam size at isocenter, a small beam size is also required at the CP. Here we will show that such imaging factors are limiting the emittance which can be transported through the gantry. We, therefore, propose the use of large beam size and low divergence beam at the CP along with an imaging factor of 0.5 (2:1) in a new design of gantry beam optics to achieve substantial improvements in transmission and thus increase beam intensity at the isocenter. Methods: The beam optics of our gantry have been re‐designed to transport higher emittance without the need of any mechanical modifications to the gantry beamline. The beam optics has been designed using TRANSPORT, with the resulting transmissions being calculated using Monte Carlo simulations (BDSIM code). Finally, the new beam optics have been tested with measurements performed on our Gantry 2 at PSI. Results: With the new beam optics, we could maximize transmission through the gantry for a fixed emittance value. Additionally, we could transport almost four times higher emittance through the gantry compared to conventional optics, whilst achieving good transmissions through the gantry (>50%) with no increased losses in the gantry. As such, the overall transmission (cyclotron to isocenter) can be increased by almost a factor of 6 for low energies. Additionally, the point‐to‐point imaging inherent to the optics allows adjustment of the beam size at the isocenter by simply changing the beam size at the CP. Conclusion: We have developed a new gantry beam optics which, by selecting a large beam size and low divergence at the gantry entrance and using an imaging factor of 0.5 (2:1), increases the emittance acceptance of the gantry, leading to a substantial increase in beam intensity at low energies. We expect that this approach could easily be adapted for most types of existing gantries. [ABSTRACT FROM AUTHOR]

CYRCé is a TR24 cyclotron installed at the Institut Pluridisciplinaire Hubert Curien (IPHC) of Strasbourg operating at energies of 16–25 MeV and at intensities up to 400 μ A. The accelerator is used to produce and provide radio-elements for PET and for SPECT. In 2015, IPHC started to develop a platform with the aim of performing radiobiological experiments. The PRECy platform foresees to contain three-to-five experimental stations linked to beamlines expanded from the second exit port of the cyclotron. This extension allows devoting one of the beamlines for detector studies within the framework of the CMS project. The design, the development and the commissioning of the first two beamlines are discussed in this paper. [ABSTRACT FROM AUTHOR]

The third-order structure resonance due to sextupole magnetic fields was compensated in the Japan Proton Accelerator Research Complex main ring synchrotron using new beam optics. In the present optics, the third-order structure resonance ν x − 2ν y = −21 was so strong that the working point was limited. The new optics cancels the resonance by adjusting the phase advances in the arc sections. The resonance compensation was verified by aperture survey simulations and further demonstrated by three types of experiment. First, transverse coupling measurements were performed. The coupling was observed only for the optics without the compensation. This was also verified with the tracking simulation. Second, beam losses were measured using the current and new optics. The measured beam losses were noticeably reduced at the tunes around the resonance using the new optics. The beam loss reduction was also verified with the space charge tracking simulation. Third, Fourier analyses of the transverse dipole oscillations were conducted for both optics. Fourier spectra derived from the resonances were observed, and their peaks were clearly suppressed with the new optics. This was also consistent with the results of the space charge simulations. [ABSTRACT FROM AUTHOR]

Gantry is an indispensable part in the proton therapy facility to achieve multi-angle radiations. The introduction of superconducting techniques can significantly reduce the weight and volume of the gantry. A superconducting gantry with large momentum acceptance is under study at Huazhong University of Science and Technology. The first and second-order beam optics design has been accomplished. To narrow down the difference between optics design and beam tracking result in real magnetic fields, the high order optics optimization shall be performed. It is a many-objective optimization problem, and many knobs need to be fitted. The traditional fitting method in beam optics codes (e.g. MAD-X, TRANSPORT) is difficult to perform an efficient search in a large parameter space. This paper proposes an optimization approach based on the genetic algorithm NSGA-III for the high order optics of the superconducting gantry. Instead of the matrix coefficients fitting in the first and second-order optics design, the beam size and its symmetry in two planes are identified as the objectives. After the optimization with 1000 generations, a stable round beam can be achieved at the treatment terminal and the momentum acceptance reaches −6%/＋7% in the fifth-order optics. [ABSTRACT FROM AUTHOR]

Purpose: In proton therapy, the potential of using high‐dose rates in the cancer treatment is being explored. High‐dose rates could improve efficiency and throughput in standard clinical practice, allow efficient utilization of motion mitigation techniques for moving targets, and potentially enhance normal tissue sparing due to the so‐called FLASH effect. However, high‐dose rates are difficult to reach when lower energy beams are applied in cyclotron‐based proton therapy facilities, because they result in large beam sizes and divergences downstream of the degrader, incurring large losses from the cyclotron to the patient position (isocenter). In current facilities, the emittance after the degrader is reduced using circular collimators; however, this does not provide an optimal matching to the acceptance of the following beamline, causing a low transmission for these energies. We, therefore, propose to use a collimation system, asymmetric in both beam size and divergence, resulting in symmetric emittance in both beam transverse planes as required for a gantry system. This new emittance selection, together with a new optics design for the following beamline and gantry, allows a better matching to the beamline acceptance and an improvement of the transmission. Methods: We implemented a custom method to design the collimator sizes and shape required to select high emittance, to be transported by the following beamline using new beam optics (designed with TRANSPORT) to maximize acceptance matching. For predicting the transmission in the new configuration (new collimators + optics), we used Monte Carlo simulations implemented in BDSIM, implementing a model of PSI Gantry 2 which we benchmarked against measurements taken in the current clinical scenario (circular collimators + clinical optics). Results: From the BDSIM simulations, we found that the new collimator system and matching beam optics results in an overall transmission from the cyclotron to the isocenter for a 70 MeV beam of 0.72%. This is an improvement of almost a factor of 6 over the current clinical performance (0.13% transmission). The new optics satisfies clinical beam requirements at the isocenter. Conclusions: We developed a new emittance collimation system for PSI's PROSCAN beamline which, by carefully selecting beam size and divergence asymmetrically, increases the beam transmission for low‐energy beams in current state‐of‐the‐art cyclotron‐based proton therapy gantries. With these improvements, we could predict almost 1% transmission for low‐energy beams at PSI's Gantry 2. Such a system could easily be implemented in facilities interested in increasing dose rates for efficient motion mitigation and FLASH experiments alike. [ABSTRACT FROM AUTHOR]

We report the instrumentation of a new positron diffractometer that is connected to the high-intensity positron beam at the neutron induced positron source Munich. Crucial elements for the adaption of the positron beam are presented, which include the magnetic field termination, the optional transmission-type remoderator for brightness enhancement, and the electrostatic system for acceleration and beam optics. The positron trajectories of the remoderated and the twofold remoderated beam have been simulated to optimize the system, i.e., to obtain a coherent beam of small diameter. Within a first beamtime, we tuned the system and characterized the direct beam. For the twofold remoderated beam of 10 keV energy, we experimentally observe a beam diameter of d < 1.3 mm, which agrees well with the simulation. [ABSTRACT FROM AUTHOR]

An instrument is demonstrated that is capable of simultaneous and independent flow density fluctuation measurements over the same line-of-sight by combining two optical techniques: focused laser differential interferometry (FLDI) and high-speed schlieren (HSS). The FLDI instrument measures fluctuations at a single point in the flowfield at 10 MHz, with the resulting signal most sensitive in the region nearest the focal plane of the FLDI laser beam. The HSS instrument acquires images at 20 kHz along the same optical axis as the FLDI beam, but with the resulting signal path averaged over the entire HSS line-of-sight. The introduction of the HSS optics into the FLDI beam path provides two high-quality measurement capabilities in a single system with no degradation of performance relative to stand-alone FLDI or HSS instruments. [ABSTRACT FROM AUTHOR]

We report on Line Beam Optics operated by multiplexing of high power pulsed 343nm solid state lasers for crystallization of a‐Si films on OLED backplanes. Specific properties of the optical system are described. The temporal polarization control and pulse duration setting improves the uniformity of the crystallized a‐Si film. The CoO (cost of ownership) reduction compared to the current ELA‐process is obtained by using diode‐pumped solid lasers which offer low maintenance, long lasting third harmonic optics and operation by electrical power, water cooling and purge air only. [ABSTRACT FROM AUTHOR]