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Lasers with average powers of several kilowatts have become an important tool for industrial applications. Temporal and spatial beam shaping was demonstrated to improve existing and enable novel applications. A very promising technology for both highly dynamic beam shaping and power scaling is the coherent combining of the beams of an array of high-power fundamental mode fibers. However, the limited number of fibers allows only limited spatial resolution of the common phase front. It is therefore favorable to work with plane or spherical common phase fronts, which generate a “point”, i.e., a diffraction pattern with a strong main lobe in the focal plane. By applying a tilt to the common phase front, points can be positioned in the focal plane with high spatial resolution. The Civan DBL 6–14 kW investigated in this work allows switching between positions of the points with 80 MHz. Sequences of points can be used to create arbitrary shapes. The time constants of points and shapes are very critical for this type of shape generation. The current paper analyzes the relevant time constants for setting points and creating shapes and relates them to time constants in laser processes. This is mandatory to deterministically influence laser processes.

We discuss our experiences with developing detailed theoretical descriptions of intrabeam scattering in particle accelerators. We focus on the historical importance of understanding intrabeam scattering for the successful operation of a variety of accelerators around the world. In doing so, we highlight the fact that the theoretical understanding of intrabeam scattering played a crucial role in the discovery of the top quark at Fermilab, intermediate vector bosonsW±, Z and the Higgs particle at CERN, and the perfect liquid quark-gluon plasma at Brookhaven’s Relativistic Heavy Ion Collider. We describe several useful high energy approximations to intrabeam scattering, including those that utilize a Modified Piwinski high energy approximation by Karl Bane that has gained wide usage in applications to electron damping rings and advanced light sources. Finally, we comment on the fact that a detailed understanding of intrabeam scattering at synchrotron-based advanced light sources is empowering many transformational discoveries in a myriad of disciplines.

This paper reports the observation of beam energy widening and distortion from Gaussian due to a nonvanishing horizontal chromaticity at a quasi-isochronous storage ring. The result originates from an average path-length dependence on the betatron oscillation amplitudes, which is intimately correlated to the transverse chromaticities. It is the first experimental validation of the impact of such a nonlinear transverse-longitudinal coupling effect on the equilibrium beam characteristics in a storage ring. The results could be important for quasi-isochronous rings, steady-state microbunching, nonscaling fixed-field alternate gradient accelerators, etc., where very small momentum compaction or large chromaticity is required.

Dynamic beam shaping opens new possibilities for improving the quality and productivity of industrial laser material processing applications such as welding and cutting. However, dynamic beam shaping involves time constants and frequencies that must be selected correctly to successfully modify a given laser process. This paper proposes a standardized nomenclature for the possible types of dynamic beam shaping and the resulting dynamic process modifications, and relates these to characteristic time constants and frequencies at which the process modifications have a particularly strong influence on the process. These characteristic frequencies define three process regimes that have distinctly different effects on the process. An overview of typical time constants and frequencies in laser processes aids in understanding the occurrence of characteristic frequencies. Knowledge of the process regimes allows for a systematic selection of frequencies in dynamic beam shaping to achieve targeted dynamic process modifications, e.g., for pore reduction. Using a laser system capable of dynamic beam shaping at frequencies of up to 80 MHz, the influence of the three process zones on the porosity of the weld was demonstrated using deep welds in cast aluminum as an example.

For a Megawatt class accelerator, classical safety measures may not be sufficient. Precise knowledge of beam loss location and power deposition in the most various scenarios is crucial for the definition of appropriate protection systems. In this work, the case of the Linear IFMIF Prototype Accelerator is studied, where, due to its very high continuous wave beam intensity, the high power part concerns almost the whole accelerator. Beam dynamics simulations are performed to allow the ability to estimate beam losses in all the different situations of the accelerator lifetime: starting from scratch, beam commissioning, tuning or exploration, routine operation, sudden failures. All the results of these studies are given, establishing the catalogue of losses. Recommendations for hot point protection, beam stop speed, beam power limitation are given accordingly.

The technique of microbunched electron cooling (MBEC) is a coherent cooling scheme with possible applications in high-energy hadron and electron-ion machines. In our previous work we analyzed the cooling of the hadron energy spread and transverse emittance using a one-dimensional (1D) technique that tracked the microscopic fluctuations in the hadron and electron beams. However, in order to obtain analytical expressions for our key quantities, we limited ourselves to calculating and optimizing only the initial values of the cooling rates. In this paper, we extend our approach so that it properly addresses the issue of the long-term, dynamic evolution of the hadron beam. In order to do so, it becomes necessary to consider the synchrotron motion of the hadron beam, in conjunction with the effects of diffusion and intrabeam scattering (IBS). With these modifications, our formalism allows us to develop a simple numerical tool that can effectively model the final state of hadron beam after many passages through the MBEC cooler.

Particle accelerators are essential tools for scientific research in fields as diverse as high energy physics, materials science and structural biology. They are also widely used in industry and medicine. Producing the optimum design and achieving the best performance for an accelerator depends on a detailed understanding of many (often complex and sometimes subtle) effects that determine the properties and behavior of the particle beam. Beam Dynamics in High Energy Particle Accelerators provides an introduction to the concepts underlying accelerator beam line design and analysis, taking an approach that emphasizes the elegance of the subject and leads into the development of a range of powerful techniques for understanding and modeling charged particle beams.

Beam energy compression via chicane magnets has been proved to be an effective method to reduce the slice energy spread of electron beams generated by laser wakefield accelerators (LWFAs). This technique has been widely adopted by leading research teams in experiments targeting future compact, high-gain free electron lasers (FELs). However, after energy compression, a strong beam energy chirp is introduced into the electron beam, which substantially hinders the microbunching process and impairs spectral coherence. Here, we present a detailed, unaveraged three-dimensional simulation that examines the effects of this energy chirp, and the results can be applied to the design of a proposed LWFA-driven VUV FEL. The energy chirp in a LWFA-produced electron beam causes FEL interactions at multiple resonant frequencies across the entire electron bunch, simultaneously, which prevents sustained radiation power growth at the designed frequency along the undulator. Consequently, spectral purity is significantly degraded. Additionally, due to undulator dispersion, the energy chirp leads to an elongation of the bunch length, which increases microbunch separation. This results in a noticeable redshift in the radiation frequency and further disruption of spectral purity. These effects are compared to the ideal scenario in which the energy chirp is removed following energy compression. Simulation results indicate that the implementation of a beam dechirper is a crucial step for improving the saturation of radiation power. Insights gained from this simulation of energy chirp-induced mechanisms will aid in the development of more effective compensation strategies, ultimately optimizing LWFA-driven FEL designs.

Free-electron lasers (FELs) are a unique source of light, particularly in the x-ray domain. After the success of FELs based on conventional acceleration using radio-frequency cavities, an important challenge is the development of FELs based on electron bunching accelerated by a laser wakefield accelerator (LWFA). However, the present LWFA electron bunch properties do not permit use directly for a significant FEL amplification. It is known that longitudinal decompression of electron beams delivered by state-of-the-art LWFA eases the FEL process. We propose here a second order transverse beam manipulation turning the large inherent transverse chromatic emittances of LWFA beams into direct FEL gain advantage. Numerical simulations are presented showing that this beam manipulation can further enhance by orders of magnitude the peak power of the radiation.

We show the design results of beam dynamics on the injector for high-intensity proton accelerators. The injector can be utilized in a medical proton linac and accelerator driven system. The injector system consists of a 325-MHz RFQ (radio-frequency quadrupole) accelerator and a 325-MHz DTL (drift tube linac) accelerator. The injector has been designed to optimize the beam parameters to meet the required design goals. In this paper, we present a design study on the beam dynamics in the injector through beam tracking. We show the results of the beam dynamics study and cavity design study in the RFQ. The high-intensity RFQ accelerates the proton beam from 50 keV to 3 MeV with a peak beam current of 30 mA. The RFQ has a length of 3.839 m and Kilpatrick value of 1.76. We investigated ways to minimize the emittance growth caused by the space-charge effect and optimized achieve a high transmission and a small growth of emittance along the RFQ. The DTL with face angles of 3 degree and 10 degree in one tank accelerates proton beams from 3 MeV to 10 MeV and is 4.3 m long. Electromagnet quadrupoles (EMQs) are used as focusing elements in a Focusing-Defocusing-Focusing-Defocusing (FFDD) lattice scheme in the DTL. A quadrupole between the RFQ and the DTL, and 8 drift tubes (DT) in DTL are used for transverse matching in the DTL. We investigated the beam dynamics to achieve a high transmission and a small growth of emittance along the DTL. We also show the results of beam tracking simulations in the DTL. Our studies show that major parameters affecting on beam dynamics in the injector for a high-intensity proton linac are available.