Average Beam Power Research Articles

CFD Investigations on Heavy Liquid Metal Alternative Target Design for the SPS Beam Dump Facility

This study introduces numerical advancements in an alternative design for the Super Proton Synchrotron (SPS) Beam Dump Facility (BDF) at the European Laboratory for Particle Physics (CERN). The design envisions a high-power operation target made of flowing liquid lead. The proposed BDF is a versatile facility for both beam-dump-like and fixed-target experiments. The target behavior is studied, assuming a proton beam with a momentum of 400 GeV/c, a pulse frequency of 1/7.2 Hz, and an average beam power of 355 kW. Using various Computational Fluid Dynamics (CFD) codes, we evaluate the behavior of liquid lead and predict the thermal stress on the target vessel induced by the pulsed heat source generated by the charged particle beam. The comparison increases the reliability of the results, investigating the dependencies on the CFD modeling approach. The beam is a volumetric heat source with data from the beam-lead interaction simulations provided by the European Laboratory for Particle Physics and obtained with a Monte Carlo code. Velocity field and stress profiles can enhance the design of the lead loop and verify its viability and safety when operated with a liquid metal target.

Design and early operation of a new-generation internal beam dump for CERN’s Super Proton Synchrotron

The Super Proton Synchrotron (SPS) is the last stage in the injector chain for CERN’s Large Hadron Collider, and it also provides proton and ion beams for several fixed-target experiments. The SPS has been in operation since 1976, and it has been upgraded over the years. For the SPS to operate safely, its internal beam dump must be able to repeatedly absorb the energy of the circulating beams without sustaining damage that would affect its function. The latest upgrades of the SPS led to the requirement for its beam dump to absorb proton beams with a momentum spectrum from 14 to 450 GeV/c and an average beam power of up to ∼270 kW. This paper presents the technical details of a new design of the SPS beam dump that was installed in one of the long straight sections of the SPS during the 2019–2020 shutdown of CERN’s accelerator complex within the framework of the Large Hadron Collider Injectors Upgrade Project. This new beam dump has been in the operation since May 2021, and it is foreseen that it will operate with a lifetime of 20 years. The key challenges in the design of the beam dump were linked to the high levels of thermal energy to be dissipated—to avoid overheating and damage to the beam dump itself—and high induced levels of radiation, which have implications for personnel access to monitor the beam dump and repair any problems occurring during operation. The design process, therefore, included extensive thermomechanical finite-element simulations of the beam-dump core and its cooling system’s response to normal operation and worst-case scenarios for beam dumping. To ensure high thermal conductivity between the beam-dump core and its water-cooling system, hot isostatic pressing techniques were used in its manufacturing process. A comprehensive set of instrumentation was installed in the beam dump to monitor it during operation and to cross-check the numerical models with operational feedback. The beam dump and its infrastructure design were also optimized to ensure it can be maintained, repaired, or replaced while minimizing the radiation doses received by personnel. Published by the American Physical Society 2024

Wide-aperture Faraday Cup for the High-Intensity Linear Proton Accelerator of the Project DARIA

One of the main problems for beam diagnostics in the projected linear proton accelerator for the DARIA compact neutron source is the high pulse and average beam power combined with a relatively low energy, that significantly limits the choice of possible diagnostic instruments and methods. For basic beam current measurements and tuning procedures in the low-energy part of the accelerator, a wide-aperture water-cooled Faraday cup was developed. This paper presents design features, estimations of thermal loads during typical operation and experimental results of the cup tests at a high-intensity proton beam, also the design features of such devices are described, considering the influence of the beam space charge on the measurement results.

450 W pulsed laser system with M2 < 1.2 based on a 969-nm laser diode end-pumped Yb:YAG rod amplifier.

We demonstrated a compact and power-efficient multi-stage pulsed end-pumped amplifier with stabilized output power of 450 W and near-diffraction-limited beam quality (M2 < 1.2) at a repetition rate of 1 MHz. The pulsed amplifier produced an exceptional average power and optimal beam quality achieved in laser diode (LD) end-pumped Yb:YAG thin rod configuration at room temperature. A preliminary pulse compression with a chirped volume Bragg grating (CVBG) was performed reducing pulse duration to ∼730 fs at a compression efficiency of 90%. With the combined features, including compactness, reliability, and efficiency, of the end-pumped scheme, the demonstrated laser system would be of great value in both industry and scientific research.

High Average Power Green Laser Based on LED-Side-Pumped Q-Switched Nd:YAG Laser

In this paper, we demonstrated a watt-level acousto-optic (A-O) Q-switched intracavity frequency-doubled green laser with high average power and beam quality operation based on an efficient LED-pumped Nd:YAG laser module. For the quasi-continuous wave (QCW) running operation, the average output power of fundamental laser at 1064 nm was as high as 10.3 W at a repetition rate of 100 Hz, corresponding to the highest optical conversion efficiency of 25.4% and a slope efficiency of 31.3%, and the maximum energy of single pulse was up to 100mJ. By optimizing the incidence angle of the KTP crystal to meet the non-critical phase matching condition, greater than 3.8 W of 532 nm average power at a repetition rate of 10 kHz was generated with duration of 192 ns and a beam quality factor of M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 1.6 and M <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> = 1.7, corresponding to a frequency doubling conversion efficiency of 45.5%. To the best of our ability, this is the highest average power and high beam quality of an LED-pumped A-O Q-switched intracavity frequency-doubled green laser with watt-level output reported so far.

Review of High Average Power and High Beam Quality LD-Pumped Ytterbium-Doped Fiber Laser Oscillators and Amplifiers

Review of High Average Power and High Beam Quality LD-Pumped Ytterbium-Doped Fiber Laser Oscillators and Amplifiers

178-W picosecond green laser with active beam-pointing stabilization

Picosecond lasers with high average power and high beam quality have been widely used for precision processing and space exploration. In this study, we report a high-power picosecond green laser using a multistage Yb-doped rod-shaped photonic crystal fiber as an amplifier combined with a beam combination. The single amplification module achieves a 1,030 nm laser output of 146.8 W, and the maximum second harmonic generation (SHG) power is 92 W with a frequency conversion efficiency of 63.5%. The combined beam of the two SHGs resulted in a final output of 178 W with a repetition frequency of 24.07 MHz, pulse width of 50.1 ps, and beam quality factor of M2 = 1.16. Furthermore, an adaptive filter control method of a two-axis fast-steering mirror was applied to suppress the beam jitter to up to 45 Hz.

Rhodotron and rotating target: A solution towards micro-spot for high energy and high dose rate bremsstrahlung sources

High energy over MeV bremsstrahlung sources that employ normal conducting radio frequency linear accelerators have expanding applications in industrial computerized tomography (CT) for non-destructive inspection and evaluation. The X-ray spot size that mainly affects the imaging quality is yet limited by the electron beam width in the high resolution CT systems. In a short exposure time, high beam power is required to generate sufficient photons to improve the signal to noise ratio of imaging. However, with ∼kW level of average beam power these linear accelerators usually have a beam spot size over 1 mm since the temperature rising due to the beam energy deposition in the target should be far below its melting point. We propose a concept of using a Rhodotron-based accelerator to provide high power electron beams in a long duration pulse and a rotating target to mitigate the overheating issue, such that the gap between micro-spot and high dose rate can be bridged in the high energy bremsstrahlung sources. This article presents an in-depth simulation work to discuss and evaluate this scheme of X-ray source. The simulations of beam dynamics in the accelerator and bremsstrahlung process in the target predict the generated X-rays with a spot size as small as 68 μm at full-width half-maximum and a dose rate as high as 4700 cGy/min from a 9 MeV electron beam interacting with a 1 mm thickness tantalum target. Further thermal analysis in the rotating target indicates a significant improvement of beam power handling in comparison with the conventional stationary one.

Investigations on the Specifics of Laser Power Modulation in Laser Beam Welding of Round Bars

Welding round bars of large diameters in a rotational laser beam welding process corresponds with weld pool bulging and the risk of weld defects. Power modulation is a promising approach for bulge reduction and for keyhole stabilisation to achieve superior weld quality. The following investigations are about the specific effects of power modulation for round bars with a diameter of 30 mm. The welding speed is 0.95 m/min and argon is used as shielding and process gas. Triangle shaped power modulation at 8 kW average laser beam power, 0/2/4/6 kW amplitude power and 2/10/50 Hz modulation frequency is used for the round bar welding of a 1.4301 steel alloy. The welds are evaluated by visual inspection, metallographic cross sections and scanning acoustic microscopy. The amount of weld defects increases at medium and high power modulation, but weld pool bulging is already reduced at low power modulation. Weld pool bulging can be impeded by a low normalised power modulation frequency of 0.05 and a high modulation depth of 0.86. The power modulation’s advantages of weld mixing and degassing do not apply to rotational round bar welding because of the linear welding speed’s gradient from the specimen surface to the centre.

Through Over-Clad Inscription of FBG in CYTOP Optical Fiber Using Phase Mask Technique and 400 nm Femtosecond Pulsed Laser

In this work, we report the inscription of fiber Bragg grating through the over-clad in cyclic transparent fluoropolymer (CYTOP) optical fiber using a phase mask technique and a 400 nm femtosecond pulsed laser. 8 mm-long grating were obtained in less than 20 s with 500 <inline-formula><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>W average beam power. To investigate the FBG properties and discriminate between the protective over-clad influence and the core-cladding effect, we inscribe FBGs in the fiber with and without the over-clad. We also show that the temperature sensitivity of CYTOP-FBGs with the over-clad depends on the relative humidity, whereas CYTOP-FBGs without the over-clad achieve almost zero sensitivity to humidity and sensitivity to temperature of 26.7 pm/<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>C.

Design of a 10 MeV, 1000 kW average power electron-beam accelerator for wastewater treatment applications

We present the technical and engineering design of a medium energy (10 MeV) and high average power (1000 kW) electron-beam accelerator intended for irradiation treatment of high-volume industrial and municipal wastewater. The accelerator uses a ${\mathrm{Nb}}_{3}\mathrm{Sn}$ superconducting radio-frequency (SRF) cavity for producing the high average beam power with $&gt;90%$ rf to beam efficiency. The design of the accelerator is tailored for industrial settings by adopting the cryocooler conduction-cooling technique for the SRF cavity instead of a conventional liquid helium bath cryosystem. The technical design is supplemented with a detailed analysis of capital and operating cost of the accelerator. The designed accelerator can treat up to 12 million gallons per day of wastewater, requires capital of $\ensuremath{\sim}$8\text{ }\text{ }\mathrm{M}$ for construction, and has $\ensuremath{\sim}13.5\text{ }\text{ }\textcent{}/\mathrm{ton}/\mathrm{kGy}$ in material processing cost.

Possible solution for the integer resonance crossing problem of GeV-class isochronous Fixed-Field Alternating Gradient accelerators

Fixed-Field Alternating Gradient accelerators (FFAG, also known as FFA) are promising candidates for next-generation GeV-class proton driver with average beam power of several megawatts. In isochronous accelerators, radial tunes are approximately increasing with beam energy in a linear way, and thus the integer resonance crossing problem becomes the major bottleneck of GeV-class isochronous FFAG design. In 2019, China Institute of Atomic Energy (CIAE) proposed an isochronous FFAG conceptual design with capability of producing 2GeV/6MW continuous wave (CW) proton beam. However, this conceptual design shows that the beam size is blown up at high energy region due to the third harmonic magnetic field caused by imperfections. The reason is that the integer resonance vr=3 causes a large coherent oscillation, and this large amplitude is not compatible with the following third order intrinsic resonance 3vr=10. In order to correct the large coherent motion before reaching the 3vr=10 resonance, we propose an idea of integer resonance suppressor (IRS) which intentionally introduces the third harmonic magnetic field. Our calculation shows that third harmonic field of 10Gs is acceptable with proper IRS settings, meaning that the requirements of magnet manufacture and installation can be relaxed. The increased imperfection tolerances will make magnet manufacture and installation much easier.

Thermo-optical numerical modal analysis of multicore fibers for high power lasers and amplifiers

Lasers for modern industrial and research applications are required to provide a high average beam power and at the same time be reliable, efficient, and compact. Rare-earth doped single-mode fiber lasers are the most promising solution. Large mode area fibers are effectively used to reduce nonlinear effects and scaling up the beam power which is now bounded by thermal effects. A new cutting-edge approach to the issue involves the use of Multi-Core Fibers (MCFs), coherently combining several lower power beams into a higher power one, and thus pushing the threshold of nonlinearities and transverse mode instabilities to higher power. The amplification process involves heat generation in the doped cores due to quantum defect, which propagates radially and creates a temperature gradient across the fiber cross-section. Even though the cores are optically uncoupled, the refractive index gradient due to thermo-optical effects could cause cross-talk and core mode coupling. In this work, we numerically analyze the performances of 9-core MCFs for high power fiber lasers by taking into account the coupling and bending effects due to the heat load generated by the quantum defect between pump and laser radiation. MCFs show very low sensitivity to heat load and bending, with effectively single-mode behaviour up to 15 μm core diameter (effective area 181 μm2) and down to 35 μm pitch.

1.53 W all-solid-state nanosecond pulsed mid-infrared laser at 6.45 µm.

A compact and robust all-solid-state mid-infrared (MIR) laser at 6.45 µm with high average output power and near-Gaussian beam quality is demonstrated. A maximum output power of 1.53 W with a pulse width of approximately 42 ns at 10 kHz is achieved using a ZnGeP2 (ZGP) optical parametric oscillator (OPO). This is the highest average power at 6.45 µm of any all-solid-state laser to the best of our knowledge. The average beam quality factor is measured to be M2 = 1.19. Moreover, high output power stability is confirmed, with a power fluctuation of less than 1.35% rms over 2 h, and the laser can run efficiently for more than 500 h in total. Using this 6.45 µm pulse as a radiation source, ablation of animal brain tissue is tested. Furthermore, the collateral damage effect is theoretically analyzed for the first time, to the best of our knowledge, and the results indicate that this MIR laser has excellent ablation ability, making it a potential replacement for free electron lasers.

Effect of pulsed laser and laser-arc hybrid on aluminum/steel riveting-welding hybrid bonding technology

The microstructure and properties of aluminum (Al)-steel dissimilar metal riveting-welding joints obtained by the pulse laser and laser-arc hybrid welding methods were investigated. For simple laser beam riveting-welding Al and steel joint, the maximum tensile shear load of the joints was 6.3 kN, as the average laser beam power was about 438 W. The microstructure of the fusion zone (FZ) of the joint was twin martensite (TM), and there were small cracks in the weld. The Al elements were uniformly distributed in a vortex-shaped in the mixed region consisting of QP980 steel, 6061 Al alloy, and Q460 rivet, and the intermetallic compounds (IMCs) at the Al-steel interface had FeAl, Fe2Al5, and FeAl3. For the laser-arc hybrid riveting-welding joint, the maximum tensile shear load of the joint with an average laser power of 160 W and a tungsten inert gas (TIG) current 100 A was 7.25 kN. Lath martensite (LM), ferrite (F), and retained austenite (RA) were generated in the FZ of the joint, and the Al element aggregates in bulk and sporadically distributed in the mixed zone consisting of the steel plate, Al plate, and rivets. Furthermore, the differentiated distribution mechanism of Al element in riveting-welding hybrid joints was discussed in this paper.

LUE-200 Accelerator—A Photo-neutron Generator For The Pulsed Neutron Source “IREN”

This article reports about the construction and status of the accelerator facility at the Laboratory of Neutron Physics (FLNP) in the Joint Institute for Nuclear Research (JINR, Dubna), the driver of an intense pulsed resonance neutron source. The general scheme of the electron linear accelerator and features of its basic systems are presented. LUE-200 consists of two accelerating sections on a traveling wave with an operating frequency of 2856 MHz with RF power compression systems of the SLED type. The pulse current of the beam at the output of the accelerator reaches 2 A with a pulse duration of 80–100 ns. At the average energy of beam particles from 60–65 MeV and a cycle repetition rate of 50 Hz, the average beam power reaches ≈ 600 W. The integral neutron flux from the non-multiplying target reaches ∼ 1012 s−1.

Laser turning of alumina (Al2O3) ceramic by Nd:YAG laser technique

The present work focuses on the laser turning of Alumina (Al 2 O 3 ) ceramic materials and to analyze the effect of various machining input parameters. The design of experimental trials based on the Taguchi technique and the experimental process input values are considered such as pulse frequency, workpiece rotational speed, laser beam average power, and constant feed rate. The optimum process parametric settings are identified for the output parameters of surface roughness (R a ) and Material removal rate (MRR). The output responses are analyzed based on the signal-to-noise ratio. Based on the experimental study, the better surface roughness (R a ) is achieved as 2.37 µm for the input response combination of A 1 B 1 C 1 . Similarly, the Material removal rate is achieved as 0.79 mm 3 /min for the combination of A 1 B 1 C 3 .

First Protons in the ESS LINAC

The European Spallation Source (ESS), currently under construction in Lund, Sweden, will be the world’s brightest neutron source, driven by a linear accelerator (LINAC) with an average beam power of 5 MW at 2.0 GeV beam energy. The LINAC accelerates a proton beam of 62.5 mA peak current at 4% duty cycle (2.86 ms at 14 Hz). The accelerator uses a normal conducting front-end bringing the beam energy to 90 MeV, beyond that the acceleration up to 2 GeV is performed using superconducting structures. The first protons were extracted at the ESS site during the commissioning of the ion source and low energy beam transport that started earlier this year and will continue to the next stage of the commissioning up to 21 MeV early next year. This paper gives an overview of the status of the ESS accelerator and the commissioning of the ion source and the low energy beam transport.

Economical evaluation of radiation processing with high-intensity X-rays

Abstract X-rays application for radiation processing was introduced to the industrial practice, and in some circumstances is found to be more economically competitive, and offer more flexibility than gamma sources. Recent progress in high-power accelerators development gives opportunity to construct and apply reliable high-power electron beam to X-rays converters for the industrial application. The efficiency of the conversion process depends mainly on electron energy and atomic number of the target material, as it was determined in theoretical predictions and confirmed experimentally. However, the lower price of low-energy direct accelerators and their higher electrical efficiency may also have certain influence on process economy. There are number of auxiliary parameters that can effectively change the economical results of the process. The most important ones are as follows: average beam power level, spare part cost, and optimal shape of electron beam and electron beam utilization efficiency. All these parameters and related expenses may affect the unit cost of radiation facility operation and have a significant influence on X-ray process economy. The optimization of X-rays converter construction is also important, but it does not depend on the type of accelerator. The article discusses the economy of radiation processing with high-intensity of X-rays stream emitted by conversion of electron beams accelerated in direct accelerator (electron energy 2.5 MeV) and resonant accelerators (electron energy 5 MeV and 7.5 MeV). The evaluation and comparison of the costs of alternative technical solutions were included to estimate the unit cost of X-rays facility operation for average beam power 100 kW.

Mitigation of beam losses in LANSCE linear accelerator

The LANSCE accelerator has been in operation for nearly five decades. During this period, it was transformed from a 0.8 MW average proton beam power machine used primarily for the study of meson physics, to a multi-user high-power facility for fundamental research and national security applications, concurrently delivering beams to five distinct experimental areas. Minimization of beam losses in multi-beam application is a key issue for effective operation of accelerator facility. This paper summarizes recent experimental results in understanding and lowering of beam losses in LANSCE linear accelerator and high-energy beam transport lines.