Beam Intensity Research Articles

Nasopharyngeal carcinoma in a young adolescent with unilatral palatal palsy and neck mass – A rare case report

Nasopharyngeal carcinoma in a young adolescent with unilatral palatal palsy and neck mass – A rare case report

Highly focused beam generated with a height tuned micro-optical structure for high contrast microscopic imaging

Light sheet illumination technology improves the signal-to-noise ratio, resolution, and reduces scattered backgrounds for biological microscopic detection system. Here, we developed a novel micro-optical structure to produce a focused and uniform beam for the enhancement of imaging contrast. The beam intensity and working distance can be modified by adjusting the height and period of the structure. Our experiments successfully recorded structured light illumination, demonstrating the ability of the structure to capture high-contrast imaging data. We compared the light fields generated with and without the structure to assess the imaging quality, revealing a maximum 4.78-fold improvement in the signal-to-noise ratio. This work provides a potential method for high-resolution and high-contrast light sheet fluorescence microscopic detection.

Neutralized, intense-ion beams for fusion

A charge- and current-neutralized, intense-ion beam (IIB) will propagate undeflected in a magnetized plasma by the E×B , or diamagnetic, drift for a distance large compared to the beam-ion gyro-radius. This propagation occurs because of collective plasma effects when the beam-energy density is sufficient to sustain the polarization-electric field, or diamagnetic-screening currents. Our principal interest is the E×B drift, with β=Ebeam/Efield<1 . IIBs are characterized by parameters in the range: 0.1–2 MeV ion energy, 1–100 MA m−2 ion-current density, and 17–350 kW average power produced on repetitively-pulsed systems. Multi-MW average-beam power is possible with appropriate modifications to the power supply and ion-source/accelerator. IIBs can be focused geometrically, and/or magnetically, to spot sizes of the order of a few cm’s and their angular divergence is typically, ∼15 mRadians, suitable for long-range propagation in a vacuum beam-line. IIBs lose energy and momentum in the same manner as particles injected by a neutral-beam injector (NBIs), hence could be useful for fusion applications, including: heating, current drive, fueling, profile modifications, etc and such applications have yet to be thoroughly studied. Summarized here are the physical principles accounting for IIB propagation; ion-source designs used to produce the IIB; and pulsed-power methods for energizing the IIB accelerator. This technology base informs scalable metrics for the ion-source/accelerator (excluding the HV power supply and interconnects) used in a conceptual injector that provides the same ion energy and injected power (1 MeV, 17 MW) as NBIs used on ITER. A comparison indicates that the IIB injector would be much smaller in size, lower cost, and have much greater efficiency, while also providing for real-time modulation of the beam energy and intensity and the use of small-diameter injection ports that could minimize fuel contamination and magnetic-field leakage between the IIB injector and tokamak.

Twisted splitting and propagation factor of superimposed twisted Hermite-Gaussian Schell-model beams in turbulent atmosphere

We believe this to be a new superposition twisted Hermite-Gaussian Schell-model (STHGSM) beam hat is proposed. Analytic formulas for the intensity distribution and propagation factor of the STHGSM beam in non-Kolmogorov turbulence are derived by utilizing the generalized Huygens-Fresnel principle (HFP) and the Wigner function. The evolution characteristics of STHGSM beams propagating are numerically calculated and analyzed. Our findings indicate that the light intensity of the STHGSM beam gradually undergoes splitting and rotation around the axis during propagation through non-Kolmogorov turbulence, eventually evolving into a diagonal lobe shape at a certain distance of transmission. The anti-turbulence capability of the beam strengthens with higher beam order or twist factor values.

Analyzing the time-fractional (3 + 1)-dimensional nonlinear Schrödinger equation: a new Kudryashov approach and optical solutions

The paper focuses on investigating the time-fractional (3 + 1)-dimensional cubic and quantic nonlinear Schrödinger equation. We adopt the novel Kudryashov method to generate a distinct class of optical solutions for the current conformable fractional derivative problem. Our method explores various solution forms, including dark, wave, mixed dark-bright, and singular solutions. The soliton solutions we construct are visually represented to illustrate the influence of the fractional order derivative. Further, we elucidate the influence of solution parameters on the wave envelope, providing clear interpretations through 2D graphics presentations. The results underscore the efficacy of our approach in discovering exact solutions for nonlinear partial differential equations, especially in cases where alternative methods prove ineffective. The significance of the present paper lies in its contribution to advancing the understanding of the behavior of optical solutions in nonlinear systems, providing valuable insights for both theoretical and practical applications. In the field of nonlinear optics, this equation can describe the propagation of optical pulses in nonlinear media. It helps in understanding the behavior of intense laser beams as they propagate through materials exhibiting nonlinear optical effects such as self-focusing, self-phase modulation, and optical solitons.

Photonic hook propagation from eccentric microcylinder

The Photonic hook (PH) is an intricately curved photonic nanojet (PNJ) or a highly intense electromagnetic beam featuring a subwavelength waist, whose principal hallmark lies in its capacity to bend light at the nanoscale. According to existing literature, the origin of PH can be attributed to symmetry breaking, whereas symmetrical microstructures predominantly contribute to PNJ formation. This study presents the novel revelation of PH emergence from an isolated eccentric core–shell dielectric microcylinder, achieved through the illumination of a paraxial Gaussian beam (PGB). The eccentrically structured core–shell microscale geometry introduces an additional degree of freedom, influencing PH formation and directly shaping its characteristic parameters. Much like PNJ, the propagation of PH depends on different parameters such as core and shell refractive indices of the micro-structures, microstructure geometry, incident light type, and direction of propagation. A fascinating outcome from our numerical simulations is the switchable occurrence of PNJ and PH from an eccentric core–shell microcylinder by a simple adjustment of eccentricity, either parallel or perpendicular to the PGB’s propagation direction. This computational investigation emphasizes the impact of eccentricity and the incident wave’s beam waist, maintaining a consistent refractive index contrast between the core and shell. The outcomes are interpreted in terms of key parameters governing PH generation characteristics, encompassing FWHM, maximum electric field enhancement, and focal plane. Notably, we have observed the coexistence of whispering gallery modes (WGM) and PH within this system and these modes exhibit high sensitivity to the excitation wavelength. The potential applications of PH are believed to be far-reaching, including areas like optical trapping, sensing, and functioning as a versatile focusing element. This study contributes to the fundamental understanding of PH and illuminates its potential as a robust tool across diverse optical applications.

SPIRAL2 commissioning and operations

The SPIRAL2 linac is now successfully commissioned; H+, 4He2+, D+ and 18O6+ have been accelerated up to nominal parameters and 18O7+ and 40Ar14+ beams have been also accelerated up to 7 MeV/A. The main steps with 5 mA H+, D+ beams and with 0.6 mA 18O6+ are described. The general results of the commissioning of the RF, cryogenic and diagnostics systems, as well as the preliminary results of the first experiments on NFS are presented. In addition of an improvement of the matching to the linac, the tuning procedures of the 3 Medium Energy Beam Transport (MEBT) rebunchers and 26 linac SC cavities were progressively improved to reach the nominal parameters in operation, starting from the classical “signature matching method”. The different cavity tuning methods developed to take into account our particular situation (very low energy and large phase extension) are described. The tools developed for an efficient linac tuning in operation, e.g. beam energy and intensity changes are also discussed.

Influence of source parameters on the longitudinal phase-space distribution of a pulsed cryogenic beam of barium fluoride molecules

Recently, we have demonstrated a method to record the longitudinal phase-space distribution of a pulsed cryogenic buffer gas cooled beam of barium fluoride molecules with high resolution. In this paper, we use this method to determine the influence of various source parameters. Besides the expected dependence on temperature and pressure, the forward velocity of the molecules is strongly correlated with the time they exit the cell, revealing the dynamics of the gas inside the cell. Three observations are particularly noteworthy: (1) The velocity of the barium fluoride molecules increases rapidly as a function of time, reaches a maximum 50–200 µs after the ablation pulse and then decreases exponentially. We attribute this to the buffer gas being heated up by the plume of hot atoms released from the target by the ablation pulse and subsequently being cooled down via conduction to the cell walls. (2) The time constant associated with the exponentially decreasing temperature increases when the source is used for a longer period of time, which we attribute to the formation of a layer of isolating dust on the walls of the cell. By thoroughly cleaning the cell, the time constant is reset to its initial value. (3) The velocity of the molecules at the trailing end of the molecular pulse depends on the length of the cell. For short cells, the velocity is significantly higher than expected from the sudden freeze model. We attribute this to the target remaining warm over the duration of the molecular pulse giving rise to a temperature gradient within the cell. Our observations will help to optimize the source parameters for producing the most intense molecular beam at the target velocity.

Analytical modeling of the spray amplification of a spatially smoothed laser beam

Spatial amplification of the near-forward Brillouin scattering (FSBS) produced by a laser beam smoothed with a random phase plate (RPP) is considered by using a novel technique based on the central limit theorem [C. Ruyer et al., Phys. Rev. E 107, 035208 (2023)]. It is demonstrated that FSBS amplification proceeds over a length much larger than the longitudinal speckle correlation length and, under certain conditions, scales as a square of the average gain coefficient. Analytical expressions for the spatial gain are successfully compared with paraxial electromagnetic simulations, demonstrating that the beamlet correlation through ion-acoustic waves dominates the spatial growth for intense enough laser beams. The scattered wave aperture increases with the gain and can extend beyond the small angle scattering limit. These results open the way for developing reduced modeling of beam spray amplification in radiation hydrodynamics codes.

Dual-mode rectangular microwave cavity for precision spectroscopy of hyperfine structure in muonium

Precision microwave spectroscopy of the ground-state hyperfine structure in muonium provides a stringent test of the Standard Model in particle physics. The MuSEUM collaboration is preparing for such a measurement, aiming for precision down to ≈1ppb, utilizing the world’s most intense pulsed muon beam at J-PARC. The measurement of the Zeeman-split structure with an external magnetic field of 1.7T also precisely determines the muon’s magnetic moment (≈10ppb). In the future, improved precision of the magnetic moment can be potentially obtained by measurements with different magnetic field strengths, however, it entails upgrading current cylindrical microwave cavities to rectangular ones. As the first step for the upgrade, we have developed a dual-mode rectangular cavity for the measurement with 2.9T field. The electromagnetic design and production have been established, and frequency sweeping with two desired modes has been successfully demonstrated. Moreover, the overall performance of the measurement at 2.9T field was evaluated with Monte Carlo simulations. These studies pave the way for a further extension of the MuSEUM experiment at various strengths of the magnetic fields.

Intensity-modulated therapy for breast cancer patients. Practical guidelines and tips for an effective treatment planning strategy.

PurposePractical guidelines and tips for effective and robust radiotherapy treatment planning for breast cancer patients are addressed for intensity-modulated fixed field or volumetric modulated arc therapy techniques. The concepts described here are general and valid on all the treatment planning systems. However, some details have been shown here applied to the Varian platforms used at the authors’ institutions. MethodsThe specific aspects of using C-arm or O-ring mounted linear accelerators are covered in the document, as well as tips for dealing with certain resource constraints, target cropping and skin flash aiming to reduce risks of skin toxicity and to manage (residual after breath control) respiration motion or oedema. ResultsA decision tree is presented, and practical solutions are discussed for cases where a target volume is contoured or not; where volumetric modulated arc therapy or fixed beams intensity modulation should be applied and details about the technical implementation (tangential IMRT, butterfly IMRT or VMAT, large partial VMAT arcs). Target cropping and skin flash implications are discussed in detail, and links to plan robustness are outlined. ConclusionsPractical guidelines for breast planning are presented and summarized with a decision tree and technical summaries.

Validation of the diamond detectors for the Super Fragment Separator beam diagnostics

The Super-FRS at the FAIR accelerator complex will adopt Chemical Vapor Deposition diamond detectors as radiation-hard particle rate counters. Their role will be to monitor the beam transmission for beams with ions rates up to 107 ions/spill and to calibrate the other beam diagnostics devices that are in duty at higher beam intensities. The target vacuum chamber of the Super-FRS hosts a 7 × 7 mm2 single crystal diamond and a 25 × 25 mm2 polycrystalline diamond: they are required to detect crossing particles with high efficiency (> 98%) in the case of heavy ion species (Ar to U), and to stand for several years in an environment in which they can potentially accumulate a dose of a few MGy per year. Laboratory measurements and beam test campaigns were arranged in the past years for the validation of the proposed sensors, in particular for the case of the polycrystalline technology. Here we report the outcome of the irradiation of a sensor based on a 20 × 20 mm2 polycrystalline diamond produced by Element Six, with high intensity 1 GeV/nucleon Pb and U beams at GSI (Darmstadt). The detector signal shape characteristics and the ion counting efficiency have been monitored by interleaving periods of low ions rates, to evaluate possible damages or performance degradation during and after a total bombardment of about 6 × 1011 heavy ions.

Thermal Stability and Non-Linear Optical and Dielectric Properties of Lead-Free K0.5Bi0.5TiO3 Ceramics.

Lead-free K0.5Bi0.5TiO3 (KBT) ceramics with high density (~5.36 g/cm3, 90% of X-ray density) and compositional purity (up to 90%) were synthesized using a solid-state reaction method. Strongly condensed KBT ceramics revealed homogenous local microstructures. TG/DSC (Thermogravimetry-differential scanning calorimetry) techniques characterized the thermal and structural stability of KBT. High mass stability (>0.4%) has proven no KBT thermal decomposition or other phase precipitation up to 1000 °C except for the co-existing K2Ti6O13 impurity. A strong influence of crystallites size and sintering conditions on improved dielectric and non-linear optical properties was reported. A significant increase (more than twice) in dielectric permittivity (εR), substantial for potential applications, was found in the KBT-24h specimen with extensive milling time. Moreover, it was observed that the second harmonic generation (λSHG = 532 nm) was activated at remarkably low fundamental beam intensity. Finally, spectroscopic experiments (Fourier transform Raman and far-infrared spectroscopy (FT-IR)) were supported by DFT (Density functional theory) calculations with a 2 × 2 × 2 supercell (P42mc symmetry and C4v point group). Moreover, the energy band gap was calculated (Eg = 2.46 eV), and a strong hybridization of the O-2p and Ti-3d orbitals at Eg explained the nature of band-gap transition (Γ → Γ).

Measuring non-linear Faraday rotation in cold atoms in presence of persistent transverse fields using tunable differential imaging

Non-linear Faraday rotation in cold atoms promises precision magnetometry due to narrower magnetic resonance linewidth compared to the linear Faraday effect. Imaging techniques based on linear Faraday effect have emerged as a tool to characterize the dynamics of ultracold atomic clouds. Using a camera instead of balanced detectors, we can obtain the spatial distribution of polarization rotation in a uniformly intense optical beam. However, the finite dynamic range of the imaging device limits the sensitivity to measure non-linear Faraday rotation at a given incident power. Here, we experimentally demonstrate a differential imaging technique in which we can tune parameters to improve contrast and the sensitivity to the non-linear Faraday rotation signal by a factor of ≈7 over existing imaging methods. The atomic cloud experiences a uniform optical field even when shifted by persistent magnetic fields making the method robust. This allows us to study the effect of transverse fields on non-linear Faraday rotation in ultra-cold atoms, paving the way toward spatially resolved vector magnetometry.

Dynamics of induced optical torque via optical vortex light

This paper investigates the dynamics of induced torque in Nitrogen-Vacancy (NV) centers interacting with two weak optical vortex beams as well as a strong control field, exploring the impact of different system parameters such as control field intensity, detuning, magnetic field, and vortex beam strength. We find a dispersive torque behavior, indicating the sensitivity of NV centers to control parameters. Magnetic field induces level splitting, leading to a transformative effect on torque, with notable enhancements observed at specific intensities. Additionally, non-resonant torque is explored, demonstrating the controllability of torque peaks through magnetic field manipulation. Unequal strengths of vortex beams is found to yield substantial enhancements in torque. These results provide crucial insights into the induced torque dynamics in NV centers, presenting opportunities for optimized torque-based applications in quantum systems.

Effect of mutual interaction of two cosh-Gaussian laser beams on upper hybrid wave excitation and subsequent electron acceleration

This paper presents the excitation of an upper hybrid wave by resonant excitation of two intense cosh-Gaussian laser beams of frequencies ω 1 and ω 2 in a collisionless plasma. The excited upper hybrid wave is used for electron acceleration which accelerates the electrons towards higher energy. The acceleration of electrons through an excited upper hybrid wave has also been studied. This study has been analysed using the Wentzel Kramers Brillouin (WKB) and paraxial-ray approximation, where relativistic and ponderomotive nonlinearities are employed together. Analytical expressions for the beam width/intensity of the cosh-Gaussian laser beams, the electric field/power of the excited upper hybrid wave and the electron acceleration have been derived, which have been solved numerically for an established set of laser and plasma parameters. The results are also compared to relativistic nonlinearity. It has been observed that the mutual interaction of two cosh-Gaussian laser beams at a difference frequency significantly affects the self-focusing of each beam, leading to an increase in the amplitude/power of the upper hybrid wave as well as energy gain by the electrons. The effect of the magnetic field (ωc) and decentered parameter (b) on the power of the excited upper hybrid wave and the energy gain by the electrons are also explored. The results show that the power of upper hybrid wave and the energy gain by the electrons increase at higher values ​​of b and ω c.

Beamline design for multipurpose muon beams at CSNS EMuS

A new muon beam facility, called the Experimental Muon Source (EMuS), was proposed for construction at the China Spallation Neutron Source (CSNS). The design of the complex muon beamlines for the EMuS baseline scheme, which is based on superconducting solenoids, superferric dipoles and room-temperature magnets, is presented herein. Various muon beams, including surface muons, decay muons and low energy muons, have been developed for multipurpose applications. The optics design and simulation results of the trunk beamline and branch beamlines are presented. With a proton beam power of 25 kW at a standalone target station that consists of a conical graphite target and high-field superconducting solenoids, the muon beam intensity in the trunk beamline varies from 107/s for surface muons to 1010/s for high-momentum decay muons. And at the endstations, these values vary from 105/s for surface muons to 108/s for decay muons.

A comparative study on the axial intensity of some laser beams spreading through human and mouse biological tissues

A comparative study on the axial intensity of some laser beams spreading through human and mouse biological tissues

Fractal Growth of 2D NbSe2 for Broadband Nonlinear Optical Limiting

AbstractThe compelling demand for laser protection both for civil and defense use calls for new‐generation nonlinear optical materials. Chemical vapor deposition (CVD) techniques provide extra tricks to modulate crystal optical nonlinearity through fractal growth. The synthesized 2D NbSe2 and its fractal structures exhibit giant, broadband laser attenuation behaviors extending into the near Infrared (NIR) range. Particularly, the optical limiting performance generally correlates with the fractal dimension, where Fractal NbSe2 demonstrates enhanced third‐order optical nonlinearity at a huge nonlinear absorption coefficient of 9.7 × 10−4 m W−1 and an ultralow starting threshold of 5 mJ cm−2 at 532 nm. Various techniques include femtosecond spectroscopy, Density functional theory (DFT) calculation and Kelvin probe force microscopy disclose the origin of the strong nonlinearity of the 2D NbSe2 crystals, and suggest the formation of edge states and overall faster carrier dynamics, larger surface contact potential difference NbSe2 fractals contribute to their even augmented nonlinear responses. Fractal engineering thus opens new avenues to fabricate highly efficient laser protection materials, and the blocking of intense beam (a large attenuation factor over 13.3 dB at 532 nm) while allowing transmission of weak one (a high linear optical transmittance over 80%) fulfills the much desired “smart” defense.

A metasurface-based full-color circular auto-focusing Airy beam transmitter for stable high-speed underwater wireless optical communications

Due to its unique intensity distribution, self-acceleration, and beam self-healing properties, Airy beam holds great potential for optical wireless communications in challenging channels, such as underwater environments. As a vital part of 6G wireless network, the Internet of Underwater Things requires high-stability, low-latency, and high-capacity underwater wireless optical communication (UWOC). Currently, the primary challenge of UWOC lies in the prevalent time-varying and complex channel characteristics. Conventional blue Gaussian beam-based systems face difficulties in underwater randomly perturbed links. In this work, we report a full-color circular auto-focusing Airy beams metasurface transmitter for reliable, large-capacity and long-distance UWOC links. The metasurface is designed to exhibits high polarization conversion efficiency over a wide band (440-640 nm), enabling an increased data transmission rate of 91% and reliable 4 K video transmission in wavelength division multiplexing (WDM) based UWOC data link. The successful application of this metasurface in challenging UWOC links establishes a foundation for underwater interconnection scenarios in 6G communication.