Beam Intensity Research Articles

ASTERICS, a new 28 GHz electron cyclotron resonance ion source for the SPIRAL2 accelerator

A new A/Q=7 injector is under development for the SPIRAL2 accelerator at Caen, France (NEWGAIN project). A new 28 GHz superconducting electron cyclotron resonance ion source named ASTERICS is under design for this project. The source features a modern cryostat and a large plasma chamber (91 mm radius and 600 mm length). The physical and technical motivations for a larger plasma volume are detailed and estimates of expected beam intensities enhancement are discussed. The source will mainly produce metallic ion beams: the concept of a temperature-controlled liner (up to 900°C) to stabilize high vapor pressure metal re-evaporation in the source is presented. The preliminary design of the ion source and its superconducting magnet are described.

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.

Design for an 18 GHz Open Hexapole Electron Cyclotron Resonance Ion Source

Responding to a request by the user community for higher beam intensities, an upgrade of the Argonne National Laboratory ECR2 ion source is in progress. The upgrade has three main constraints: 1) The overall source architecture as defined by the solenoid coils cannot change, 2) radial access to the plasma chamber has to be maintained, and 3) the amount of time the source can be shut down for hardware installation is < 2 months. A new NdFeB open hexapole is projected to produce a 1.19 T wall field (r = 38.1 mm) with six radial slots (6.35 mm x 91.2 mm) allowing solid material access and ∼120 l/s of pumping to the plasma chamber. The axial magnetic fields will be enhanced with a vanadium permendur plug and optimization of the iron resulting in a magnetic field at injection Binj of 2.4 T, magnetic field at center Bmin of 0.4 T, and magnetic field at extraction Bext of 1.0 T and magnetic gradients Bgrad of 5.9 T/m for 14.5 GHz and 7.4 T/m for 18 GHz. The plasma is currently heated with multiple-frequency RF provided by two traveling wave tube amplifiers (TWTA) operating between 11 and 14.5 GHz and capable of providing 1100 W total power. The new magnetic structure will support 18 GHz operation with RF provided by a new TWTA.

Simulation of laser-plasma focusing using taper solenoid

A laser ion source can produce ion beams of various elements, including high melting point metals. Owing to its ability to switch beams rapidly by loading multiple solid targets, we are developing a laser ion source to implement it in a 400 kV ion implanter, which requires a wide range of ion species. Although a laser ion source offers above advantages, most of the plasma is lost in an ion source due to the generation of the beam from a part of the diffused plasma with a broad angular distribution. To suppress this loss and enhance beam intensity, we employ a linear solenoid to increase the amount of plasma reaching the extraction electrode by suppressing the three-dimensional plasma diffusion. However, the linear solenoid cannot suppress the loss of plasma near the target as the plasma spreads three-dimensionally from the plasma generation point. Therefore, by placing a taper solenoid near the target, it is possible to suppress the diffusion of plasma immediately after its generation and to transport most of the generated plasma to the extraction electrode. In this paper, we present the results of plasma trajectory calculations using the particle-in-cell method by the plasma simulations involving taper solenoids.

Absorption characteristics of diffracted X-ray radiation in a quartz crystal at an external temperature gradient

In this work the dependence of the anomalous absorption of X-rays on the crystal thickness and temperature gradient value was studied. The refracted and reflected beams intensities, as well as their sum intensities were measured for crystal thicknesses in the range of 0.3–4.5 mm. Significant increase in the sum intensity of the refracted and reflected beams is observed in presence of temperature gradient. It is shown that the anomalous absorption in the crystal in presence of the temperature gradient is decreased and this effect is stronger expressed in thick crystals.

Intense vanadium ion beam production for super-heavy element research experiments

Long-term production of an intense 51V13+ ion beam was imperative for synthesizing a new element (Z=119) at RIKEN. We systematically measured the beam intensity as a function of microwave power and material consumption rate for effectively producing an intense beam. Consequently, we generated a 1 emA of 51V13+ ion beam at an injected microwave power and extraction voltage of 3.5 kW and 12.6 kV, respectively.

High intensity beam dynamics assessment and challenges for HL-LHC

The High Luminosity (HL-LHC) project aims to increase the integrated luminosity of CERN's Large Hadron Collider (LHC) by an order of magnitude compared to its initial design. This requires a large increase in bunch intensity and beam brightness compared to the first three LHC runs, and hence poses serious collective-effects challenges, related in particular to electron cloud, instabilities from beam-coupling impedance, and beam-beam effects. Here, we present the associated constraints and the mitigation measures proposed to achieve the baseline performance of the upgraded LHC machine. We also discuss the interplay of these mitigation measures with other aspects of the accelerator, such as optics, physical and dynamic apertures, the collimation system, and crab cavities. Additional potential sources of intensity limitations are also briefly discussed.

A compact start time counter using plastic scintillators readout with MPPC arrays for the WASA-FRS HypHI experiment

We have developed a compact detector for measuring beam particles using plastic scintillators readout through Multi-Pixel Photon Counters, which is employed for hypernuclear measurements in the WASA-FRS experiment at GSI. The Time-of-Flight resolution of the newly-developed detector has been investigated in relation to the overvoltage with respect to the breakdown voltage, a maximum counting rate of approximately 3×106/s per segment, and a maximum beam charge of Z = 6. The evaluated Time-of-Flight resolutions between the neighboring segments of the detector range from 44.6±1.3 ps to 100.3±3.6 ps (σ) depending on the segment, overvoltage values, and beam intensity. It is also observed that the Time-of-Flight resolution is inversely correlated to the beam atomic charge (Z).

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.

Thickness-dependent neutron detection efficiency of LiF-Si-based active neutron detector for boron neutron capture therapy

A LiF-Si-based active neutron detector was developed for the measurement of real-time BNCT neutron beam. Thermal-neutron detection efficiencies were adjustable to the neutron beam intensities at various measurement locations by simply exchanging the LiF neutron converter, while minimizing sensitivity to photons. The neutron detection efficiency ranges from 8 × 10−7 to 8 × 10−4 cm2. The thermal-neutron detection efficiencies were experimentally obtained by placing the neutron detectors inside an education reactor. Experimental results were verified using a Monte Carlo simulation technique. The simulated thermal-neutron detection efficiencies were in good agreement with the experimental results within the range of experimental uncertainties. Discrepancies in both sets of results were due to an insufficient assessment of LiF density and flatness. Surface-density neutron detection efficiencies were proposed to more accurately measure neutron fluence rates.

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.

Development of compact-modulated absorption/emission technique towards micro-gravity sooting flame measurements

To meet the experimental physical limitations on Chinese Space Station (CSS), three compact-modulated absorption/emission (CMAE) implementations are miniaturized progressively from original MAE layout, which are investigated as potential options for simultaneous soot temperature and volume fraction measurements in the axis-symmetric flames. Contrasted with the original MAE technique, a white LED point light source (diameter of ϕ = 8 mm) and a white LED planar light source (rectangle of 200 × 120 mm2) in turns replaces the laser source, by which the light beam homogeneous implementation is significantly simplified. Moreover, a 3-CMOS prism-based camera enables simultaneously recording flame two color radiations that reduces the detecting complexity. It is found that backlight beam intensity should be more than 2.5 times the flame radiation intensity to avoid abnormal extinction coefficient on the flame edge in this configuration. Moreover, the robustness and consistency of the three CMAEs measurements are validated with a standard Santoro’s flame, and low average standard deviation ranges of ±0.04∼±0.06 ppm and ±65.0∼± 96.3 K for soot volume fraction and temperature respectively is evaluated from error propagation assessment. As such, the proposed CMAE-2 and CMAE-3 layouts are promising candidates for high-fidelity flame soot parameters measurements under limited space, weight and power supply on CSS.

Stability of titanium deuteride films irradiated with pulsed ion beams

Titanium deuteride films are widely used as target materials for neutron generators. Intense pulsed ion beams irradiated titanium deuteride films, and their structure stabilities were investigated by combination with scanning electron microscopy, transmission electron microscopy, grazing incidence angle X-ray diffraction, slow positron beam, scratch test and finite element analysis. The beam energy density was 0.3 J/cm2. Five different irradiation fluences of 3 × 1014, 1 × 1015, 3 × 1015, 1 × 1016, 3 × 1016 cm−2 were performed at room temperature. The adhesion strength between the film and Mo substrate decreased with increasing fluence. Moreover, surface melting and grain growth occurred after the beam irradiation with fluences over 3 × 1015 cm−2. The morphology of scratch tracks shows that the titanium deuteride film suffers a transition from ductile fracture to brittle fracture with increasing fluence. The reason for the decreasing adhesion strength was discussed via the introduction of thermal stress and lattice structure recovery. The research result is critical for evaluating the lifetime of titanium deuteride films based on failures in structures and a decrease in concentration of the inner deuterium.

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.

Vehicle Headlight Automatic Bright and Dim Control System

Headlights of vehicles pose a great danger during night driving. The drivers of most vehicles use high, bright beam while driving at night. This causes a discomfort to the person travelling from the opposite direction and therefore experiences a sudden glare for a short period of time. This is caused due to the high intense headlight beam from the other vehicle coming towards the one from the opposite direction. In this paper, an automatic headlight dimmer which uses a sensor has been designed to dim the headlight of on-coming vehicles to avoid human eye effects. This automatically switched the high beam into low beam, therefore reducing the glare effect by sensing the light intensity value of approaching vehicle. Road accidents are a serious cause of concern and glare from headlamps of vehicles during night time create havoc for the drivers making driving really an uphill task and due to the undesirable situation, drivers meet with accidents. It’s a very hectic job for the drivers to manually control the beam of the headlamps during night from time to time when an oncoming vehicle is located within 150 meters of the other vehicle. So, it’s high time when a safety control unit should be installed in vehicles that can automatically dim the headlamps by detecting their intensity which, otherwise, might cause a serious trouble for the drivers. Our work proposes a cost effective and useful control unit which will automatically detect the excessive glare from headlamps and will give a signal to the oncoming vehicle causing the trouble to dim the lamps. As such, the driver’s unnecessary load will be reduced and driving will become safer and smoother during night.