Search Results (60)

Our work presents a laser fuze detector structure with a four-channel center-symmetrical emitting laser under the influence of the three-dimensional (3D) and spatial properties of smoke clouds, which was used to improve the laser fuze’s anti-smoke interference ability, as well as the target detection performance. A laser echo signal model under multiple frequency-modulated continuous-wave (FMCW) lasers was constructed by investigating the hybrid collision scattering process of photons and smoke particles. Using a virtual particle system implemented in Unity3D, the laser target characteristics were studied under the conditions of multiple smoke particle characteristic variations. The simulation results showed that false alarms in low-visibility and missed alarms in high-visibility smoke scenes could be effectively solved with four emitting lasers. With this structure of the laser fuze prototype, the smoke echo signal and the target echo signal could be separated, and the average amplitude growth rate of the target echo signal was improved. The conclusions are supported by the results of experiments. Therefore, this study not only reveals laser target properties for 3D and spatial properties of particles, but also provides design guidance and reasonable optimization of FMCW laser fuze multi-channel emission structures in combination with multi-particle collision types and target characteristics. Full article

Belle II is a particle physics experiment working at an high luminosity collider within a hard irradiation environment. The Time-Of-Propagation detector, aimed at the charged particle identification, surrounds the Belle II tracking detector on the barrel part. This detector is composed by 16 modules, each module contains a finely fused silica bar, coupled to microchannel plate photomultiplier tube (MCP-PMT) photo-detectors and readout by high-speed electronics. The MCP-PMT lifetime at the nominal collider luminosity is about one year, this is due to the high photon background degrading the quantum efficiency of the photocathode. An alternative to these MCP-PMTs is multi-pixel photon counters (MPPC), known as silicon photomultipliers (SiPM). The SiPMs, in comparison to MCP-PMTs, have a lower cost, higher photon detection efficiency and are unaffected by the presence of a magnetic field, but also have a higher dark count rate that rapidly increases with the integrated neutron flux. The dark count rate can be mitigated by annealing the damaged devices and/or operating them at low temperatures. We tested SiPMs, with different dimensions and pixel sizes from different producers, to study their time resolution (the main constraint that has to satisfy the photon detector) and to understand their behavior and tolerance to radiation. For these studies we irradiated the devices to radiation up to $5\times {10}^{11}1$ MeV neutrons equivalent (neq) per cm² fluences; we also started studying the effect of annealing on dark count rates. We performed several measurements on these devices, on top of the dark count rate, at different conditions in terms of overvoltage and temperatures. These measurements are: IV-curves, amplitude spectra, time resolution. For the last two measurements we illuminated the devices with a picosecond pulsed laser at very low intensities (with a number of detected photons up to about twenty). We present results mainly on two types of SiPMs. A new SiPM prototype developed in collaboration with FBK with the aim of improving radiation hardness, is expected to be delivered in September 2025. Full article

Today, Powder Bed Fusion-Laser Based technology is widely used in many industrial fields, but some high-demanding applications are still not fully investigated, such as low temperatures. In basic physics research, experiments usually use low temperatures to reduce external influences and to increase the sensitivity of particle detectors, accelerators, etc. The production capabilities of this technology have become a standard for manufacturing such components, and the demand for high performance has led to the investigation of new materials, like GRCop-42. It possesses excellent thermal properties and strength at high temperatures, and although several works have been published in recent years, full research on its behaviour at low temperatures is still missing. The aim of the paper is to investigate the mechanical properties of GRCop-42, produced by PBF-LB, from low to room temperature, like Elastic Modulus and Poisson’s ratio, and correlate them with thermal conductivity in the as-built state and after heat treatment. The results showed that the material can maintain high strength even at low temperatures, without losing ductility and the ability to store strain energy; moreover, after heat treatment, it increases its thermal properties due to the way the precipitates are dispersed in the copper matrix. Full article

Timing measurements are critical for the detectors at the future HL-LHC, to resolve reconstruction ambiguity when the number of simultaneous interactions reaches up to 200 per bunch crossing. The ATLAS collaboration therefore builds a new High-Granularity Timing detector for the forward region. A customized ASIC, called ALTIROC, has been developed, to read out fast signals from low-gain avalanche detectors (LGADs), which has 50 ps time-resolution for signals from minimum-ionizing particles. To meet these requirements, a custom-designed pre-amplifier, a discriminator, and TDC circuits with minimal jitter have been implemented in a series of prototype ASICs. The latest version, ALTIROC3, is designed to contain full functionality. Hybrid assemblies with ALTIROC3 ASICs and LGAD sensors have been characterized with charged-particle beams at CERN-SPS and with laser-light injection. The time-jitter contributions of the sensor, pre-amplifier, discriminator, TDC, and digital readout are evaluated. Full article

The development of advanced detection systems for charged particles in laser-based accelerators and the need for precise time of flight measurements have led to the creation of detectors using ultra-thin plastic scintillators, indicating their use as transmission detectors with low energy loss and minimal dispersion for protons around a few MeV. This study introduces a new detection system designed by the Institute for Instrumentation in Molecular Imaging for time of flight and timing applications at the National Accelerator Center in Seville. The system includes an ultra-thin EJ-214 plastic scintillator coupled with a photomultiplier tube and shielded by aluminized mylar sheets. The prototype installation as an external trigger system at the ion beam nuclear microprobe of the aforementioned facility, along with its temporal performance and ion transmission, was thoroughly characterized. Additionally, the scintillator thickness and uniformity were analyzed using Rutherford backscattering spectrometry. Results showed that the experimental thickness of the EJ-214 sheet differs by approximately 46% from the supplier specifications. The detector response to MeV protons demonstrates a strong dependence on the impact position but remains mostly linear with the applied working bias. Finally, single ion detection was successfully achieved, demonstrating the applicability of this new system as a diagnostic tool. Full article

We demonstrate a method to characterize the beam energy, transverse profile, charge, and dose of a pulsed electron beam generated by a 1 kHz TW laser-plasma accelerator. The method is based on imaging with a scintillating screen in an inhomogeneous, orthogonal magnetic field produced by a wide-gap magnetic dipole. Numerical simulations were developed to reconstruct the electron beam parameters accurately. The method has been experimentally verified and calibrated using a medical LINAC. The energy measurement accuracy in the 6–20 MeV range is proven to be better than 10%. The radiation dose has been calibrated by a water-equivalent phantom, RW3, showing a linear response of the method within 2% in the 0.05–0.5 mGy/pulse range. Full article

A new scintillation material composed of InAs quantum dots (QDs) hosted within a GaAs matrix was developed, and its performance with different types of radiation is evaluated. A methodology for designing an integrated photodetector (PD) with a low defect density and that is optically matched to the QD’s emission spectrum is introduced, utilizing an engineered epitaxial InAlGaAs metamorphic buffer layer. The photoluminescence (PL) collection efficiency of the integrated PD is examined using two-dimensional scanning laser excitation. The detector response to 5.5 MeV α-particles and 122 keV photons is presented. Yields of 13 electrons/keV for α-particles and 30–60 electrons/keV for photons were observed. The energy resolution of 12% observed with α-particles was mainly limited by noise- and geometry-related optical losses. The radiation hardness of an InAs QDs hosted within GaAs and a wider band gap AlGaAs ternary alloy was studied under a 1 MeV proton implantation up to a 10¹⁴ cm⁻² dose. The integrated PL responses were compared to evaluate PL quenching due to non-radiative defects. The QDs embedded in the AlGaAs demonstrated improved radiation hardness compared to QDs in the GaAs matrix and in the InGaAs quantum wells. Full article

Highly intense bunches of protons and ions with energies of several MeV/u can be generated with ultra-short laser pulses focused on solid targets. In the most common interaction regime, target normal sheath acceleration, the spectra of these particles are spread over a wide range following a Maxwellian distribution. We report on the design and testing of a magnetic chicane for the selection of protons within a limited energy window. This consisted of two successive, anti-parallel dipole fields generated by cost-effective permanent C-magnets with customized configuration and longitudinal positions. The chicane was implemented into the target vessel of a petawatt laser facility with constraints on the direction of the incoming laser beam and guidance of the outgoing particles through a vacuum port. The separation of protons and carbon ions within distinct energy intervals was demonstrated and compared to a ray tracing code. Measurements with radiochromic film stacks indicated the selection of protons within [2.4, 6.9] MeV, [5.0, 8.4] MeV, or ≥6.9 MeV depending on the lateral dispersion. A narrow peak at 4.8 MeV was observed with a time-of-flight detector. Full article

We propose novel spectrometer designs that aim to enhance the measured spectral range of ions on a finite-sized detector. In contrast to the traditional devices that use a uniform magnetic field, in which the deflection of particles increases inversely proportional to their momentum, in a gradient magnetic field, the deflection of particles will decrease due to the reduction of the magnetic field along their propagation. In this way, low-energy ions can reach the detector because they are deflected less, compared to the uniform field case. By utilizing a gradient magnetic field, the non-linear dispersion of ions in a homogeneous magnetic field approaches nearly linear dispersion behavior. Nonetheless, the dispersion of low-energy ions, using a dipole field, remains unnecessarily high. In this article, we discuss the employed methodology and present simulation results of the spectrometer with an extended ion spectral range, focusing on the minimum detectable energy (energy dynamic range) and energy resolution. Full article

LIDAR is central to the perception systems of autonomous vehicles, but its performance is sensitive to adverse weather. An object detector trained by deep learning with the LIDAR point clouds in clear weather is not able to achieve satisfactory accuracy in adverse weather. Considering the fact that collecting LIDAR data in adverse weather like dusty storms is a formidable task, we propose a novel data augmentation framework based on physical simulation. Our model takes into account finite laser pulse width and beam divergence. The discrete dusty particles are distributed randomly in the surrounding of LIDAR sensors. The attenuation effects of scatters are represented implicitly with extinction coefficients. The coincidentally returned echoes from multiple particles are evaluated by explicitly superimposing their power reflected from each particle. Based on the above model, the position and intensity of real point clouds collected from dusty weather can be modified. Numerical experiments are provided to demonstrate the effectiveness of the method. Full article

The shortage of ${}^3$He, a crucial element widely used as a neutron converter in neutron detection applications, has sparked significant research efforts aimed at finding alternative materials, developing appropriate deposition methods, and exploring new detector architectures. This issue has required the exploration of novel approaches to address the challenges faced in neutron detection. Among the available conversion materials, ${}^{10}$B has emerged as one of the most promising choices due to its high neutron-capture cross-section and relatively high Q value. In our previous papers, we delved into the possibility of depositing neutron conversion layers based on ${}^{10}$B using Pulsed Laser Deposition (PLD). We investigated and evaluated the performance of these layers based on various factors, including deposition conditions, substrate properties, and film thickness. Moreover, we successfully developed and tested a device that employed a single conversion layer coupled with a silicon particle detector. In this current study, we present the development of a new device that showcases improved performance in terms of efficiency, sensitivity, and discrimination against $\gamma$ background signals. The background signals can arise from the environment or be associated with the neutron field. To achieve these advancements, we considered a new detection geometry that incorporates the simultaneous use of two ${}^{10}$B conversion layers, each with a thickness of 1.5 $\mathsf{\mu }$m, along with two solid-state silicon detectors. The primary objective of this design was to enhance the overall detection efficiency when compared to the single-layer geometry. By employing this novel setup, our results demonstrate a significant enhancement in the device’s performance when exposed to a neutron flux from an Am-Be neutron source, emitting a flux of approximately 2.2 × 10${}^6$ neutrons per second. Furthermore, we established a noteworthy agreement between the experimental data obtained and the simulation results. Full article

X-ray production through betatron radiation emission from electron bunches is a valuable resource for several research fields. The EuAPS (EuPRAXIA Advanced Photon Sources) project, within the framework of EuPRAXIA, aims to provide 1–10 keV photons (X-rays), developing a compact plasma-based system designed to exploit self-injection processes that occur in the highly nonlinear laser-plasma interaction (LWFA) to drive electron betatron oscillations. Since the emitted radiation spectrum, intensity, angular divergence, and possible coherence strongly depend on the properties of the self-injected beam, accurate preliminary simulations of the process are necessary to evaluate the optimal diagnostic device specifications and to provide an initial estimate of the source’s performance. A dedicated tool for these tasks has been developed; electron trajectories from particle-in-cell (PIC) simulations are currently undergoing numerical analysis through the calculation of retarded fields and spectra for various plasma and laser parameter combinations. The implemented forward approach evaluation of the fields could allow for the integration of the presented scheme into already existing PIC codes. The spectrum calculation is thus performed in detector time, giving a linear complex exponential phase; this feature allows for a semi-analitical Fourier transform evaluation. The code structure and some trajectories analysis results are presented. Full article

Charged particle beams driven to ultra-high dose rates (UHDRs) have been shown to offer potential benefits for future clinical applications, particularly in the reduction of normal-tissue toxicity. Studies of the so-called FLASH effect have shown promise, generating huge interest in high dose rate radiation studies. With laser-driven proton beams, where the duration of the proton burst delivered to a sample can be as short as hundreds of picoseconds, the instantaneous dose rates are several orders of magnitude higher than those used for conventional radiotherapy. The dosimetry of these beam modalities is not trivial, with conventional active detectors, such as ionisation chambers, experiencing saturation effects making them unusable at the extremely high dose rates. Calorimeters, measuring the radiation-induced temperature rise in an absorber, offer an ideal candidate for the dosimetry of UHDR beams. However, their application in the measurement of laser-driven UHDR beams has so far not been trialled, and their effective suitability to work with the quasi-instantaneous and inhomogeneous dose deposition patterns and the harsh environment of a laser-plasma experiment has not been tested. The measurement of the absorbed dose of laser-driven proton beams was conducted in a first-of-its-kind investigation, employing the VULCAN-PW laser system of the Central Laser Facility (CLF) at the Rutherford Appleton Laboratory (RAL), using a small-body portable graphite calorimeter (SPGC) developed at the National Physical Laboratory (NPL) and radiochromic films. A small number of shots were recorded, with the corresponding absorbed dose measurements resulting from the induced temperature rise. The effect of the electromagnetic pulse (EMP) generated during laser–target interaction was assessed on the system, showing no significant effects on the derived signal-to-noise ratio. These proof-of-principle tests highlight the ability of calorimetry techniques to measure the absorbed dose for laser-driven proton beams. Full article

Nanohydrogel particles of polyethylene glycol (PEG), gelatin (GEL), and PEG–GEL mixtures (MIXs) were synthesized with a high electron beam and ⁶⁰Co gamma-ray radiation. The relatively novel technique of Asymmetrical Flow Field Flow Fractionation (AF4 or AFFFF) coupled to a Multi-Angle Laser Light Scattering (MALLS) detector was mainly used to determine the hydrodynamic diameter (D_h) of the radiation-synthesized PEG, GEL, and PEG–GEL nanohydrogel particles. Our approach to achieving nanohydrogel particles is to enhance the intracrosslinking reactions and decrease the intercrosslinking reactions of the C-centered radicals of the PEG and GEL. The intracrosslinking reactions of these free radicals were enhanced via irradiation at temperatures of 77–80 °C and using a high dose rate and pulsed irradiation. The shorter average distance between the C-centered free radicals on the backbone of the thermally collapsed PEG and GEL chain, due to the destruction of hydrogen bonds, enhances the intracrosslinking reactions. It was observed that increasing the dose and dose rate decreased the D_h. DLS results lined up with AF4 measurements. This study provides researchers with a clean method to produce GEL–PEG hydrogels without the use of toxic reagents. Particle size can be tuned with dose, dose rate, and temperature as demonstrated in this work. This is ideal for medical applications as the use of ionizing radiation eliminates toxicity concerns and provides simultaneous sterilization of the material. Full article

The laser extinction method (LEM) is particularly suitable for measuring particle sizes in flames because this method, which is based on the Beer–Lambert law, is non-intrusive and easy to implement. In the LEM, the interpretation of the extinction data is usually developed under the assumption that light extinction due to scattering is a result of the superposition of single scattering by individual particles; however, this could be violated for flames with dense concentrations of particles in which multiple scattering could occur. Quantifying the effect of multiple scattering under general conditions is still a formidable problem. In this work, we carried out a series of careful measurements of the laser extinction using standard particles of various known sizes, number densities and optical path lengths, all under the condition that the acceptance angle of the detector was limited to nearly zero. Combined with a four-flux model, we quantitatively analyzed the effect of multiple scattering on the size measurement using the LEM. The results show that the effect of multiple scattering could be ignored when the optical thickness is less than two under strict restrictions on the detector acceptance angle. Guided by this, the size distribution of an alumina (${\mathrm{Al}}_2{\mathrm{O}}_3$) particle sample was measured by the LEM with dual wavelengths. Parameterized distributions were solved with the help of graph plotting, and the results compared well with the measurement from the Malvern particle size analyzer. The same method was then used to measure the particle size distribution in the plume of a solid rocket motor (SRM). The use of an off-axis parabolic mirror in the experimental setup could suppress the jitter of light passing through the SRM plume, and the particle size in the plume of the measured SRM was in the order of microns. Full article