High-intensity Source Research Articles

Single-backlighter time-framed X-ray imaging diagnostics of laser plasma using a quasi-coaxial multi-channel Kirkpatrick–Baez microscope

The time-resolved backlight imaging of plasma is crucial for diagnosing density-dependent plasma information. It requires a high-intensity X-ray source and efficient optics. We propose a quasi-coaxial, multi-channel Kirkpatrick–Baez (KB) structure that realizes high-brightness illumination. The angles between the observation axes of neighboring images were significantly reduced. An X-ray multilayer was optimized to enable the system to simultaneously function at two quasi-monochromatic energies to observe the plasma regions of varying densities. Eight-frame high-spatiotemporal-resolution images were obtained with an X-ray backlighter in ShenGuang-III prototype laser facility. This study reports the optical design, multilayer fabrication, and experiments of the proposed microscope.

Measurement of relative neutron energy response curve of plastic scintillator detector based on the back-n-white neutron source at CSNS

The plastic scintillator detector is widely used to measure pulsed radiation fields, and a high-quality neutron energy response curve is crucial for accurately determining neutron yields. Traditionally, the neutron energy response curve can be obtained by the simulation of the performance of neutron detectors via the knowledge of the light yield of secondary particles or direct measuring energy response. Both methods record signals by a data acquisition system in the counting mode. This work establishes a new model to directly measure the energy response to neutrons of a plastic scintillator detector in current mode with white source spectra. The plastic scintillator detector can be triggered externally. There is no signal loss and dead time, and it is possible to calibrate the neutron detector with a high-intensity neutron source. Efficiencies can be determined at all energies simultaneously, and a rapid calibration of the plastic scintillator detector is available. To validate the experimental results, the theoretical values are obtained by Geant4 simulation, and the results reproduce the shapes of the experimental curves reasonably well. The neutron energy response curves of the detector show that when the thickness of the scintillator is reduced from 3 to 1 mm, the reduction ratio of gamma signal intensity is greater than that of neutron signal intensity, which leads to an increase in the neutron–gamma sensitivity ratio. Meanwhile, the thin scintillator thickness can obtain a somewhat flatter neutron energy response curve compared with other thicknesses.

Validation of GEANT4 simulation for active materials interrogation using nuclear resonance fluorescence

This study validates the GEANT4 simulation toolkit's effectiveness in modeling Nuclear Resonance Fluorescence (NRF) for Non-Destructive Assay (NDA) applications, focusing on isotopes 11B and 238U, which exhibit distinct NRF characteristics. Using experimental data from the High-Intensity γ-ray Source (HIγS) facility, the study benchmarks GEANT4's capability in simulating critical NRF interactions, such as spectra peak positions, angular distributions, and yield dependencies on target thickness. For 11B, GEANT4 successfully replicated NRF peaks at 2125, 4440, and 5020 keV, achieving alignment within ±1% of experimental values. For 238U, simulations reproduced NRF yield saturation as target thickness increased, validating the toolkit's handling of self-absorption and scattering effects, which are critical for applications involving high-density, shielded materials. These findings confirm GEANT4's robustness in simulating NRF phenomena, making it suitable for designing advanced NDA systems for security applications where isotope-specific detection and effective shielding penetration are essential. The validated toolkit provides a reliable foundation for developing accurate, efficient, and secure nuclear detection technologies.

Radioxenon beta-gamma coincidence efficiency for a SAUNA detector by Geant4 simulation

A simulation for SAUNA II detector was carried out using the GEANT4 platform. The results demonstrated the accuracy of the simulation, which was well consistent with the experimental results. The simulation was used to calculate the coincidence detection efficiency of each radioxenon isotope, as well as to calculate the resolution for conversion electron peaks. Furthermore, using a 137Cs point source, the simulation was also utilized to perform the beta detector calibration procedure in two scenarios: first, the 137Cs was placed close to the middle of the plastic scintillator, and second, the 137Cs was placed outside the NaI(Tl) detector. The results showed that the spectrum in the first case is better; the source is closer to the plastic detector, leading to maximum Compton scattering. In the second case, a line in the spectrum disappears, so a high-intensity source is needed. Several methods exist to determine the coincidence detection efficiency of the detector. The recommended approach is to determine the total detection efficiency for different regions of interest. The simulation was also used to investigate the effect of replacing helium with nitrogen as a xenon-carrier gas, with the nitrogen resulting in a slight improvement in coincidence detection efficiencies and conversion electron resolution.

Resonant neutron scattering lengths.

Unlike most of the periodic table, many rare-earth elements display considerable resonant scattering for thermal neutrons. Although this property is accompanied by strong neutron absorption, modern high-intensity neutron sources make diffraction experiments possible with these elements. Computation of scattering intensities is accomplished by fitting the variation in resonant scattering lengths (b 0, b' and b'') to a semi-empirical Breit-Wigner formalism, which can be evaluated over the range of neutron energies useful for diffraction, typically E = 10-600 meV; λ = 0.4-2.8 Å (with good extrapolation to longer wavelengths).

First production of X-rays at the ThomX high-intensity Compton source

First production of X-rays at the ThomX high-intensity Compton source

Extended X-ray Absorption Fine Structure (EXAFS) Measurements on Alkali Metal Superatoms of Ta-Atom-Encapsulated Si16 Cage.

The silicon cage nanoclusters encapsulating a tantalum atom, termed Ta@Si16, exhibit characteristics of alkali metal "superatoms (SAs)". Despite this conceptual framework, the precise structures of Ta@Si16 and Ta@Si16+ remain unclear in quantum calculations due to three energetically close structural isomers: C3v, Td, and D4d structures. To identify the geometrical structure of Ta@Si16 SAs, structural analysis was conducted using extended X-ray absorption fine structure (EXAFS) with a high-intensity monochromatic X-ray source, keeping anaerobic conditions. Focusing on "superordered" films, which constitute amorphous thin films composed solely of Ta@Si16 SAs, this analysis preserved locally ordered structures. Spectral comparisons between experimental and simulated Ta L3-edge EXAFS unveil that Ta@Si16 SAs on a substrate adopt a C3v-derived structure, while Si K-edge EXAFS introduces spectral ambiguity in structural identifications, attributed to both intracluster and intercluster scatterings. These findings underscore the significance of locally ordered structure analyses in understanding and characterizing novel nanoscale materials.

A high-intensity low-frequency acoustic generator based on the Helmholtz resonator and airflow modulator.

The high-intensity low-frequency acoustic sources have essential applications in acoustic biological effects research, airport bird repelling, and boiler ash removal. However, generating high-intensity low-frequency acoustic waves in open space is difficult. In this paper, a low-frequency acoustic generator with a resonant cavity used to enhance the acoustic intensity in open space was developed, which is an aerodynamic acoustic generator to radiates a high-intensity acoustic wave of 52Hz. Some experiments were carried out to measure this generator's internal flow field and radiated acoustic field characteristics, including the propagation characteristics at 100m. The experimental results show that the resonant enhancement effect is presented near the predetermined resonance frequency, and the enhanced value is about 4dB. The acoustic intensity for 52Hz at 1m position is 124dB. By combining the Helmholtz resonator with the airflow modulator, the airflow resonance in the resonator enhances the air pressure pulsation inside the chamber and increases the disturbance of acoustic radiation to the air. So as to improve the sound intensity and radiation efficiency in the low-frequency range.

Dynamic flyer in barrel imaging via high intensity short-pulse laser.

The thin flyer is a small-scale flying object, which is well known as the core functional element of the initiator. Understanding how flyers perform has been a long-standing issue in detonator science. However, it remains a significant challenge to explore how the flyer is formed and functions in the barrel of the initiator via tabletop devices. In this study, we present dynamic and unprecedented images of flyer in barrel via high intensity short-pulse laser. Advanced radiography, coupled with a high-intensity picosecond laser X-ray source, has enabled the provision of state-of-the-art radiographs in a single-shot experiment for observing micron-scale flyer formation in a hollow cylinder in nanoseconds. The flyer was clearly visible in the barrel and was accelerated and restricted differently from that without the barrel. This first implementation of a tabletop X-ray source provided a new approach for capturing dynamic photographs of small-scale flying objects, which were previously reported to be accessible only via an X-ray phase-contrast imaging system at the advanced photon source. These efforts have led to a significant improvement of radiographic capability and a greater understanding of the mechanisms of "burst" of exploding foil initiators for this application.

Towards a high-intensity muon source

A high-intensity muon source driven by a continuous-wave superconducting linac holds the potential to significantly advance the intensity frontier of muon sources. Alongside advancements in accelerator technologies, breakthroughs in muon production target and collection schemes are essential. After a brief introduction to the development of the accelerator-driven system superconducting linac, a novel muon production target is proposed, utilizing a free-surface liquid lithium jet capable of handling the heat power generated by a proton beam with an energy of 600 MeV and a current of 5 mA. It is predicted by our simulation studies that the lithium target is more efficient in surface muon production compared to the rotating graphite target. The parameter space of the front end consisting of a lithium target and a large-aperture capture solenoid is explored, from the perspective of production efficiency, capture efficiency, and characteristics of the surface muon beam. Published by the American Physical Society 2024

Microscopic Imaging on Diesel Spray and Atomization Process

Improving diesel engine performance requires a comprehensive understanding of fuel atomization and air–fuel mixing within the combustion chamber. Numerous studies have been conducted to reduce emissions and enhance diesel engines. However, further investigation is required on the detailed diesel spray process. In this study, we adopted extinction measurement to analyze the effects of a fuel injection pressure range of 300 to 700 bar on spray morphology. For the extinction imaging setup, we utilized a high-intensity continuous LED source along with a diffuser to ensure uniform light distribution. The high-speed extinction and image processing results indicate that increasing the injection pressure from 300 to 700 bar effectively produced a smaller particulate size (15% reduction) and a better air–fuel mixing process. Especially at the end of injection, our results show smaller liquid ligaments (50% reduction) and droplets around the injector tip with higher injection pressure cases.

Spectral Characteristics of Polarization Radiation in the Water Window Range

The high-intensity and monochromatic radiation sources in the water window spectral range are desirable for many applications. One of the potential candidates of soft X-ray sources is polarization radiation produced by a charged particle passing through a thin foil. In the soft X-ray range near the absorption edges of a target material, the real part of dielectric permittivity can exceed unity, and the Tamm–Frank criterion is fulfilled. Thus, two types of radiation are produced: transition and Cherenkov radiation. In this report, we theoretically investigated the spectral characteristics of radiation produced in both cases when the Tamm–Frank criterion is met or not met. We showed the dependences of the spectrum as a function of thickness and the incidence angle. To describe the properties of polarization radiation and the complex dielectric permittivity, the polarization current approach and Henke’s model were used, respectively.

Moderator developments in HighNESS and feedback to compact sources design

The main, high-brightness neutron source for ESS is based on the low-dimensional moderator concept, and will serve the initial suite of neutron scattering instruments. In the HighNESS project several design options have been identified and investigated for a second source for ESS, intended to be complementary to the primary one. The emphasis of this project, completed in September 2023, was on the design of high-intensity sources, delivering Cold, Very Cold (VCN), and Ultra-Cold Neutrons (UCN). Remarkable results include: a cold moderator based on liquid deuterium capable of delivering an intensity close to a factor 10 greater than the ESS upper moderator; a VCN moderator based on solid deuterium at 5 K, surrounded by nanodiamond layers, delivering brightness above 40 Å an order of magnitude higher than a conventional cold moderator placed in the same location; and several design options for UCN sources based on the use of superfluid helium and solid deuterium. The use of these new sources would have a major impact on fundamental physics experiments and neutron scattering techniques. We investigate the possible impact that these concepts can have for compact sources, with particular emphasis on VCN.

Flexible tape-drive target system for secondary high-intensity laser-driven sources.

We present the development of a flexible tape-drive target system to generate and control secondary high-intensity laser-plasma sources. Its adjustable design permits the generation of relativistic MeV particles and x rays at high-intensity (i.e., ≥1 × 1018 W cm-2) laser facilities, at high repetition rates (>1Hz). The compact and robust structure shows good mechanical stability and a high target placement accuracy (<4 μm RMS). Its compact and flexible design allows for mounting in both the horizontal and vertical planes, which makes it practical for use in cluttered laser-plasma experimental setups. The design permits ∼170° of access on the laser-driver side and 120° of diagnostic access at the rear. A range of adapted apertures have been designed and tested to be easily implemented to the targetry system. The design and performance testing of the tape-drive system in the context of two experiments performed at the COMET laser facility at the Lawrence Livermore National Laboratory and at the Advanced Lasers and Extreme Photonics (ALEPH) facility at Colorado State University are discussed. Experimental data showing that the designed prototype is also able to both generate and focus high-intensity laser-driven protons at high repetition rates are also presented.

A standardized approach to identify nonlinearity in fighter jet noise during ground run-ups

High-intensity military sources (explosions, gunfire, fighter jet noise. . . ) fall out of the scope of linearity-based commercial software and international standards. On top of its intrinsic complexity (high temperature supersonic jet, shocks, turbulent eddies, etc), fighter jet engine noise bears additional challenges: turbulent surrounding flow, airframe interference, directionality and tonal components typical of rotating equipment. The absence of a suitable metric to determine the boundary of the nonlinear propagation region can lead to costly mispredictions in the exposure levels for noise abatement procedures and the personnel's safety. The derivative skewness of the time domain signal used as an indicator of spectral reshaping proved effective in setting a threshold to the generation of acoustic nonlinearity for seven firearms. Its application to aircraft noise is here discussed, in order to verify the claim of persistence of nonlinear behaviour at large distances and set the foundations for a common framework contemplating the peculiarities of each military noise source. The experimental data was collected during a series of static ground run-ups of an F-16 military jet aircraft. The results from five engine regimes and two propagation paths are compared with the findings from firearms, existing literature and the solution of a nonlinear acoustic propagation solver.

Development and testing of a fission-like neutron field for dosimetry and instrument calibrations based on deuterium-tritium generator

For nearly five decades, 252Cf sources have been used for testing and calibration over a wide range of neutron detection devices used for nuclear safety and radiation protection. However, the vastly increased cost of 252Cf sources, its short half-life, and concerns about future shortage have prompted nuclear facilities and radiological calibration laboratories that rely on high-intensity neutron sources to seek alternatives. There appear to be no other radionuclide neutron sources that would match “like-to-like” 252Cf performance characteristics, although “fit for purpose” substitutions could be possible. Alternatives of producing a fission-like neutron spectrum based on commercially available deuterium-tritium (D-T) generators, and without any fissionable materials or beryllium, have been explored. This paper describes efforts of designing the spectrum shaping assembly, its construction and installation. The produced neutron field was evaluated both from the perspective of the neutron fluence spectrum and the resulting dosimetric outcome. Finally, it was tested for practical application by examining the response of various health physics instruments and personal monitoring devices in comparison to the response of those devices when exposed to 252Cf. The response of survey-type instruments tested within the prototype, surrogate fission, reference field are acceptably close to their response in the targeted 252Cf field.

Realistic prediction and engineering of high-Q modes to implement stable Fano resonances in acoustic devices

Quasi-bound states in the continuum (QBICs) coupling into the propagating spectrum manifest themselves as high-quality factor (Q) modes susceptible to perturbations. This poses a challenge in predicting stable Fano resonances for realistic applications. Besides, where and when the maximum field enhancement occurs in real acoustic devices remains elusive. In this work, we theoretically predict and experimentally demonstrate the existence of a Friedrich-Wintgen BIC in an open acoustic cavity. We provide direct evidence for a QBIC by mapping the pressure field inside the cavity using a Laser Doppler Vibrometer (LDV), which provides the missing field enhancement data. Furthermore, we design a symmetry-reduced BIC and achieve field enhancement by a factor of about three compared to the original cavity. LDV measurements are a promising technique for obtaining high-Q modes’ missing field enhancement data. The presented results facilitate the future applications of BICs in acoustics as high-intensity sound sources, filters, and sensors.

A Diamond Terahertz Large Aperture Photoconductive Antenna Biased by a Longitudinal Field

The novel design of a terahertz large aperture photoconductive antenna (LAPCA) is reported. It features a longitudinal orientation of the bias electric field within the photoconductive substrate, and has the advantage of a small interelectrode gap, resulting in a higher field for the same applied voltage. The proposed LAPCA configuration has been tested with a nitrogen-doped (∼10 ppm) synthetic monocrystalline diamond, which is a promising material for high-intensity and high-power terahertz sources. Two antennas with different high-voltage electrode realizations were assembled, pumped by a 400 nm femtosecond laser, and tested for THz emitter function. The experimental data are found to be in good correlation with the numerical simulation results. The performance of antennas with the conventional transverse E-field configuration and the novel longitudinal configuration is compared and discussed.

Development of Real-Time Fluorescence CRISPR/Cas12a-Based Detection as a Portable Diagnostic System Using Integrated Circuits

A solution for achieving high-performance measurements in a space-constrained experimental setup was developed as a portable incubating instrument for real-time fluorescence detection of AvrPi9 gene in rice blast fungus by using a calibrated spectrometer in CRISPR-Cas12a detection. The system demonstrates accurate temperature control with low energy consumption and low deviation of ±0.16 °C from the setpoint temperatures, with high sensitivity and accurate detection within 10 min. The CRISPR-Cas12a detection reaction was demonstrated using AvrPi9 PCR product, crRNAs, LbCas12a and fluorescence-quencher reporter incubating at 37 °C for 10 min. Calibrated C12666MA spectrometer with 480 nm and 520 nm LEDs vs HR4000 reference exhibits low RMS of 0.54 and 1.30 and drift of 6.4 nm and 4.84 nm, respectively indicating high accuracy and reliability in fluorescence detection. Fluorescence signals were observed under an LED transilluminator, while real-time analysis was conducted through spectrometric measurements upon excitation by a 480 nm high-intensity blue LED source. Accuracy of detection between positive, non-template and non-target control was reported with no incidence of false positives observed. The instrument exhibits reliable quantitative detection capabilities with a limit of detection of 3.8 ng of DNA targets that are comparable to when running the same reaction on a commercial real-time PCR, with a detection limit of 1 ng. This study demonstrates that the CRISPR-Cas12a detection method represents a significant breakthrough in molecular diagnostics due to its advantages of rapidity, high sensitivity, and convenience allowing for the development of a compact, and energy-efficient platform that can facilitate real-time on-site diagnostics with accurate temperature control.

Streak artifact suppressed back projection for sparse-view photoacoustic computed tomography.

The development of fast and accurate image reconstruction algorithms under constrained data acquisition conditions is important for photoacoustic computed tomography (PACT). Sparse-view measurements have been used to accelerate data acquisition and reduce system complexity; however, reconstructed images suffer from sparsity-induced streak artifacts. In this paper, a modified back-projection (BP) method termed anti-streak BP is proposed to suppress streak artifacts in sparse-view PACT reconstruction. During the reconstruction process, the anti-streak BP finds the back-projection terms contaminated by high-intensity sources with an outlier detection method. Then, the weights of the contaminated back-projection terms are adaptively adjusted to eliminate the effects of high-intensity sources. The proposed anti-streak BP method is compared with the conventional BP method on both simulation and in vivo data. The anti-streak BP method shows substantially fewer artifacts in the reconstructed images, and the streak index is 54% and 20% lower than that of the conventional BP method on simulation and in vivo data, when the transducer number N=128. The anti-streak BP method is a powerful improvement of the BP method with the ability of artifact suppression.