Ultrafast laser filamentation offers a path to remote material detection and characterization via filament-induced breakdown spectroscopy (FIBS). It has been suggested that the nature of filament-aerosol interactions could enable FIBS measurements through optically complex media such as fog, haze, and clouds. We experimentally investigate the spatiotemporal dynamics of filament-cloud interactions at a kilohertz-scale repetition rate, comparing standard Gaussian and LG 05 Laguerre-Gaussian spatial modes. We demonstrate significant filament-driven cloud-clearing effects that extend over a scale of several millimeters from the filament axis. We further report scattering measurements consistent with filament-induced secondary atomization in liquid aerosols. This fragmentation increases optical attenuation and modifies the clearing dynamics by reducing droplet mass. The filament structure induced by a Gaussian beam is more effective in clearing liquid aerosols than the LG 05 Laguerre-Gaussian beam and exhibits a maximum in transmission at a small lateral displacement from the beam axis. The annular multifilament structure of the Laguerre-Gaussian beam establishes a central core with a refractive index profile compatible with waveguiding in a laboratory cloud environment, offering the prospect of use in applications that require more efficient light collection.

We present a detailed investigation of the temporal evolution of line and continuum emissions in laser-induced breakdown spectroscopy (LIBS) of gaseous uranium hexafluoride (UF6), focusing on the spectral region near 646 nm. Spectral emission features, signal-to-background ratios (SBRs) of selected uranium lines, and spectral linewidths were examined under varying UF6 pressures (15-60 Torr) and laser pulse energies (10-60 mJ). Higher pressures and pulse energies enhanced continuum emission and reduced SBRs but did not cause significant spectral congestion. Additional studies with the use of different laser systems, including nanosecond-pulsed Nd:YAG lasers (at fundamental and various harmonics) and a femtosecond-pulsed Ti:sapphire laser, revealed long-lived plasma continua in all cases. This persistent continuum is attributed to a pseudo-continuum from overlapping molecular emissions, as its intensity scales linearly with electron number density, deviating from the expected quadratic dependence of classical ion-electron interactions for free-free and free-bound continuum emission. Based on plasma persistence time, SBR, U II/U I intensity ratios, and electronic excitation temperature, no fundamental advantage was found for femtosecond-pulsed lasers over conventional nanosecond-pulsed ones for UF6 enrichment assay with direct LIBS measurement.

YAP:Ce is a fast, mechanically robust inorganic scintillator primarily used to detect X-rays and gamma rays. Differences in scintillation kinetics for gamma rays and alpha particles in YAP:Ce have been reported, but particle identification capability through pulse shape discrimination has not previously been shown. Therefore, YAP:Ce has been paired with additional scintillation material such as ZnS(Ag) in mixed-field applications, but the slow decay time of the latter limits these applications to relatively low count rates. This work highlights the limitations of traditional approaches to particle identification in YAP:Ce and demonstrates the efficacy of a machine-learning-based approach. Through a proof-of-concept experiment, we show that this approach offers a possible path towards using YAP:Ce alone to discriminate between alpha particles and gamma rays in mixed-field radiation environments.

The dual neutron/gamma-ray sensitivity of organic scintillators makes them suitable for a wide range of nuclear measurement applications, including nuclear nonproliferation, nuclear medicine, and fundamental physics. Pulse shape discrimination techniques enable distinguishing interactions of different particle types and are typically implemented with simple analog techniques or digital renditions of those techniques. Many new digital techniques for pulse shape discrimination have been proposed, but few have reached wider adoption due to their complexity and computational cost. We introduce a new digital technique for pulse shape discrimination based on traditional charge comparison which uses light output-dependent integration gates to optimize neutron/gamma-ray discrimination without increasing the computational cost of pulse analysis. We assessed the quality of neutron/gamma-ray discrimination by employing this new method in EJ-309, EJ-315, and trans-stilbene organic scintillators using measured data taken with a 252Cf spontaneous fission source. We show an improved or comparable figure of merit of neutron/gamma-ray discrimination across all light outputs over the traditional charge comparison method. The average figure of merit of neutron/gamma-ray discrimination for events with light output between 0.1 MeVee and 3.0 MeVee was increased from 1.20 to 1.28, 1.38 to 1.43, 1.54 to 1.67, and 1.85 to 1.92 for two EJ-309s, an EJ-315, and a trans-stilbene detector, respectively.

Neutron active interrogation is an approach that can identify concealed contraband in cargo, for which chlorine detection can be indicative. We used a pulsed deuterium-deuterium neutron generator to induce chlorine capture gamma rays and measured this signature with a NaI(Tl) inorganic scintillator and organic scintillators analyzed with maximum likelihood estimation-maximization-based spectral reconstruction. The time profile of neutron emission from the neutron generator was also measured using an organic scintillator. We evaluate the signal intensity and signal-to-background ratio for the chlorine gamma-ray signatures for various neutron generator pulse lengths. We demonstrate that decreasing the pulse length can increase the chlorine signal intensity, thereby enhancing sensitivity to chlorine-containing contraband. For example, we show that by decreasing the neutron generator duty factor from 50% to 5%, the chlorine signal intensity measured with NaI(Tl) during the time region between neutron pulses increases from 44.7 +/- 0.3% of the signal intensity without time gating to 99.1 +/- 0.3% of the signal intensity without time gating. We also show that the signal-to-background ratio for chlorine signatures does not decrease by reducing pulse width.

Measurement of the fast neutron production rate in deuterium-tritium (D-T) fusion reactions is important for applications such as active interrogation, fusion diagnostics, and borehole logging. Such measurements are typically performed by neutron activation analysis of metal foils, especially copper. Copper foil activation analysis requires efficiency and energy calibrations of the detector used to measure the foil, and it relies on the detection of 511 keV gamma rays, which are prominent in the active background when neutrons are being produced. Alternatives, such as 79mBr produced by inelastic neutron scattering on 79Br, are limited by short half-life, low-energy gamma emission, and inability to selectively measure D-T neutrons. This work describes a novel alternative approach to measure & Agrave;10 MeV neutron fields based on self-activation analysis of a LaBr3:Ce detector. The activity of 78Br, the activation product of the 79Br(n,2n)78Br reaction, is used to determine the neutron flux and infer the neutron production rate. We experimentally demonstrate the method with a cylindrical LaBr3:Ce crystal with a diameter and height of 3.81 cm that was placed at an similar to 18 cm distance from the neutron production point, at a 90 degrees angle with respect to the deuteron beam in a D-T neutron generator. Operating voltage and current of the generator were adjusted to evaluate the technique's performance over a nominal generator output range of approximately (1-9) x 107 n/s. The neutron output obtained from LaBr3:Ce activation agrees to within three standard deviations of the output obtained using copper activation. The self-activation technique can be conveniently employed in a variety of applications to simplify measurements of fast neutrons produced in D-T fusion reactions.

Cryogenic decay energy spectrometry provides high energy resolution and enables absolute decay counting, offering an alternative measurement technique for radiochronometry. A cryogenic decay energy spectrometry experiment was conducted using a magnetic microcalorimeter to determine the age of a plutonium sample. The energy resolution was measured at 0.05% from 5 to 6 MeV. The time since sample purification was determined using the measured concentration ratio of the 241Am/241Pu radiochronometer. Sample age estimates based on 241Pu alpha-decay and beta-decay counts, along with 241Am decay counts, align with the expected sample age within expanded uncertainty (k = 2), supporting the accuracy of cryogenic decay energy spectrometry as a radiochronometric method.

Safe operation of next-generation nuclear reactors is contingent on developing and effectively operating new diagnostics methods. For helium-cooled fast reactors, one important safety concern is the onset of fuel-cladding failure, which could be detected from the increased concentration of mobile fission fragments such as xenon in the helium coolant. In a previous study [Burger et al., JAAS, 2021, 36, 824], we demonstrated that laser-induced breakdown spectroscopy (LIBS) is a viable candidate for sensitive xenon detection in helium, offering a limit of detection on the order of 0.2 mu mol mol-1 for 104 laser shots. Here, we demonstrate that double-pulse LIBS enhances the xenon signal by approximately 14x at a concentration of 1 mu mol mol-1 in an ambient helium environment, which results in significantly improved sensitivity. Additionally, we examine the effect of relative energy in two laser pulses, interpulse delay, and laser polarization on the xenon signal enhancement. These results further motivate the development of LIBS sensors for this application.

We have produced laser wakefield-accelerated electron beams with energies of 2 GeV in Target Area 1 of the ZEUS facility. These electron beams oscillate in the accelerating structure that is produced in the wake of an ultrashort laser pulse (25 fs). These 'betatron' oscillations result in the emission of a collimated (4 mrad divergence) beam of high-energy X-ray/gamma photons (on the order of several hundred keV). In this work, we demonstrate the capabilities of the ZEUS laser system by showing that apodizing the laser beam in the near field allows for the production of high-quality betatron X-rays for radiography purposes. This demonstrates that a high-power, large-aperture laser beam could be split into multiple parts to drive betatron X-ray sources from multiple angles or temporal delays into a High Energy Density (HED) target to be probed, enabling pump-probe measurements at multiple temporal delays or tomography on a single shot.

We present initial results on nuclear recoil detection based on the fluorescence of color centers created by nuclear recoils in lithium fluoride. We use gamma rays, fast and thermal neutrons, and study the difference in responses they induce, showing that this type of detector is rather insensitive to gamma rays. We use light-sheet fluorescence microscopy to image nuclear recoil tracks from fast and thermal neutron interactions deep inside a cubic-centimeter sized crystal and demonstrate automated feature extraction in three dimensions using machine learning tools. The number, size, and topology of the events agree with expectations based on simulations with TRIM. These results constitute the first step towards 10-1000g scale detectors with single-event sensitivity for applications such as the detection of dark matter particles, reactor neutrinos, and neutrons.

Fast neutron imaging is an important capability for diverse applications such as inertial confinement fusion diagnostics, cargo security, nuclear nonproliferation and arms control, and industrial inspection. Traditional phosphor image plates can be enhanced for fast neutron imaging using hydrogenous plastic converters which allow fast neutrons to scatter off hydrogen nuclei to produce energetic protons that can be recorded by the image plate. However, protons emitted by image plates are not constrained in their emission angle, which contributes to the blur of the resulting image. Here, we investigate two methods that can alter the spatial extent of converted protons that deposit energy in the image plate: reducing the converter thickness, and introducing a proton filter between the plastic converter and image plate to reduce the contribution of lower- energy, off-axis protons to the image. We determine the optimal plastic converter thickness for maximizing the signal intensity to be 2-3 mm through Monte Carlo simulations, and we benchmark this result against experimental measurements with a deuterium-tritium (DT) neutron generator. Next, we evaluate the image smearing and signal loss for various converters to show that solely reducing the converter thickness has the expected effect of reducing the blur from proton image smearing of the sharpness of an edge recorded on the image plate at the cost of reducing the signal intensity. The use of a proton filter is shown to achieve a similar improvement of edge sharpness as reducing the converter thickness while also sacrificing the signal intensity. We conclude that the use of proton energy filtering can improve the sharpness of fast neutron images in situations where the converter thickness cannot be reduced below some practical minimum. For more intense neutron sources, the signal intensity is of less concern, and optimizing the resolution of the image plate and therefore of the imaging system could have greater value. In these applications, proton filters may allow for improved fast neutron imaging measurements.

We experimentally demonstrate enhanced absorption of near relativistic optical vortex beams in $\mathrm{D_2O}$ plasmas to generate a record fast-neutron yield of $1.45 \times 10^6$ n/s/sr. Beams with a topological charge of 5 were shown to deliver up to a 3.3 times enhancement of fast-neutron yield over a Gaussian focused beam of the same energy but having two orders of magnitude higher intensity. This result was achieved with laser energies of 16 mJ and a pulse duration of 67 fs. The Orbital Angular Momentum (OAM) beam-target interactions in our experiment were also investigated through Particle-in-Cell (PIC) simulations. Electron density rippling resulting in enhanced plasma wave excitation on the critical surface and significantly enhanced resonance absorption is observed.

The third “Mineral Detection of Neutrinos and Dark Matter” (MDνDM'25) meeting was held May 20-23, 2025 in Yokohama, Japan, hosted by the Yokohama Institute for Earth Sciences, Japan Agency for Marine-Earth Science and Technology (JAMSTEC). These proceedings compile contributions from the workshop and update the progress of mineral detector research. MDνDM'25 was the third such meeting, following the first in October of 2022 held at the IFPU in Trieste, Italy and the second in January of 2024 hosted by the Center for Neutrino Physics at Virginia Tech in Arlington, USA. Mineral detectors record and retain damage induced by nuclear recoils in synthetic or natural mineral samples. The damage features can then be read out by a variety of nano- and micro-scale imaging techniques. Applications of mineral detectors on timescales relevant for laboratory experiments include reactor neutrino monitoring and dark matter detection, with the potential to measure the directions as well as the energies of the induced nuclear recoils. For natural mineral detectors which record nuclear recoils over geological timescales, reading out even small mineral samples could be sensitive to rare interactions induced by astrophysical neutrinos, cosmic rays, dark matter and heavy exotic particles. A series of mineral detectors of different ages could measure the time evolution of these fluxes, offering a unique window into the history of our solar system and the Milky Way. Mineral detector research is highly multidisciplinary, incorporating aspects of high energy physics, condensed matter physics, materials science, geoscience, and AI/ML for data analysis. Although realizing the scientific potential of mineral detectors poses many challenges, the MDνDM community looks forward to the continued development of mineral detector experiments and the possible discoveries that mineral detectors could reveal.

Laser systems based on coherent beam combination (CBC) that rely on tiled pupil architecture intrinsically carry digital capabilities independently applicable to all three essential characteristics of a laser pulse: amplitude, phase and polarization. Those capabilities allow the far-field energy distribution to be flexibly tailored in real time. Operation in the femtosecond regime at high repetition rates gives access to a wide range of applications requiring both high peak and average powers. We address the task of independent peak versus average power adjustment needed for applications seeking to decouple nonlinear phenomena associated with GW peak power from the thermal load inherent to kW average power operation. The technical solutions proposed are presented in the framework of the Ecole Polytechnique XCAN CBC laser platform (61 independent channels) with an emphasis on thermal management measures implemented to ensure its nominal operation.