Intense Source Research Articles

Prospects for the Implementation of an Intense Source of Ultraviolet Radiation Based on a Gas-Discharge Plasma in a Quasi-Optical Cavity Excited by a Pulse of Terahertz Radiation

An electrodynamic system is described that provides the creation of an electromagnetic wave field of high intensity at a frequency of 1 THz due to a combination of accumulation in time and compression in space of a wave pulse coming from an electron cyclotron maser (gyrotron). This system is based on the use of a three-mirror cavity consisting of two focusing mirrors and one flat corrugated Bragg-type photonic structure providing coupling between the gyrotron wave pulse and the operating wave of the cavity. The aim of this work is to use a “spot” of the intense terahertz field inside the cavity to provide a point-like plasma discharge in a gas stream injected into this spot; such a discharge can be a source of extreme ultraviolet radiation.

Advances in Nuclear Data and Software Development for the HighNESS Project

The European Spallation Source, which is under construction in Lund, Sweden, aims to be the world’s brightest source of neutrons. During the first phase of construction, users will have access to a suite of 15 instruments, which will produce neutrons through a butterfly-shaped moderator system located above the spallation target. The HighNESS project, funded by the European Union Horizon 2020 program, has the goal of providing a new design for the second moderator, which will be situated below the spallation target and will be the most intense neutron source in the world. The new moderator will provide a higher intensity of neutrons in the cold, very cold, and ultracold energy regions, which will advance research in several areas of condensed matter and offer unique opportunities in fundamental physics. Work Package 2 of the HighNESS project is focused on supporting the design of the second moderator by providing nuclear data support for neutronics calculations and improving the accompanying physics software. This paper showcases recent advancements in NJOY + NCrystal, a tool for creating thermal neutron scattering–evaluated nuclear data files and continued work on nanodiamonds as advanced neutron reflectors.

Sub-Millimeter Hard X-Ray Source Based on Wire-Shorted Low-Impedance Rod Pinch Diode

Rod pinch diode (RPD) is an intense X-ray point source with a millimeter spot diameter, tens of nanosecond pulsewidth, and tens of keV to MeV photon energy, resulting in extraordinary flash radiography performance. Classical RPD is featured with a high-impedance vacuum gap between the annular cathode and the central anode rod, which limits the electron current and electrical power density, therefore is not conducive to the improvement of brightness. Plasma prefilling can effectively reduce the RPD impedance, thereby increasing the electron current and realizing an impedance match of RPD with low-impedance, high-power-density drivers. In this article, an experimental study on plasma-prefilled RPD is carried out based on a fast linear transformer driver (FLTD) with relatively low charging voltage; the RPD anode and cathode are initially connected by metal wires, which are transformed into plasma shortly after the onset of discharge current. A quasi-spherical X-ray spot is obtained with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 0.45 mm diameter, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim$</tex-math> </inline-formula> 30 ns pulsewidth, 0.6 rad@1 m (LiF) dose, and 55–60 keV equivalent mono-energy photon energy. The radiography performance is further characterized by a tungsten rolled-edge and slit plate. The preliminary results proved the feasibility of low-impedance RPD as a flash radiography source within the relatively low photon energy range.

Optically induced ultrafast magnetization switching in ferromagnetic spin valves.

The discovery of spin-transfer torque (STT) enabled the control of the magnetization direction in magnetic devices in nanoseconds using an electrical current. Ultrashort optical pulses have also been used to manipulate the magnetization of ferrimagnets at picosecond timescales by bringing the system out of equilibrium. So far, these methods of magnetization manipulation have mostly been developed independently within the fields of spintronics and ultrafast magnetism. Here we show optically induced ultrafast magnetization reversal taking place within less than a picosecond in rare-earth-free archetypal spin valves of [Pt/Co]/Cu/[Co/Pt] commonly used for current-induced STT switching. We find that the magnetization of the free layer can be switched from a parallel to an antiparallel alignment, as in STT, indicating the presence of an unexpected, intense and ultrafast source of opposite angular momentum in our structures. Our findings provide a route to ultrafast magnetization control by bridging concepts from spintronics and ultrafast magnetism.

Agglomeration of aerosol using small equipment with two small aerial ultrasonic sources

We have developed an ultrasonic agglomeration device that is considerably smaller than previous devices. We used a round-groove small aerial ultrasonic source, which is a compact, intense aerial source of ultrasonic waves. This ultrasonic source generates a large transverse vibration displacement using a circular vibrating plate with a round groove near the tip of the transmission rod, and it produces intense sound waves perpendicular to the vibration plane. In this paper, a compact agglomeration device containing two round-groove small aerial ultrasonic sources was developed, and the agglomeration efficiency was investigated by varying the volume of the device and the input power to the ultrasonic source. The results showed that although this device is small, it has a sufficient agglomeration effect.

Intense Lyman-alpha light source for ultra-slow muon generation

A small-momentum-width muon beam, so-called ultra-slow muon beam, can be generated by laser ionization of muonium. To realize efficient ultra-slow muon generation, the Lyman-alpha and below 360 nm coherent light are required to resonantly excite the muonium from the ground state to 2p and sequentially ionizes excited muonium to the unbound state. At the J-PARC MLF Ultra-Slow Muon beamline, we have successfully generated Lyman-alpha coherent light exceeding 10 μJ using an all-solid-state laser and high-efficiency vacuum ultraviolet light generation technologies. In this paper, we will describe the intense Lyman-alpha light source.

Benchmarking Fast Neutrons Leakage Spectrum From Copper Block With 252Cf Source in Center

Abstract Copper is an important material for the nuclear industry; therefore, the correct copper cross section are essential. This paper deals with benchmarking the fast neutron leakage spectrum from a copper block with an intense 252Cf source. The spectrum was measured by the proton recoil method using a stilbene scintillator and spectrometer with pulse shape discrimination. The room effect was subtracted experimentally by shielding cone and confirmed computationally. Simulations were performed using the MCNP6.2 Monte Carlo code. A detailed study on uncertainties has been made. Consequently, as the main source of uncertainties, the measurement apparatus was determined (namely, calibration and number of iterations—up to 15%). From the parameter uncertainty, the most important effects are connected with the mass of cube material—the thickness of the assembly (up to 2%). The effect of copper density uncertainty is low because density was determined experimentally with low uncertainty. The uncertainty related to parameter uncertainties in source structural components is negligible because even neglection of all components leads to a shift in leakage spectra below 7%. Several copper nuclear data libraries were tested as well, and it was found that the calculation with JEFF-3.3 gives the most discrepant results with a discrepancy of up to 60%. The closest results were obtained with ENDF/B-VIII.0 (below 5 MeV, discrepancy within 10%) and JENDL-4.0 (above 5 MeV, discrepancy within 15%). ENDF/B-VII.1 library is relatively close in the region above 5 MeV (discrepancy within 15%), below 5 MeV the agreement is worse (up to 40% discrepancy).

Valve noise at high pressure ratios

When high pressure air expands through an orifice it can be an intense noise source, which may be hazardous for nearby personnel if it occurs in an unexpected or uncontrolled way. This paper describes a set of measurements that were carried out to validate and calibrate the well-known Beranek semi-empirical prediction method. A number of valve mockups were tested over a range of mass flow rates with pressure ratios up to 11 Bar, so that the model could be used with confidence to extrapolate up to much higher pressures and larger valve sizes. Interpretation of the measured noise data is carried out using an isentropic analysis of the flow, assuming choked conditions in the orifice to infer a jet Mach number and mass flow rate for each test condition. Based on this inferred flow data the sound power scaled as expected with 8th power of jet Mach number, although there were some deviations at high frequencies and for particular valve configurations. It is also shown that for all valves the sound power varied as 1.5th power of mass flow rate, which is in reasonable agreement with the law that is implicit in the Beranek model, and provided a good basis for extrapolating to larger devices.

Aerial intense ultrasonic source integrating the horn and vibrating plate

The components of conventional high-intensity aerial ultrasonic sources, including the horn, longitudinal vibrating resonance bar, and transverse vibrating plates, are usually constructed separately. In this paper, a compact ultrasonic source that integrates all component parts was developed. First, the structure of the ultrasonic source was designed by simulation analysis with the finite element method. Next, an actual ultrasonic wave source was manufactured, and its electrical characteristics, vibration characteristics, and sound pressure distribution characteristics were measured. The ultrasonic source formed a strong standing wave sound field in the air, even though the total length was one wavelength of the longitudinal vibration. For an input electric power of 10 W, a high sound pressure in the standing wave sound field of 3.44 kPa was obtained (sound pressure level of about 165 dB).

Surface modification of alloys by high-energy pulsed particle beams

The effect of particle beams on the surface of alloys is often used to obtain a material with desired characteristics. Mathematical modeling of such surface modification leads to the study of diffusion in the presence of an intense external source of diffusant. In this case peculiarities in material structure may be of great importance. A special role belongs to inter-grain boundaries in metals, the vicinities of which are regions of accelerated diffusion. Moreover, if the surface treatment by particle beam is carried out with short impulses comparable with relaxation times of diffusion and chemical processes to their equilibrium course, it may be necessary to explicitly consider the particle transfer rate in the material, for example, using the non-classical laws.In this paper we discuss the model of the treatment process by particle beam, which takes into account both the feature of grain boundary diffusion and finiteness of relaxation times of diffusion fluxes in the boundaries and in the volumes of grains. The problem is considered in two-dimensional formulation. The grains and their boundaries are treated as separate phases with different diffusion properties. The grains are represented in the form of rectangles, located at equal distances from each other. The relative size of the boundary phase may vary. Using generalized equations for diffusion fluxes with finite time of relaxation, we come to diffusion equations of hyperbolic type for the volume and the grain-boundary phases. It is assumed that between the diffusant and the treated material a summary chemical reaction occurs with formation of a summary product. A numerical study allowed us for the first time to establish the features of grain-boundary diffusion and to study the dynamics of reaction product formation for treatment times comparable to relaxation times. The effect of pulse duration and grain size on the diffusant concentration distribution for these conditions was investigated.

Intense continuous cold-atom source

We demonstrate an intense, continuous cold atom beam generated via post nozzle seeding of a supersonic helium jet with $^7$Li atoms. The nozzle is cooled to about 4.4 K to reduce the forward velocity of the atoms. The atomic beam is brought to a focus 175 cm from the nozzle by a 10 cm bore diameter magnetic hexapole lens. Absorption and fluorescence imaging of the focus show a flux of $2.3(4) \times 10^{12}$ atoms/s, brightness of $4.1(7)\times 10^{19}$ $\textrm{m}^{-2}\textrm{s}^{-1}\textrm{sr}^{-1}$, forward velocity of 211(2) m/s, and longitudinal temperature of 7(3) mK. Results agree with a Monte Carlo simulation of the seeding dynamics and a particle tracing simulation of the atom lens. We project that 10 times higher flux would be possible with improved vacuum system design. Our method should provide a useful high-brightness source for atom-optical and other atomic and molecular physics applications.

Efficient combination and enhancement of high-power mid-infrared pulses in plasmas

High-power intense optical sources in the mid-to-long wavelength infrared region are very attractive for a wide range of fields from fundamental research to materials science and biology applications. However, there are still significant challenges in extending long-wavelength infrared pulses into the relativistic regime using conventional optical techniques. Here, based upon a new type of plasma-based optical method, we present an efficient scheme capable of combining several high-power long-wavelength infrared laser pulses into one single, more intense pulse, thus bringing the intensity of the output pulse to the relativistic regime. Such intense infrared pulses will open up new possibilities for strong-field physics and ultrafast applications. Furthermore, this is beneficial to understand the underlying physics and nonlinear processes of modulation, propagation and energy transfer of high-power intense laser pulses in plasmas.

Intense and Superflat White Laser with 700-nm 3-dB Bandwidth and 1-mJ Pulse Energy Enabling Single-Shot Subpicosecond Pulse Laser Spectroscopy.

An optical spectrometer is a basic spectral instrument that probes microscopic physical and chemical properties of macroscopic objects but generally suffers from difficulty in broadband time-resolved measurement. In this work, we report the creation of ultrabroadband white-light laser with a 3-dB bandwidth covering 385 to 1,080 nm, pulse energy of 1.07 mJ, and pulse duration of several hundred femtoseconds by passing 3-mJ pulse energy, 50-fs pulse duration Ti:Sapphire pulse laser through a cascaded fused silica plate and chirped periodically poled lithium niobate crystal. We utilize this unprecedented superflat, ultrabroadband, and intense femtosecond laser light source to build a single-shot (i.e., single-pulse) subpicosecond pulse laser ultraviolet-visible-near-infrared spectrometer and successfully measure various atomic and molecular absorption spectra. The single-shot ultrafast spectrometer may open up a frontier to monitor simultaneously the ultrafast dynamics of multiple physical and chemical processes in various microscopic systems.

An Evaluation Model of Star Sensor Observation Capability Under Hypersonic Aerothermal Conditions

During hypersonic flight in the atmosphere, severe aerothermal effects occur on the optical hood or observation window of an aircraft, keeping the optical window and surface flow field in a high-temperature state, as well as causing a large amount of radiation and strong background noise. These phenomena have serious effects on the observation capability of star sensors. An evaluation model of star sensor observation capability under hypersonic aerothermal conditions was constructed in this study, using a definition of the signal-to-noise ratio considering defocused intense radiation sources. Furthermore, a method of calculating the observable limiting magnitude under aerothermal conditions is given. The model was used in simulation tests involving different flight states and temperature conditions. The results showed that the thermal radiation of the aircraft observation window has the greatest influence, which is more than two orders higher than that of the outer flow near the window; when the window temperature was controlled below 750 K, for a star sensor with an SNR threshold of 3, navigation stars with magnitudes brighter than 5 could be captured in the visible band of 0.35– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.7~\mu \text{m}$ </tex-math></inline-formula> , and the near-infrared band of 0.9– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.4~\mu \text{m}$ </tex-math></inline-formula> was unavailable.

JRC MONNET – the intense fast-neutron source for fundamental and application-driven research

MONNET is a fast-neutron source based on a 3.5 MV tandem accelerator, located at the Geel (BE) site of the Joint esearch Centre. It became operational in 2020. MONNET may deliver intense neutron beams in the energy range from 30 keV to 10.1 MeV and from 12.8 MeV to 24 MeV. Neutrons are generated by means of nuclear reactions in the target material (e.g. protons or deuterons on lithium-7, tritium or deuterium targets). MONNET delivers a neutron flux of up to 109 n/sr/s, depending on the producing reaction and the neutron energy. Neutron beams are essentially mono-energetic (∆En/En &lt; 6% with En &gt; 300 keV). The accelerator may also be used with proton and deuteron beams. Alpha beams will be offered soon. Photon beams are possible and presently under investigation. The research program ranges from cross section measurements, e.g. (n, f), (n, p), (n, α) as well as (p, p′), (p, n) and (p, γ), nuclear fission research, material studies (e.g. radiation-induced damage), to the investigation of advanced methods in nuclear technologies, safety and security. The MONNET neutron source offers beamtime to external user within the JRC EUFRAT Open Access program. Proposal evaluation by an independent panel is taking place up to two times per year.

Ultra-high phase-locked harmonic generation from magnetic transversal confinement of electrons

The technological refinements on high-power laser systems of Petawatt class unveil scenarios for light-matter interaction beyond the laser-plasma perspective. In this contribution we explore the possibility of assisting high-harmonic generation (HHG) with the strong magnetic field associated with one of those intense sources. Recently, there has been an interest in developing schemes to employ intense laser beams to define spatial volumes in which strong magnetic fields are found isolated from the electric field. In this conditions, the magnetic field can be used to assist the harmonic generation from atoms from standard drivers. We demonstrate that, using the proper interaction geometry, the magnetic field confines the transversal dynamics of the con-tinuum electrons allowing, on one side, to enhance the efficiency of the electron rescattering that produces the harmonic radiation and, on the other side, to excite the electron transverse dynamics and to convert this energy into phase-locked harmonic photons of few hundreds of eV.

Deuterated Clathrate Hydrates as a Novel Moderator Material for Very Cold Neutrons. Project Aperçu and First Results

Clathrate hydrates are water-based solids with large crystallographic unit cells that show promise as potential moderators for use in new, more intense sources of very cold neutrons (VCN), which would enhance neutron scattering techniques and increase sensitivity of particle physics experiments. These so-called inclusion compounds seem particularly suitable for this application due to the low-energy modes of guest molecules encaged in nano-voids formed by a crystalline network of hydrogen bonded water molecules. In this article we present first results of an ongoing, extensive experimental campaign with the aim of characterizing the scattering properties of deuterated clathrate hydrates relevant for moderator applications. Experiments include neutron diffraction (carried out at Institut Laue-Langevin (ILL) using the instrument D20), as well as measurements of the temperature-dependent dynamical structure factorS(q, ω) in absolute units (carried out on ILL’s Panther and IN5). These measurements will serve as a benchmark for development of new scattering kernels.

Spatial and temporal variation of methane emissions in the coastal Balearic Sea, Western Mediterranean

Methane (CH4) gas is the most important GHG after carbon dioxide, with open ocean areas acting as discreet CH4 sources and coastal regions as intense but variable CH4 sources to the atmosphere. Here, we report CH4 concentrations and air-sea fluxes in the coastal area of the Balearic Islands Archipelago (Western Mediterranean Basin). CH4 levels and related biogeochemical variables were measured in three coastal sampling sites between 2018 and 2021, with two located close to the densely populated island of Mallorca and one in a pristine area in the Cabrera Archipelago National Park. CH4 concentrations in seawater during the study period ranged from 2.7 to 10.9 nM, without significant differences between the sampling sites. Averaged estimated CH4 fluxes during the sampling period for the three stations oscillated between 0.2 and 9.7 μmol m−2 d−1 according to a seasonal pattern and in general all sites behaved as weak CH4 sources throughout the sampling period.

Pile driving noise induces transient gait disruptions in the longfin squid (Doryteuthis pealeii)

Anthropogenic noise is now a prominent pollutant increasing in both terrestrial and marine environments. In the ocean, proliferating offshore windfarms, a key renewable energy source, are a prominent noise concern, as their pile driving construction is among the most intense anthropogenic sound sources. Yet, across taxa, there is little information of pile driving noise impacts on organismal fine-scale movement despite its key link to individual fitness. Here, we experimentally quantified the swimming behavior of an abundant squid species (Doryteuthis pealeii) of vital commercial and ecological importance in response to in situ pile driving activity on multiple temporal and spatial scales (thus exposed to differing received levels, or noise-doses). Pile driving induced energetically costly alarm-jetting behaviors in most (69%) individuals at received sound levels (in zero to peak) of 112-123 dB re 1 µm s-2, levels similar to those measured at the kilometer scale from some wind farm construction areas. No responses were found at a comparison site with lower received sound levels. Persistence of swimming pattern changes during noise-induced alarm responses, a key metric addressing energetic effects, lasted up to 14 s and were significantly shorter in duration than similar movement changes caused by natural conspecific interactions. Despite observing dramatic behavioral changes in response to initial pile driving noise, there was no evidence of gait changes over an experiment day. These results demonstrate that pile driving disrupts squid fine-scale movements, but impacts are short-lived suggesting that offshore windfarm construction may minimally impact the energetics of this ecologically key taxon. However, further work is needed to assess potential behavioral and physiological impacts at higher noise levels.

Generator for Large Fluxes of Kaons and Pions Using Laser-Induced Nuclear Processes in Ultra-Dense Hydrogen H(0)

Laser-induced nuclear reactions in ultra-dense hydrogen H(0) produce mesons with both relatively low kinetic energy and with high kinetic energy. The kaons have up to 100 MeV of kinetic energy, thus a velocity of 0.55 c. Each laser pulse of &gt;0.1 J of energy and length of 5 ns produces 1013 mesons. The operation of the meson generator is here demonstrated by measuring all decay times for mesons in the ns range after induction by a pulsed laser. These decay times are the unique fingerprints of the mesons, and they also produce the kinetic energy of the mesons created from their time-dilated decay. The charged pion decay time at rest from this generator is measured to be 25.92 ± 0.04 ns (standard fit error), in reasonable agreement with the tabulated results of 26.033 ns. A similar accuracy is found for the other mesons as for the charged kaons, with 96 MeV of kinetic energy, at 14.81 ± 0.05 ns. The same general behaviour is found with both deuterium and normal hydrogen forming the ultra-dense phase H(0) on the laser target. This meson generator gives intense meson showers useful for many types of particle physics experiments at a small fraction of the cost of using particle accelerators. A particle accelerator would need an energy of at least 1021 eV to produce a similar shower of 1013 mesons. Thus, the described generator is among the most intense meson sources that exist. Other important applications include nuclear energy generation and particle (pion) radiation for cancer treatment.