This work aims to test the concept of an activation detector for pulsed DD fusion neutron sources, based on the production of metastable Br-79m within a LaBr3(Ce) scintillator crystal via (n, n') inelastic scattering. The pulsed neutron source employed is the NX3 Plasma Focus (PF) device operated in deuterium gas, which yields about 10(9) neutrons per shot. A range of D-2 gas pressures, from 1 to 13 mbar are used to vary the test conditions. For the sake of comparison, a beryllium fast-neutron activation detector is used simultaneously with the LaBr3(Ce), and for each NX3 PF shot we derive neutron yield values from both Be and LaBr3(Ce) detectors, denoted Y-n(Be) and Y-n(LaBr). The two detectors are positioned in the equatorial plane (theta = 90 degrees) of the NX3 to expose them to bursts of neutrons with energies close to 2.5 MeV, to simulate a thermonuclear DD fusion source. Overall, the shot-to-shot values of Y-n(Be) and Y-n(LaBr) obtained compare reasonably well. At each D-2 gas pressures the 10-shot averaged values < Y-n(Be)> and < Y-n(LaBr)> are mostly within 10% of one another; for the worst case (10 mbar) < Y-n(LaBr)> is 25% higher than < Y-nBe >. Overall, it is concluded that LaBr3(Ce) scintillation detectors can function as a capable and readily obtainable fast-neutron activation detector for measuring neutron yields from pulsed DD fusion sources.

CsPbBr3 quantum dots (QDs) have recently gained much interest due to their excellent optical and scintillation properties and their potential for X-ray imaging applications. In this study, we blended CsPbBr3 QDs with resin at different QD concentrations to achieve thick films and to protect the CsPbBr3 QDs from environmental moisture. Then, their scintillation properties are investigated and compared to the traditional commercial scintillators, CsI:Tl microcolumns, and Gadox layers. The CsPbBr3 QD-resin sheets show a high light yield of up to 21 500 photons/MeV at room temperature and a relatively small variation in light yield across a wide temperature range. In addition, the CsPbBr3 QD-resin sheets feature a small scintillation afterglow. The CsPbBr3 QD-resin sheets show a negligible trap density for the concentration below 50% weight, indicating that traps might arise from the aggregation of the QDs. The CsPbBr3 QD-resin sheets are also very stable at low irradiation intensities and relatively stable at higher intensities, with higher CsPbBr3 QD concentrations being more stable. Gamma-ray-excited-time-resolved emission measurements at 662 keV showed that the CsPbBr3 QD-resin sheets have an average scintillation decay time between 108 and 176 ns, which are still 10 000 and 6000 times faster than CsI:Tl and Gadox, respectively. Imaging tests show that the CsPbBr3 QD-resin sheets have a mean transfer function of 50% at 2 lp/mm and 20% at 4 lp/mm, comparable to that of commercial Gadox layers. This feature makes CsPbBr3 QD-resin sheets a good candidate for the low-cost, flexible X-ray imaging screens and γ-ray applications.

Zirconium and beryllium fast-neutron activation detectors are used to investigate the DD fusion neutron emission from the NX3 Plasma Focus (PF) device operated in deuterium gas. The differing energy dependence of the Zr and Be activation cross-sections enables an effective neutron energy ${E_{\mathrm{n}}}^{\text{eff}}$ to be inferred from the Zr/Be count ratio for individual PF shots. For the fast-neutron activation detector geometry, the relationship between the Zr/Be count ratio and ${E_{\mathrm{n}}}^{\text{eff}}$ is established by MCNP5 simulation. Zirconium and beryllium detector pairs are positioned at 0° and 90° to the PF axis, so that the anisotropy of the neutron energy is measured from shot to shot. The NX3 PF is operated at 12 kV, corresponding to 7.2 kJ capacitor bank energy. Shots are performed for D2 gas pressures ranging from 1.5 to 10 mbar. The highest neutron yields of ∼109 neutron/shot are observed for 5 mbar D2 gas pressure. Typical effective neutron energies ${E_{\mathrm{n}}}^{\text{eff}}$ for the 0° and 90° directions are ∼2.8 MeV and ∼2.5 MeV, respectively, and the neutron energy-anisotropy remains close to $\Delta E_{\mathrm{n}}\cong 0.3\ \text{MeV}$ over the range of D2 gas pressures investigated. The effect of blocking the forward fast-deuteron beam with an obstacle plate positioned in front of the PF anode is also studied. For this case, shots are performed for D2 gas pressures ranging from 1 to 6 mbar. Insertion of the beam-obstacle plate results in a large reduction in neutron yield, while the effective neutron energy ${E_{\mathrm{n}}}^{\text{eff}}$ increases for both the 0° and 90° directions. The results indicate that DD fusion contributions from thermonuclear or gyrating-particle processes are negligible. The collected results are entirely consistent with beam-target fusion being the dominant mechanism within the plasma pinch and throughout an extended cone on the forward (0°) axis of the NX3 PF.

Lead halide perovskite (LHP) nanocrystals (NCs) have recently attracted attention due to both their high quantum yield and their potential for X-ray imaging applications. In this paper, we investigated the scintillation properties of three different LHP NCs; CsPbBr3, FAPbBr(3), and CsPbI3. The featured NCs exhibited high X-ray excited luminescence (XL) at cryogenic temperatures. While FAPbBr(3) and CsPbI3 NCs display thermal quenching, CsPbBr3 NCs show negative thermal quenching and high XL at high temperatures, with a light yield of 24,000 +/- 2,100 photons/MeV at 300 K. The LHP NCs exhibit a small afterglow and low trap density and exhibit a very fast XL decay time, under 20 ns, faster than those of some currently used commercial scintillators. Overall, CsPbBr3 NCs are the best performing materials investigated here, making them particularly attractive for fast-timing applications such as positron emission tomography or particle detectors in high-energy physics. In the end, we demonstrate the proof of concept for using a CsPbBr3 NC matrix for imaging applications and the flexibility of NCs for developing microstructure scintillators.

Commensurate Lithium doping of two-dimensional lead halide perovskites leads to improved scintillation properties, with enhanced light yield, narrower energy resolution, higher radiation hardness and faster scintillation decay.

This paper is a sequel to the 1998 review paper “Scientific status of the Dense Plasma Focus” with 16 authors belonging to 16 nations, whose initiative led to the establishment of the International Center for Dense Magnetized Plasmas (ICDMP) in the year 2000. Its focus is on understanding the principal defining characteristic features of the plasma focus in the light of the developments that have taken place in the last 20 years, in terms of new facilities, diagnostics, models, and insights. Although it is too soon to proclaim with certainty what the plasma focus phenomenon is, the results available to date conclusively indicate what it is demonstrably not. The review looks at the experimental data, cross-correlated across multiple diagnostics and multiple devices, to delineate the contours of an emerging narrative that is fascinatingly different from the standard narrative, which has guided the consensus in the plasma focus community for several decades, without invalidating it. It raises a question mark over the Fundamental Premise of Controlled Fusion Research, namely, that any fusion reaction having the character of a beam-target process must necessarily be more inefficient than a thermonuclear process with a confined thermal plasma at a suitably high temperature. Open questions that need attention of researchers are highlighted. A future course of action is suggested that individual plasma focus laboratories could adopt in order to positively influence the future growth of research in this field, to the general benefit of not only the controlled fusion research community but also the world at large.

Two-dimensional lead halide perovskites have demonstrated their potential as high-performance scintillators for X- and gamma-ray detection, while also being low-cost. Here we adopt lithium chemical doping in two-dimensional phenethylammonium lead bromide (PEA) 2 PbBr 4 perovskite crystals to improve the properties and add functionalities with other radiation detections. Li doping is confirmed by X-ray photoemission spectroscopy and the scintillation mechanisms are explored via temperature dependent X-ray and thermoluminescence measurements. Our 1:1 Li-doped (PEA) 2 PbBr 4 demonstrates a fast decay time of 11 ns (80%), a clear photopeak with an energy resolution of 12.4%, and a scintillation yield of 11,000 photons per MeV under 662 keV gamma-ray radiation. Additionally, our Li-doped crystal shows a clear alpha particle/gamma-ray discrimination and promising thermal neutron detection through 6 Li enrichment. X-ray imaging pictures with (PEA) 2 PbBr 4 are also presented. All results demonstrate the potential of Li-doped (PEA) 2 PbBr 4 as a versatile scintillator covering a wide radiation energy range for various applications.

Two-dimensional (2D) hybrid lead halide perovskites are potential candidates for high light yield scintillators as they have small band gaps between 3 and 4 eV and large exciton-binding energy. Here, we discuss the scintillation properties from a total of 11 organic/inorganic hybrid perovskite crystals with two already reported crystals, (PEA)2PbBr4 and (EDBE)PbBr4. Their photoluminescence and X-ray luminescence (XL) spectra are dominated by narrow and broad band emissions, and they correspond to free exciton and self-trapped exciton, respectively. The lifetimes derived from time-resolved XL strongly vary from 0.6 to 17.0 ns. These values make this type of compound among the fastest scintillators. For the light yield derived from the XL, we found that only (PEA)2PbBr4, (EDBE)PbBr4, and (BA)2PbBr4 crystals have light yields between 10,000 and 40,000 photons/MeV. The mechanisms for thermal quenching and afterglow are discussed in order to optimize the light yields. With gamma-ray excitation, we reported the best energy resolution of 7.7% at 662 keV with excellent proportionality. Finally, this study paves the way toward the ultimate high light yield and fast scintillators for medical and homeland security applications.

Due to the large exciton binding energy, two-dimensional perovskite has demonstrated the potential as high-performance while low-cost scintillator. In our experiment, first we systemically investigate the effect of Li-ion dopant in phenethylammonium lead bromide, (PEA)2PbBr4 perovskite crystals under soft X-ray radiation of 15 keV. Successful inclusion of Li at four doping concentrations was confirmed by X-ray photoelectron spectroscopy. Li doping causes no substantial change in the crystal structure judging from the X-ray diffraction pattern but induces stronger emission tail as observed in the temperature-dependent X-ray luminescence (XL). Upon higher Li concentration, the emissions become broader due to possible Li trap emission as indicated by increasing traps induced by more Li in the X-ray thermoluminescence spectra. The behavior of negative thermal quenching is found in the XL and it can yield a benefit such as the possible light yield improvement in the X-ray imaging application. After the soft X-ray characterizations, we further explore our crystals in gamma-ray detection. In the gamma-ray pulse height measurement, relatively broad peaks can be resolved with the light yield of about 10,000 photons/MeV at 662 keV. The result from alpha particle pulse height measurement also indicates that we could even utilize our crystals in alpha particle detection at 5.8 MeV. Based on this feature and Li-ion capability as dopants, our crystals promise a good performance in thermal neutron detection. Finally, we can realize a versatile radiation detector that works in broad range of energy from soft to high energy radiation.

A sub-kilo-Joule plasma focus device (FMPF-3, 14 kV/235 J) was operated with deuterium–krypton admixtures (of 1, 2 and 5 % Kr by volume) to study the influence of admixture ratio on neutron yield (Y n). Experiments were performed for different insulator sleeve lengths and cathode geometries. The results reveal that for a carefully optimized electrode geometry the highest average neutron yield is obtained with pure deuterium as the operating gas, whereas krypton seeding leads to a reduction in Y n. We argue that the electrode geometry and electrical coupling play critical roles in determining the influence of gas admixtures; and that for an optimized plasma focus device D2-Kr admixtures may give little or no neutron yield enhancement relative to pure D2 operation and so the admixture operation is an evaluation methodology to determine the level of optimization of device geometry.

The deuterium-deuterium (DD) fusion neutron yield and anisotropy were measured on a shot-to-shot basis for the NX2 plasma focus (PF) device using two beryllium fast-neutron activation detectors at 0° and 90° to the PF axis. Measurements were performed for deuterium gas pressures in the range 6–16 mbar, and positive correlations between neutron yield and anisotropy were observed at all pressures. Subsequently, at one deuterium gas pressure (13 mbar), the contribution to the fusion yield produced by the forwardly-directed D+ ion beam, emitted from the plasma pinch, was investigated by using a circular Pyrex plate to obstruct the beam and suppress its fusion contribution. Neutron measurements were performed with the obstacle positioned at two distances from the anode tip, and also without the obstacle. It was found that ~ 80% of the neutron yield originates in the plasma pinch column and just above that. In addition, proton pinhole imaging was performed from the 0° and 90° directions to the pinch. The obtained proton images are consistent with the conclusion that DD fusion is concentrated (~ 80%) in the pinch column region.

The spatial distribution of DD fusion in a 1.6 kJ plasma focus (PF) device is investigated using the coded aperture imaging (CAI) technique, enabling single shot fusion images to be obtained. Simultaneously, two beryllium fast-neutron activation detectors are employed to measure neutron yield and anisotropy. The coded mask patterns used are based on Singer cyclic difference sets with various open fractions. The physical mask patterns are laser-machined in stainless steel foil, and CR-39 nuclear track detectors record the coded image of the ~3 MeV DD protons emitted from the PF pinch region. In one series of experiments using pure deuterium, five CAI cameras were employed simultaneously: one positioned on-axis (0°) and four at 45° to the PF axis. For another series of experiments two higher-resolution CAI cameras were positioned at 90° to the PF axis, on opposite sides of the pinch. The PF was operated in either pure deuterium gas or deuterium-krypton admixtures of various concentrations1. For single PF shots, the shape of the fusion emission zone is observed to change between high and low neutron-yield shots; high and low neutron-anisotropy shots; and between pure deuterium and deuterium-krypton admixtures. These results are discussed with regard to PF fusion mechanisms.

The PLANSEE double forged W samples were irradiated at different distances (5, 10, 15 and 20 cm) from the anode top for fixed 50 focus shot using a single shot 10 kJ NX3 plasma focus (PF) device with deuterium as the filling gas. The NX-3 PF device is dri ven by a 100 μF, 20 kJ modular capacitor bank which is capable of delivering peak current in the range of 200 kA to 600 kA depending upon charging voltage. The coaxial electrode assembly of the NX-3 plasma focus head consists of a 140 mm long, cylindrical anode of stainless steel (SS) having diameter of 40 mm and a squirrel cage cathode, consisting of twelve, 12 mm diameter brass rods, uniformly spaced on a coaxial circle of 90 mm diameter. The anode has 110 mm deep cavity of 32 mm diameter to minimize the ablation of anode material. An aluminum double aperture with 1 cm aperture size is used to reduce the anode material from reaching the irradiated PLANSEE double forged W sample surface. The virgin and irradiated samples were analyzed in detail using SEM, EDX, XPS and XRD. The impurity material ablated from anode (Fe and Cr) and aperture (Al) wer e found to be deposited on W substrate surface. This is a serious problem for material irradiation studies as it leads to impurity material deposition on irradiated substrate which should be avoided or minimized to correctly evaluate the effect of fast energetic ions and hot dense decaying plasma on irradiated sample. In order to evaluate that which one, anode or the aperture, is a bigger source of impurity deposition on irradiated substrate another systematic experiment was performed in 3 kJ UNU-ICTP PF facility. Silicon substrates were irradiated using different number of PF shots (1, 5, 10 and 20 shot) at fixed irradiation distance of 6 cm with and without double aperture assembly of bronze (as bronze has greater ablation threshold compared to aluminum). The investigation confirms that the impurities mostly being contributed by contributed by aperture, but only for higher number of irradiation PF shots.

Laser shadowgraphy has been used to investigate the plasma sheath dynamics in a miniature plasma focus device (FMPF-3, 14 kV/235 J). The occurrence of magneto-hydro-dynamics instabilities are compared for pure deuterium versus deuterium–krypton admixture operation, over the range of gas pressures 2–12 mbar. A cathode-less geometry was also tested to study the influence of cathode configuration on current sheath formation and compression. The average neutron yield, measured using 3He proportional counters, is compared for different geometries and gas pressures. The synchronization of the four pseudo-spark-gap switches was found to be a major factor influencing the plasma sheath dynamics and neutron yield. To make a fair comparison of operation with different gas pressures or admixture proportions, the level of switch synchronization must be in the same range. Laser shadowgraphs of early stage dynamics show that poorly synchronized discharges result in asymmetric plasma sheath formation, and asymmetries in the accelerated sheath typically persist till the end of the final compression.

We classify all coded masks onto which cyclic difference sets can be wrapped periodically using a generalization of the Finger and Prince construction. In particular, we establish simple numerical criteria which determine whether any given mask can be wrapped periodically in this way and, for each mask which can, we provide explicit constructions which will produce at least one such wrapping. We show that all periodic wrappings currently reported in the literature are special cases of our explicit constructions, and we often provide simpler alternatives. Using these constructions we show that all Singer cyclic difference sets of practical size and open fraction can be wrapped exactly onto masks which are very nearly as compact and symmetrical as hexagons, without the need for pixel padding.

Devices other than the accelerators are desired to be investigated for generating high energy particles to induce nuclear reaction and positron emission tomography (PET) producing radioisotopes. The experimental data of plasma focus devices (PF) are studied and the activity scaling law for External Solid Target (EST) activation is established. Based on the scaling law and the techniques to enhance the radioisotopes production, the feasibility of generating the required activity for PET imaging is studied.

This paper presents the synthesis of iron oxide nanoparticles using the atmospheric microplasma (AMP). The properties of iron oxide nanoparticles synthesized using AMP are compared with particles (i) formed in as-prepared solution and (ii) prepared using thermal decomposition method. Iron oxide nanoparticles prepared by all the 3 treatment methods exhibit quite soft ferromagnetic properties with coercivities less than 10 G. The AMP synthesis technique was found to be more efficient and better than thermal decomposition method due to ultra-shorter experiment time (around 2.5 min) as compared to 90 min required for thermal decomposition method. Moreover, AMP synthesized nanoparticles are better isolated and of smaller size than thermal decomposition ones. The effect of plasma discharge timings on synthesized nanoparticles has also been studied in this work. Coercivity of synthesized nanoparticles decreases with the increasing plasma discharge timings from 3 to 10 min. The nanoparticles synthesized using plasma discharge timing of 10 min exhibit the smallest coercivity of around 3 G. This suggests a high possibility of achieving super-paramagnetic nanoparticles by optimizing the plasma discharge timings of AMP.