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)2PbBr4 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)2PbBr4 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 6Li enrichment. X-ray imaging pictures with (PEA)2PbBr4 are also presented. All results demonstrate the potential of Li-doped (PEA)2PbBr4 as a versatile scintillator covering a wide radiation energy range for various applications.

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 excitonbinding energy. Here, we discuss the scintillation properties from a total of 11 organic/inorganic hybrid perovskite crystals with two already reported crystals, (PEA) 2 PbBr 4 and (EDBE)PbBr 4 . 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) 2 PbBr 4 , (EDBE)PbBr 4 , and (BA) 2 PbBr 4 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.

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.

Published literature shows that the neutron yield of the plasma focus has been modeled in two papers using a thermonuclear mechanism. However, it is more widely held that plasma focus neutrons are produced mainly by nonthermalized mechanisms such as beam-target. Moreover these papers use several parameters which are adjusted for each machine until the computed neutron yield Y n data agree with measured Y n data. For this paper numerical experiments are carried out, using the Lee model code, incorporating a beam-target mechanism to compute the Y n versus pressure data of plasma focus devices PF-400 J and FN-II. The Lee model code is first configured for each of these two machines by fitting the computed current waveform against a measured current waveform. Thereafter all results are computed without adjusting any parameters. Computed results of Y n versus pressure for each device are compared with the measured Y n versus pressure data. The comparison shows degrees of agreement between the laboratory measurements and the computed results.

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.

The average total neutron yield is measured, using an indium foil activation detector, at various combinations of filling gas pressures (including the higher pressure operation regime) of deuterium, capacitor bank charging voltages, anode lengths and insulator sleeve lengths to optimize the neutron yield from the NX2 Plasma Focus device. A remarkable six-fold increase in the average maximum total neutron yield, to a record value of (7 ± 1) × 10 8 neutrons per shot, compared to the similar energy UNU-ICTP Plasma Focus device is achieved for deuterium at a relatively much higher filling gas pressure of 20 mbar. The average peak neutron energy for the axial direction (0˚), radial direction (90˚) and backward direction (180˚) is estimated to be 2.89 ± 0.25 MeV, 2.49 ± 0.20 MeV and 2.11 ± 0.12 MeV, respectively. The average forward to radial neutron yield anisotropy is found to be 1.46 ± 0.28. The neutron energy and anisotropy measurements suggest that the neutron production mechanism may be predominantly beam target.

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; CsPbBr 3 , FAPbBr 3 , and CsPbI 3 . The featured NCs exhibited high X-ray excited luminescence (XL) at cryogenic temperatures. While FAPbBr 3 and CsPbI 3 NCs display thermal quenching, CsPbBr 3 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, CsPbBr 3 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 CsPbBr 3 NC matrix for imaging applications and the flexibility of NCs for developing microstructure scintillators.

A magnetic spectrometer positioned on the axis of a 3 kJ plasma focus device has been used to measure energy spectra of deuterons emitted from the pinch region of the focus, while an indium activation detector was employed to measure the associated neutron flux. Solid-state nuclear track detectors (PM-355) were used in the focal plane of the spectrometer to detect the analysed ions, with multiple spectra being recorded on each detector. An automated track counting system has been developed to read the spectral information from the detectors, which has facilitated the analysis of a far greater number of energy spectra, with greater accuracy, than has been possible in previous work. This automated system comprises an optical microscope with CCD camera, a motorized microscope stage, and image processing and control software. The experimental results show that the deuterons emitted from the pinch region have a continuous spectrum of energies which follow the empirical relationship dN/dE ∝ E −n , where n is typically in the range 6-7. A clear correlation between the measured deuteron energy spectra and neutron flux is observed at each of three working gas pressures investigated.