Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28 × 28 × 20 mm 3 (length × breadth × thickness) LaBr 3 :Ce crystal, a 25 × 25 × 20 mm 3 CeBr 3 crystal and a 25 × 25 × 10 mm 3 CeBr 3 crystal. Each crystal was encapsulated and coupled to an array of 4 × 4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133 Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr 3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z-coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr 3 :Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical interface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr 3 :Ce and 5.5% for CeBr 3 . The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively.

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We compare the extreme ultraviolet emission characteristics of tin and galinstan (atomic %: Ga: 78.35, In: 14.93, Sn: 6.72) between 10 nm and 18 nm in a laser-triggered discharge between liquid metal-coated electrodes. Over this wavelength range, the energy conversion efficiency for galinstan is approximately half that of tin, but the spectrum is less strongly peaked in the 13–15 nm region. The extreme ultraviolet source dimensions were 110 ± 25 μm diameter and 500 ± 125 μm length. The flatter spectrum, and −19 °C melting point, makes this galinstan discharge a relatively simple high radiance extreme ultraviolet light source for metrology and scientific applications.

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The results of a systematic study performed on Pb-Sn alloys of concentration 65–35% and 94–6% by weight along with spectra from pure Pb and Sn in the wavelength range of 9.8–18 nm are presented. The dynamics of the Nd:YAG laser produced plasma were changed by varying the focused spot size and input energy of the laser pulse; the laser irradiance at the target varied from 7.3 × 109 W cm−2 to 1.2 × 1012 W cm−2. The contributing ion stages and line emission are identified using the steady state collisional radiative model of Colombant and Tonon, and the Cowan suite of atomic structure codes. The Sn spectrum was dominated in each case by the well-known unresolved transition array (UTA) near 13.5 nm. However, a surprising result was the lack of any enhancement or narrowing of this feature at low concentrations of Sn in the alloy spectra whose emission was essentially dominated by Pb ions.

This paper describes the results of an experimental and theoretical investigation of the physical origin of the visible continuum emission usually observed in the early stages of nanosecond laser ablation of solid materials. It has been suggested, but not confirmed, that the continuum is due to radiative recombination and bremsstrahlung emission. Time and space-resolved emission spectroscopy with an absolutely calibrated spectrometer was used to study the spectral emission in laser ablation of zinc in vacuum at 4.1 J cm -2 using a 8 ns, 1064 nm laser pulse. By modeling the spectral emission with a spectral synthesis code, it has been shown that the continuum emission is primarily due to bound-bound transitions between strongly Stark broadened energy levels. Similarly, it can be concluded that the optical absorption is primarily due to bound-bound transitions.