Luke Watson | Searcharxiv

arXiv2026

Position Resolution of a Scintillator Hodoscope Employing Triangular Counters with Embedded Wavelength Shifting Fibers

Scintillator counters employing embedded wavelength-shifting fibers have been used in particle physics experiments for several decades. Such counters have been produced with square, rectangular, and triangular profiles. An advantage of arrays of triangular counters is that their position resolution can be greatly enhanced by interpolation between adjacent counters using their relative light yields. We report here on a testbeam study of the position resolution of such a scintillator hodoscope and compare the results to a simulation. We find an order of magnitude improvement in the position resolution over that found by simply using the fiber separation.

physics.ins-det↗

arXiv2024

Selective tracking of charge carrier dynamics in CuInS2 quantum dots

CuInS2 quantum dots have been studied in a broad range of applications, but despite this, the fine details of their charge carrier dynamics remain a subject of intense debate. Two of the most relevant points of discussion are the hole dynamics and the influence of Cu:In synthesis stoichiometry on them. It has been proposed that Cu-deficiency leads to the formation of Cu2+, affecting the localization of holes into Cu defects. Importantly, it is precisely these confined hole states which are used to explain the interesting photoluminescence properties of CuInS2 quantum dots. We use static X-ray spectroscopy to reveal no evidence for a measurable amount of native Cu2+ states in Cu-deficient samples. Instead, the improved properties of these samples are explained by an increase of crystallinity, reducing the concentration of mid gap states. Furthermore, to understand the charge carrier dynamics, herein we employ ultrafast optical transient absorption, and fluorescence up-conversion spectroscopies in combination with ultrafast X-ray absorption spectroscopy using a hard X-ray free electron laser. We demonstrate that in non-passivated samples, holes are transferred from Cu atoms in sub-picosecond timescales. We assign this transfer to occur towards the thiol-based ligands. Finally, we observe that Cu-deficient samples are more robust against the photothermal heating effects of using higher laser fluences. This is not the case for the stoichiometric sample, where heating effects on the structure are directly observed.

physics.chem-ph↗