Harsh Arya | Searcharxiv

arXiv2026

The Development of a Preclinical Alpha Irradiation Platform with Versatile Control of Dose, Dose Rate, and Spatiotemporal Irradiation Patterns

Objectives. This study develops and validates a vacuum-based alpha irradiation platform to support preclinical radiobiology. We aim to demonstrate precise, independent control over incident energy, fluence rate, and spatiotemporal patterns, which are critical to the mechanisms underlying targeted alpha therapies and low-dose risk assessments. Approach. A vacuum-based system with a radioactive alpha source was designed and fabricated. The platform provides independent modulation of: (i) temporal patterns via a programmable gate valve; (ii) fluence rate across two orders of magnitude by varying source-to-aperture distance (57 to 381 mm); (iii) incident energy (0 to 4.6 MeV) using adjustable absorption layers; and (iv) spatial distributions via a 3D motion stage. Temporal precision was assessed via synchronized audio-electronic recordings. Fluence rates and energies were validated using CR-39 detectors and Monte Carlo (MC) simulations. Spatial precision was verified through programmed continuous and discrete trajectories. Main results. Validation experiments demonstrated high system fidelity. Measured irradiation durations deviated from programmed values by less than 0.3 s. Measured and computed fluence rates agreed within 3%. For energy validation, CR-39 track diameters matched MC model predictions within one standard deviation. Recorded spatial patterns and dimensions aligned well with programmed trajectories. Significance. We successfully validated a versatile vacuum-based platform that overcomes energy-degradation constraints of gas-filled systems. By providing multi-parametric control over alpha-particle delivery, this system enables systematic investigation into how energy, dose rate, and spatiotemporal patterns influence radiobiological responses. This platform is poised to optimize targeted alpha therapies and refine radiation protection frameworks.

physics.med-ph↗

arXiv2023

Ab initio study of the structure and properties of amorphous silicon hydride from accelerated molecular dynamics simulations

This paper presents a large-scale $ab$ $initio$ simulation study of amorphous silicon hydride ($a$-Si$_{\text{1-x}}$H$_{\text{x}}$) with an emphasis on the structure and properties of the material across a range of hydrogen concentration by combining accelerated molecular dynamics (MD) simulations with first-principles density-functional calculations. The accelerated MD scheme relied on classical metadynamics, which enabled the development of 2600+ high-quality structural models of $a$-Si$_{\text{1-x}}$H$_{\text{x}}$, with system sizes ranging from 150 to 6,000 atoms and hydrogen concentrations vary from 6 to 20 at. %H. The resulting amorphous networks were found to be completely free from any coordination defects and that they all exhibited a pristine band-gap in their electronic spectrum. The microstructural properties of hydrogen distributions were examined with great emphasis on the presence of isolated and clustered environments of hydrogen atoms. The results were compared with a suite of experimental data obtained from x-ray diffraction, infrared spectroscopy, spectroscopic ellipsometry and nuclear magnetic resonance studies.

cond-mat.mtrl-sci↗