Performance studies of an ultrafast gamma Cherenkov imaging Screen based on Silica fibers array.

High-energy gamma rays produced in inertial confinement fusion (ICF) experiments are crucial for studying implosion dynamics. These gamma rays, characterized by their extremely short durations, represent the least disturbed products of fusion, preserving vital birth information. To detect such γ-rays, ultrafast radiation detectors with high time resolution are necessary. This study introduces a newly developed Cherenkov optical image screen designed for ultra-fast gamma-ray imaging. Composed of pure quartz fiber material, the imaging screen features a single fiber pixel size of 0.6 mm and a thickness of 3 cm. Theoretical investigations explore the luminous time response and efficiency of the Cherenkov optical imaging screen under gamma-ray irradiation. Experimental validation was conducted using a steady-state gamma-ray source with an average energy of 1.25 MeV. Results demonstrate that the image screen achieves a spatial resolution limit of 0.75 mm. The temporal response exhibits a full width at half maximum of less than 0.4 ns when excited by a high-energy electron beam with a single pulse duration of several picoseconds.

Two-dimensional monitoring of a laser-solid x-ray source spot via penumbral coded aperture imaging technique.

The uncertainties of spot size and position need to be clarified for x-ray sources as they can affect the detecting precision of the x-ray probe beam in applications such as radiography. In particular, for laser-driven x-ray sources, they would be more significant as they influence the inevitable fluctuation of the driving laser pulses. Here, we have employed the penumberal coded aperture imaging technique to diagnose the two-dimensional spatial distribution of an x-ray emission source spot generated from a Cu solid target irradiated by an intense laser pulse. Taking advantage of the high detection efficiency and high spatial resolution of this technique, the x-ray source spot is characterized with a relative error of ∼5% in the full width at half maximum of the intensity profile in a single-shot mode for general laser parameters, which makes it possible to reveal the information of the unfixed spot size and position precisely. Our results show the necessity and feasibility of monitoring the spot of these novel laser-driven x-ray sources via the penumbral coded aperture imaging technique.