Thedevelopment of pink-beam 4D phase CT to observethelaser drilling into the poly(methyl methacrylate)

摘要

We report the development of pink-beam 4D (time-resolved) phase CT at BL28B2 at SPring-8 facility to observe fast phenomena related to the laser-induced drilling and engraving into the polymer. In our experimental configuration, the X-ray multilayer mirror was applied to filter out white synchrotron radiation and a resultant pink-beam with a mean energy of 25 keV and an energy bandwidth of 10 % was used for phase imaging by X-ray Talbot interferometer (XTI) . The main purpose of pink-beam was reduction of radiation damage caused to samples and tailoring the spectrum of X-ray beam fit to XTI. The XTI was composed of a π/2 phase grating (G1) and an amplitude grating (G2) with a pitch of 5.3 μm with a spacing corresponding to the 1st fractional Talbot distance of 283 mm between them. 4D phase CT was performed with the continuous fringe scanning technique to record a movie of differential phase images. In the continuous fringe scanning technique, during 5 continuous sample rotations, Gl was continuously moved by a distance equal to the grating pitch (5.3 μm). In this study, we improved the time for recording differential phase images during 180° sample rotation from previously reported 2 s to 1s. The improved temporal resolution was achieved by increasing of frame rate of X-ray detector from 1000 fps to 2000 fps while the number of projections per 180° rotation was maintained at a value of 400 and field of view was decreased from 1536 × 512 to 1024 × 512 (H × V). The developed pink-beam 4D phase CT set-up with improved temporal resolution was applied to observe laser-induced drilling into the poly (methyl methacrylate) (PMMA).