Femtosecond laser based x-ray sources and their applications in phase contrast imaging

Atif Ali
The focus of this dissertation is to study the keV X-ray emission from different Z material to develop compact, quasi-continuous tabletop K α sources for the application of in-line phase contrast imaging, X-ray diffraction experiments and X-ray microscopy. The emission occurs from plasma produced by focusing 120 fs, 800 nm and 300 µJ Ti:Sapphire laser pulses up to an intensity of few times 10 16 W/cm 2 on Cu, Fe and Ag metal targets. The main interest of these experiments is to characterize the
more » ... fast electrons and X-ray emission from the laser plasma interaction. The investigation of X-ray emission energy and spectral characteristics is carried out by employing three detector systems which include filtered pin-diode, Charge Coupled Device and CdTe pulse height detectors. Scaling of photon flux as a function of incident laser energy is measured and related to the dynamics and absorption mechanisms involved in laser matter interaction. Specifically the construction and evaluation of K α X-ray sources operated at 1 kHz repetition rate is reported with a photon flux of ~ 7×10 9 photon/s, 3×10 9 photon/s and 1.4×10 7 photon/s around the K α line for Cu, Fe and Ag respectively. These K α fluences correspond to energy conversion efficiencies of around η Cu = 3×10 -5 , η Fe = 1.06×10 -5 and η Ag = 2×10 -7 . The Cu and Fe K α X-ray sources are applied to thin biological specimens and low atomic number (Z) materials to record in-line phase contrast images. It is demonstrated that the laser based K α sources can serve as alternative sources for conventional X-ray radiography of biological samples in clinical applications.
doi:10.7939/r3fs4b fatcat:qlr222lkwrc2ni4evojbycswyy