Abstract Details
High contrast femtosecond laser-driven intense keV x-ray sources
Author: Liming Chen
Requested Type: Oral Only
Submitted: 2009-04-21 01:48:43
Co-authors:
Contact Info:
Institute of Physics, Chinese academy of Sciences
8 NanSanJie, ZongGuangCun
Beijing, Beijing 100190
China
Abstract Text:
Hard x-ray emission from femtosecond laser produced plasmas has been studied in the past years. Such hard x-ray sources have a number of interesting applications in the dynamic probing of matter and in medical imaging. However, the hard x-ray emission produced by high intensity laser-solid interactions relies on hot electrons. Unfortunately, typically the x-ray continuum in spectrum is strong and usually contains 90% of total x-ray energy with photon energies > 1 keV [1]. In the worst case, the small energetic x-ray tail will greatly reduce the subject contrast of in-line radiography. This is a disadvantage for laser-based x-ray sources in imaging applications.
We present the result of hard x-ray spectroscopy from an Ar gas+cluster target irradiated by a femtosecond laser pulse at 10^17 W/cm2 [2]. The spectrum shows a high contrast characteristic K-shell emission, a compressed continuum and the elimination of the energetic x-ray tail typically observed with solid target. This Ar K-shell x-ray with very little continuum background possesses the measured flux of 1.2 x 10^3 photons/mrad^2/pulse. The peak brightness is estimated to be ~1.2 x 10^21 photons/s/mm^2/mrad^2, which is comparable to the third generation synchrotron radiation sources. this source is critically depends as a function on the contrast of laser pulse. This compact quasi-monochromatic x-ray source, with a source size of only 12 µm, has been applied to x-ray radiographic imaging of a biological specimen, resulting in high-resolution phase-contrast images. Correlation between this intense K-shell emission with the laser channeling in the Ar gas is addressed. Recently, tenfold of x-ray enhancement is obtained [3] which ascribe to the new electron heating mechanism. For the first time, single-shot keV photon phase-contrast-imaging is available now which is suit for the ultrafast x-ray radiography.
1. J. Yu et al, Phys. Plasmas 6, 1318 (1999)
2. L. M. Chen et al, Appl. Phys. Lett. 90, 211501(2007)
3. L. M. Chen et al, to be submitted
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