题　目：Advanced X-ray imaging and metrology with sandpaper
报告人：王洪昌（Diamond Light Source, UK）
时　间：6月26日（周五），下午1:30
地　点：物理馆512会议室

Abstract:

X-ray phase contrast imaging can substantially enhance the sensitivity for samples with weak absorption over the conventional absorption contrast imaging, whilst dark-field imaging techniques can provide supplemental and inaccessible information with sub-pixel resolution. Unlike the conventional absorption imaging, both phase and dark field contrast imaging can’t be measured directly. Most of existing imaging techniques are typically limited due to the requirement of either sophisticated experimental conditions or stringent beam properties. We have developed a novel imaging technique to extract both X-ray phase contrast and dark field imaging from speckle patterns created by sandpaper. The speckle based technique can be classified into single image mode and speckle scanning mode. The single image mode is highly desirable for rapid in-vivo radiography or computed tomography (CT) with moderate spatial resolution [1]. In contrast, the high resolution phase and dark-field signal can be extracted by scanning the sandpaper along single direction[2]. The new imaging technique is expected to open the way for X-ray multi-mode imaging for both biomedical applications and material science in the near future.

In addition, I will also briefly show you the recent development of in-situ and at-wavelength (i.e. using x-rays)metrology at Diamond [3,4]. Unprecedented angular sensitivity in single nanoradian has been achieved with speckle based technique [5,6]. The combination of at-wavelength and in-situ metrology method is considered the best pathway for surpassing the present optics performance and to realize the true nano-focusing optical elements needed for future synchrotron experiments.

References

1. H. Wang, S. Berujon, J. Herzen, et al, Sci. Rep. 5, 8762 (2015).
2. H. Wang, Y. Kashyap, and K. Sawhney, Phys. Rev. Lett. 114, 103901 (2015).
3. H. Wang, K. Sawhney, S. Berujon, et al, Opt. Lett. 39, 2518 (2014).
4. S. Berujon, H. Wang, S. Alcock, and K. Sawhney, Opt. Express 22, 6438 (2014).
5. H. Wang, J. Sutter, and K. Sawhney, Opt. Express 23, 1605 (2015).
6. H. Wang, K. Yogesh, L. David, and K. Sawhney, J. Synchrotron Rad. 22, (2015).

Brief Bio:

Hongchang Wang is a Senior Optics Scientist at Diamond Light Source. Since he received his Ph.D in Optics from Tongji University in 2007, he joined the Smart X-ray Optics consortium as a Post-Doctoral Research Fellow based at University College London where he developed a high angular resolution optic prototype for the next generation X-ray telescope. He moved on to the Diamond in 2009, and he is responsible for the optical design and commission for the soft x-ray beamlines. His research focuses soft X-ray polarimetry, in-situ metrology of X-ray optics and development of advanced X-ray imaging techniques.