2019 Physics/Theoretical Colloquium

 

Thursday, March 14th , 2019

3:45 – 4:45 p.m.

Rosen Auditorium (TA-53, Bldg. 1)

Refreshments at 3:15pm

 

Speaker:  Prof. Alessandro Olivo  and Dr. Marco Endrizzi

 

Dept. of Medical Physics & Biomedical Engineering

University College London

 

 

“Origins, state-of-the-art and prospective applications of intensity-modulation based incoherent phase imaging "

 

 

 

Abstract: 

Over recent years, it has been repeatedly proven that the exploitation of phase effects can radically transform the effectiveness and range of applications of x-ray imaging. By means of phase-based techniques, features that have been traditionally considered x-ray invisible become detectable, and the visibility of all details in an image is enhanced. Moreover, a type of phase-based x-ray imaging referred to as dark-field (or ultra-small-angle x-ray scattering) imaging enables the detection of features well below the resolution limit of the imaging system, simultaneously giving access to additional and complementary information on the imaged sample.

 

Phase effects are traditionally considered to require high spatial coherence, a feature which is readily available at synchrotrons but which in a traditional lab depends upon the use of either micron-size focuses or strong collimation/aperturing. This limits the available x-ray flux and can increase the setup complexity.

 

At UCL we have followed a different strategy based on strongly structuring the incoming x-ray beam using masks in which apertures are carved in strongly (ideally fully) absorbing substrates. We have shown that this is a versatile, flexible approach that enables to significantly relax the coherence requirements and to use relatively large (e.g. 100 mm) focal spot size with no collimation or aperturing; despite this, phase and dark field signal can be quantitatively retrieved in a variety of ways.

 

Over the last 10 years, we have developed large area and microscopic implementations, both in 2D and 3D (i.e. computed tomography), and demonstrated significant advantages in a range of applications including medicine, biology, security, NDT and material science.