Thursday, December 3rd , 2020
3:45 – 4:45 p.m.
WEBEX
 
  
Speaker: Prof. William S. Graves
Arizona State University
https://biodesign.asu.edu/william-graves
 
“Toward completely coherent x-ray lasers”
 
 
 
Abstract: 
 
X-ray science is moving beyond static images of molecular structure toward time/energy dynamics that track, for instance, transient states in the catalytic cycle, charge transfer in chemical reactions, subtle energy shifts in correlated electron systems, and the function of conformal changes in protein structures, all while resolving atomic spatial scales.  A novel x-ray free-electron laser (XFEL) is under development at ASU that promises to produce fully coherent x-rays for studies that resolve molecular spatial scales and atomic excitations at the fastest electronic timescales.  Furthermore, the instrument is of a size and cost appropriate to a university rather than today’s kilometer-scale XFELs.  The compact XFEL (CXFEL) depends on a novel method of diffracting electrons that then produce a coherent laser-like x-ray beam that is transform-limited in all dimensions, i.e., with all photons in a single quantum state.  The method allows for coherent control of the phase, frequency, bandwidth, pulse length and amplitude of the x-ray pulses, and enables a variety of multi-color pump-probe experiments with precisely tunable attosecond to femtosecond delays for experiments. 
In this talk I will present the status of the Compact X-ray Light Source (CXLS) that is the first phase of the CXFEL.  CXLS is a femtosecond x-ray source but not yet a laser.  I will then present the current design of CXFEL and a survey of its x-ray applications in ultrafast atomic dynamics, properties of quantum materials, and time-resolved biochemistry.