Some may have been wondering what I have been up to lately!
Since the beginning of the year, I started working on the ALS-U project, which is the upgrade of the Advanced Light Source, the main synchrotron at Lawrence Berkeley National Laboratory. The goal is to improve the facility with a Diffraction-Limited Storage Ring (DLSR), in order to increase the brilliance of the beam, so as allow scientists from all over the world to perform the most precise experiments, allowing bright and full coherent beams with diameters as small as 10 nanometer, or twice the width of a strand of DNA. (here’s a report on all the niceties you can do with such a tool: ALS-U: Solving Scientific Challenges with Coherent Soft X-Rays)
At the same time, the first mirror in the beam will have to withstand heatloads in the tens of kilowatts.Even with the best efforts in cooling designs, monitoring the aberrations for active correction of the beam is likely to be required, and that’s part of what I’m working on, as part of the Wavefront Preserving Mirror project, a joint project between APS, NSLS-II, LCLS and the ALS.
Soft X-Ray is important because it allows chemical specificity since it corresponds to the K-edge (i.e. the energy needed to ionize electrons from the inner electron shell of atoms) of many atoms. The problem is of course the these radiations get very strongly absorbed, and thus are very difficult to produce. [Here is a list of all the cool things this is meant to allow – science opportunity]There is a global push in the world for generation IV light sources, which are divided between DLSR synchrotrons and Free-Electron Lasers. Among synchrtrons, the first (and only) Gen IV light source is MaxIV in Sweden, operated by Lund university. Other light sources around the world are staged for an upgrade, like SLS-II in Switzerland or Soleil in France.
Free-Electron Lasers constitute the other part of GenIV (There are few in the world, such as LCLS at SLAC/Stanford, Fermi (at Elettra) in Italy, SACLA in Japan, and the brand new SwissFEL and European XFEL in Hamburg.) FELs are exciting for they produce intense (1~0GW) flashes of light (~10fs) allow the study of very small time-scale phenomenon. A lot of very interesting phenomena can be studied that way, the drawback is that oftentimes samples get destoyed by the measurement, and that only one experiment can be carried out at a time. Synchrotrons are somehow more versatile (they can host over 40 experiments at the same time.)