The experiment made on October 11th is an absorption spectroscopy experiment in the X ray range (EXAFS, Extended X ray Absorption Fine Structure): a sample – a cupper sheet 7 µm thin – receives the high energy photons coming from the optic hutch. The monochromator installed in that hutch selects the photons of a chosen wavelength from the white beam produced in the storage ring. Thanks to photon detectors located before and after the sample, one can measure the quantity of photons absorbed by the cupper. A series of measurements is made with di ff erent wavelengths, and thus energies, of the incident photons. It is called an energy scanning (here: from 8700 to 9700 eV).
An absorption spectrum is obtained (figure 1), which is a real “signature” of the studied element. The persons who are familiar with synchrotron radiation will notice that this spectrum is a proof of a high quality beam. It augurs well for the following steps of the beamline installation. The main peak, called absorption threshold, around 8980 eV, is characteristic of Cu.It is followed by several smaller peaks that give information on the interatomic distances in the sample. This spectrum is exactly as expected for this reference sample and, furthermore, already gives a very good resolution of the peaks.
Figure 1
The DiffAbs team will now keep working on the improvement of the spectra resolution, with the satisfaction of these first results. A turning point has just been passed!
