Soft Report - Dipartimento di Fisica - Sapienza

Soft Resonant X-ray Scattering (RIXS) from solids:Results on InstrumentationA X Em d va nc ed -Ra y issio n Sp ec tro sc op ySAXES& Swiss Lig ht So urc ePolitecnico di Milanoallowing to scan the scattering cross section at allangles. The second instrument is less versatile interms of angular scan but is much more effective inthe selection of the energy window because it isbased on a multilayer system. In this case it is alsopossible to carry out the polarization analysis of thescattered radiation.It is in the scientific tradition of the AXES group todevelop new instrumentation at the forefront of theinternational standard. This implies a continuousupgrading of the existing instruments and the designand development of new machines. In thisconnection the main achievements are the following.1. Equipment for RIXS measurements at the ESRF(ID08 beamline)This is the instrument used at the ESRF to takespectra with resolution both in the incident and inthe scattered photon beam. The instrument entirelydeveloped at the Politecnico di Milano and fullysupported by INFM/CNR consists of amonochromator used to prepare the incident beam(this instrument is called Polifemo) and in aspectrograph used to measure the scattered photonenergy past the sample (this instrument is calledAXES). The first spectra from AXES came out in 1994with white beam excitation and Polifemo wasinstalled in 1997. Due to continuous upgrading onlythe mechanical setup remains essentially the same.A part of the optics has been changed and thedetector (a CCD ) is completely new. Thanks to theseimprovements the system has top levelperformances at the international level among theinstruments operated routinely in the range from450 eV to about 1300 eV. The typical resolvingpower around 600 eV is 2000 (note that this is thecombined resolving power including both Polifemoand AXES).3. Equipment for RIXS measurements at the SwissLight Source (ADRESS beamline)This instrument is property of the Paul ScherrerInsitut (PSI, Villigen, Switzerland) and has beendesigned and built at the Politecnico di Milano. Itexploits the expertise accumulate by our group in the10 years of the AXES project and is conceived toreach even better performances. For this reason theinstrument is called SAXES (Super-AXES). It isdesigned to have a resolving power around 8000-10000 and it will be mounted on a rotating opticalbench in order to do measurements as a function ofthe transferred momentum. The better energyresolution is obtained at the price of a lowerefficiency in SAXES than in AXES: the twospectrometers are complementary and they will beboth kept operational in the future. SAXES shouldbecome operational at the ADRESS beam line of theSwiss Light Source at the beginning of 2007. Thefirst tests on energy resolution made withconventional x-ray sources in Milano have shownthat the target performances have been reached.SAMPLEAREA INCLUDED INTHE SPECTROMETERACCEPTANCEILLUMINATEDSURFACEINCIDENTBEAM2D POSITIONSENSITIVEDETECTOREMITTEDPHOTONSSPECTROMETERENTRANCE SLIT SPECTROMETERGRATING2. Equipments for Integrated Raman (IRRS)measurements at the ESRF (ID08 beamline)We have developed two instruments to exploit thisnew experimental approach. The first instrumentselects the scattering channel with absorption filtersinstalled on a goniometer in ultra high vacuumPartecipantsL.Braicovich, C.Dallera, G.Ghringhelli, A.Tagliaferri,A. Piazzalunga, F. Fracassi, INFM-CNR and Dip. diFisica, Politecnico di Milano, Italy.101SOFT Scientific Report 2004-06