High Energy Photoemission: Development of a New Electrostatic Lens for a Novel High Resolution Spectrometer

In recent years growing interest has been dedicated to photoemission experiments at high energy because a significant bulk sensitivity in photoemission measurements can be achieved only by increasing the kinetic energy of the analysed photoelectrons. Within the 5th European framework, a RTD project named VOLPE (VOLume PhotoEmission from solids) has been funded. Aim of the project is to measure bulk electronic properties on solids by the Photoemission Spectroscopy with Synchrotron Radiation preserving an energy resolution comparable to modern surface sensitive photoemission spectra. This will be possible by performing photoemission experiments in a photolectron Kinetic Energy range of 6-10 keV, keeping the overall energy resolution at 20-30 meV. Presently, the beamline ID16 at ESRF posses the necessary characteristics (1011 photons/sec and 15-100 meV resolution at photon energies between 6 keV and 15 keV) to perform these class of experiments, while a new spectrometer is being developed in the framework of VOLPE project. This spectrometer is an hemispherical deflector analyser with electrostatic input lens and 2D position sensitive detector. The spectrometer will be characterised by an ultimate resolving power of 3 105 @ 10 keV. We will report on the particular lens system developed for this project which is optimised to guarantee very high retarding ratio, between 50 and 600, with constant linear magnification. A prototype of this lens has been realised and we will report on the first measurements performed at INFM, Unità Roma Tre.