A Composite Velocity Map Imaging Spectrometer for Ions and 1 keV Electrons at the Shanghai Soft X-ray Free-Electron Laser

Velocity map imaging (VMI) spectrometry is widely used to measure the momentum distribution of charged particles with kinetic energy a few tens electronVolts. With progress femtosecond laser and X-ray free-electron laser, it becomes increasingly important extend electron 1 keV. Here, we report on recently built composite VMI spectrometer at Shanghai soft which can ion images high-energy simultaneously. In SIMION simulation, extended keV resolution <2% while measuring ions 20 eV. The experimental performance tested by Ar 2p photoelectron spectra Synchrotron Radiation Facility, O+ spectrum from dissociative ionization O2 800 nm laser. We reached 1.5% 500 When arm set for 100 eV, 4% 5.6 This will support experiment, such as multi-photon excitation/ionization, Auger electrons emission, attosecond streaking.