A compact design for velocity-map imaging of energetic electrons and ions

Abstract

We present a compact design for a velocity-map imaging spectrometer for energetic electrons and ions. The standard geometry by Eppink and Parker [Rev. Sci. Instrum. 68, 3477 (1997)] is augmented by just two extended electrodes so as to realize an additional einzel lens. In this way, for a maximum electrode voltage of 7 kV, we experimentally demonstrate imaging of electrons with energies up to 65 eV. Simulations show that energy acceptances ≲270 and ≲1200 eV with an energy resolution ΔE∕E≲5% are achievable for electrode voltages ≤20 kV when using diameters of the position-sensitive detector of 42 and 78 mm, respectively.

Ignition of a helium nanoplasma by x-ray multiple ionization of a heavy rare-gas core

“…The experiments were performed at the XUV-FEL facility FLASH at DESY in Hamburg. A continuous He nanodroplet apparatus including a gas doping unit and a combined electron velocity-map imaging and ion time-offlight mass spectrometer [21] was mounted at the openport beamline BL2. The focused soft x-ray (5 nm) and NIR (800 nm) beams were collinearly superimposed using a mirror with a centered hole mounted at the exit of the beamline.…”

Single-shot electron imaging of dopant-induced nanoplasmas

“…Assuming that the VMI technique is in principle applicable to imaging of nanoplasma electrons, we can convert the measured radial intensity profile into an electron kinetic energy distribution according to electron-trajectory simulations validated by calibration measurements [33]. Fig.…”

“…The main novelty is the implementation of a combined VMI and TOF detector, capable of detecting energetic electrons and ions, see Fig. 1, [33]. The He nanodroplets, respectively Ne clusters, were produced by a supersonic expansion at high stagnation pressure (p 0 = 20-50, 10 bar) and low temperature (T 0 = 9-15 K, 37-41 K) through a thin-walled nozzle with a diameter of 5 µm for He and 20 µm for Ne.…”

“…The detector consists of a compact VMI spectrometer capable of detecting high-energy electrons [33], and a TOF ion spectrometer placed on the opposite side which is based on a Daly type detector [38], see Fig. 1.…”

Multichromatic Polarization-Controlled Pulse Sequences for Coherent Control of Multiphoton Ionization

“…The use of advanced polarization-shaped pulses for the generation of free electron wave packets by MPI has necessitated 3D detection to characterize the full 3D photoelectron momentum distribution (PMD). While time-offlight techniques enabled the kinetic energy-resolved detection of photoelectrons from ultrafast MPI dynamics [81,82], their angular distribution became available through the use of velocity map imaging (VMI) techniques [83][84][85]. Currently, the most sophisticated detection method is based on COLTRIMS [86,87].…”