Thick-lens velocity-map imaging spectrometer with high resolution for high-energy charged particles

Abstract

A novel design for a velocity-map imaging (VMI) spectrometer with high resolution over a wide energy range surpassing a standard VMI design is reported. The main difference to a standard three-electrode VMI is the spatial extension of the applied field using 11 electrodes forming a thick-lens. This permits measurements of charged particles with higher energies while achieving excellent resolving power over a wide range of energies. Using SIMION simulations, the thick-lens VMI is compared to a standard design for up to 360 eV electrons. The simulations also show that the new spectrometer design is suited for charged-particle detection with up to 1 keV using a repeller-electrode voltage of-30 kV. The experimental performance is tested by laserinduced ionization of rare gases producing electrons up to about 70 eV. The thick-lens VMI is useful for a wide variety of studies on atoms, molecules and nanoparticles in intense laser fields and highphoton-energy fields from high-harmonic-generation or free-electron lasers.

The importance of Rydberg orbitals in dissociative ionization of small hydrocarbon molecules in intense laser fields

“…Our VMI spectrometer follows well-documented design and operation, e.g., 79 , 95 . An effusive gas jet of the target hydrocarbon molecules intersects the laser beam inside the spectrometer, which is composed of an electrostatic lens system that focuses photofragments to specific radii on the detector depending upon their transverse momenta.…”

Incorporating real time velocity map image reconstruction into closed-loop coherent control

“…Pulse shapes are monitored with a Second-Harmonic-Generation FrequencyResolved Optical Gating (SHG FROG) 28 scheme. The thick-lens VMI spectrometer used in these experiments has been described in other publications [29][30][31] and contains an effusive jet to deliver the target gas, similar to the one described by Ghafur and co-workers. 32 As shown in Fig.…”

Single-shot temporal characterization of ultrashort XUV pulses

“…The 11 electrode assembly was mounted in "thick lens" configuration. 9 in order to maintain a good energy resolution over a broad kinetic energy range (⇠ 0 -100 eV in our case). The VMI was designed using a trajectory simulation of charged particles with the SIMION software.…”