A new ion-ion coincidence imaging spectrometer based on a pixelated
complementary metal-oxide-semiconductor detector has been developed for the
investigation of molecular ionization and fragmentation processes in strong
laser fields. Used as a part of a velocity map imaging spectrometer, the
detection system is comprised of a set of microchannel plates and a Timepix
detector. A fast time-to-digital converter (TDC) is used to enhance the ion
time-of-flight resolution by correlating timestamps registered separately by
the Timepix detector and the TDC. In addition, sub-pixel spatial resolution
(<6 μm) is achieved by the use of a center-of-mass centroiding algorithm. This
performance is achieved while retaining a high event rate (104 per s). The
spectrometer was characterized and used in a proof-of-principle experiment on
strong field dissociative double ionization of carbon dioxide molecules (CO2),
using a 400 kHz repetition rate laser system. The experimental results
demonstrate that the spectrometer can detect multiple ions in coincidence,
making it a valuable tool for studying the fragmentation dynamics of molecules
in strong laser fields