case of missing hydrogen atoms.\
To overcome this problem, a new spectrometer was designed using SIMION to simulate the electron and ion trajectories. On the ion side, a higher electric field and a long homogeneous field region, together with an electrostatic lense, proved to best fulfill the requirements. An additional field-free drift region was added in front of the ion detector, resembling a spectrometer design which is (employing low electric fields) typically used for investigation of atomic targets. This field design led to a significant improvement in the fragment identification of methyloxirane [@Tia2016].\
An additional benefit of this design is the fact that the ions are accelerated to an energy of around 2000 eV, at which the efficiency of the microchannel-plate detectors already reaches reasonable values. This allows to omit the electrostatic meshes that are usually added in front of the detector to provide a short post-acceleration region with high electric field. As the typical transmission of the employed meshes is 0.78, they lead to a reduction in efficiency by a factor of 2.7 when attempting to measure four particles in coincidence.\
The electron side of the spectrometer consisted simply of a homogeneous field. The high field that was determined 