In this article we present some basic considerations in the design of a time detector for high energy (0.2–1.0 MeV) particle detection. Based on these considerations, a novel time detector design is proposed in order to overcome some of the problems in existing designs. Improvement in the timing resolution(<50 ps)and efficiency(>70&percent;for 4.0 MeV &agr; particles) is expected and a compact detector structure with ultrahigh vacuum compatibility is achieved. The new design employs a novel form of crossed electric and magnetic fields to deflect the electrons emitted from a thin foil to form a timing signal. In this design electrons are transported in a grid-free region and the energetic particle needs to pass through the grid once only. The electric field was produced by three metal plates forming a triangular prism. The magnetic field was generated by a coil pair which creates a uniform field in the electron transport region. Computer simulation and numerical analysis were performed to calculate the electric and magnetic field as well as the electron trajectory and flight time. The detector timing resolution is analyzed and the spread in electron initial energy contributes a significant portion. To avoid the complicated numerical details in field and trajectory calculations, we use an empirical approach in this article to illustrate the design principle. Some experimental results are presented to compare with the calculations. ©1997 American Institute of Physics.