Performance benchmark of a gateable microchannel plate detector for extreme ultraviolet radiation with high temporal resolution

摘要

Research in ultrafast nanoscale phenomena requires high spatial and temporal resolution detectors. Optical imaging microscopes achieve high time resolution but low spatial resolution and scanning microscopes vice versa. Extreme ultraviolet imaging microscopy closes this gap but demands a suited two dimensional detector for efficient use of photons and simultaneously enabling fast gating. We use a micro-channel plate photoelectron multiplier together with a phosphor screen as a detector. We pulse the operation voltage of the electron-multiplier for 1.25 ns. Only during that time the detector is highly sensitive to extreme ultraviolet light. A custom built impedance-transformer delivers high currents into the plates' capacitance. This leads to a short charging time and ensures a narrow temporal sensitivity window. We analyzed the following attributes of the detector system: - Temporal behavior is measured by femtosecond illumination with high harmonics generation radiation at different relative delays. The sensitivity curve has a width of 2 ns. Electronic timing jitter is below 150 ps. - Spatial resolution is determined by mapping the shadow of a sharp edge on the detector. The smearing gives information about the modulation transfer function. The resolution limit according to the Rayleigh criterion is at 12 lp/mm or a minimum resolvable pitch of 80 μm. - Spectral sensitivity of the detector is calibrated for extreme ultraviolet wavelengths ranging from 1 nm to 30 nm at the PTB facility at the BESSY2 synchrotron. In summary the detector provides a spatial resolution down to 80 nm and a time resolution shorter than 2 ns using a discharge produced plasma EUV source and a zone plate based microscope with a magnification of ~ 1000x. This is a highly interesting combination and will help to investigate a variety of short time processes in nanoscience.