  A MicroCAT (Micro Compteur A Trous) structure which is used for avalanche
charge multiplication in gas filled radiation detectors has been optimised with
respect to maximum electron transparency and minimum ion feedback. We report on
the charge transfer behaviour and the achievable gas gain of this device. A
three-dimensional electron and ion transfer simulation is compared to results
derived from electric current measurements. Similarly, we present studies of
the charge transfer behaviour of a GEM (Gas Electron Multiplier) by current
measurements and simulations. Finally, we investigate the combination of the
MicroCAT and the GEM by measurements with respect to the performance at
different voltage settings, gas mixtures and gas pressures.
