A Microdot (MDOT) detector has been overcoated with a boron-doped amorphous silicon carbide semiconductive layer. The stable operation of the device in mixtures of argon, neon and helium with di methyl ether (DME) at high gains and at high counting rates is shown. Radiation damage tests give a lifetime of over 120 mC/cm using a gas system with plastic gas pipes. (C) 1998 Elsevier Science B.V. All rights reserved.