Speaker
Description
Two 50 cm long protype sMDT drift tubes have been irradiated using
beta-electrons from ^{90}Sr-^{90}Y decays with end point energy of 2.28 MeV.
Over two periods of 100 days and 125 days, respectively, the tubes were drawing
constant currents of 3 uA and 1.25 uA. Regions of approximately 10 cm of
the wires were irradiated intensively. Almost 40 C of charges have
been accumulated in these regions on each wire.
As detector gas Ar:CO2 93:7 Vol-% was used at 3 bar absolute,
the anode voltage of 2730 V was extremely stable over the whole period.
Pressure and temperature were monitored together with anode-voltage and
amplification-current in the drift-tube.
We report on the experimental method and the setup and conclude from
the observation of constant current over the whole period that no
reduction in performance has been observed and thus no sign of long-term deterioration.