Performance of gas electron tracking detectors for beta decay studies

BRAND experiment electronics is using the charge to time conversion (QT) method for signal processing with constant time gate. The QT converts charge into time with linear response characteristics. For each event, a fixed gate width is used in which the charge from both ends of the wire is integrated. It is an innovative method involving a special conversion of the signal charge-to-time for all types of detectors used in the system. This allows synchronizing all detectors using only one digitizer type: CAEN V1190 MultiHit Time-to-Digital Converter (TDC). The new DAQ system was tested using a special simulator of the wire gas chamber signals. The wire itself is replaced by a potentiometer with the range reflecting the real wire resistance. The resistance of the signal wire is around 22 Ohm/cm. Therefore, a 2.2 kOhm resistor corresponding to a 1 m long wire was used in the simulator circuit. The tester utilizes two preamplifiers and signal cables connected to the selected channel. A simulator input is synchronized with a TTL signal triggering acquisition. The performance of the electronic circuit serving the charge division method was tested at different signal amplitudes.Figure shows a number of centroids the ADC pulse height asymmetry distributions acquired at different potentiometer asymmetry settings. The results were obtained for varying resistance division corresponding to the charge collected at both wire ends. The hit position corresponds to a unique potentiometer setting. The points zero correspond to the middle of the wire. The difference between the individual asymmetry spectra reflects the varying relation between the signal and noise amplitudes. The obtained ADC asymmetry is a monotonic function of the resistance asymmetry.Left panel describes: ADC pulse height asymmetry as a function of the resistance asymmetry. Right panel: standard deviation of the pulse height asymmetry in ADC unit as a function of the resistance asymmetry.