Noise measured on collection plane wires as a function of time. Each data point corresponds to
the measured noise level for a given run. The times shown are the times at which each run was taken. For each run, a list of channels was selected such that 1) it was a collection plane wire, 2) it had noise values within a certain range. The average and standard deviation of the distribution of RMS noise values for channels passing the cut was calculated. Data points represent the average RMS, and error-bars show the standard deviation of these distributions. Error bars are meant to show how the change in temperature affects noise levels compared to the intrinsic variability of noise in the detector due to channel-to-channel gain variations.
ENC values are measured in number of electrons by taking the ADC noise measured at a 14 mV/fC ASIC gain and multiplying it by [ 1.6E-4 (fC/e-) X 1.935 (ADC/mV) X 14 (mV/fC)]^-1.
Noise values drop with the gasseous argon temperature. This is expected behavior due mainly to the properties of the CMOS ASIC chips.
The red vertical line in this plot represents the time at which the LAr filling-process began. After this point noise levels begin to rise. This behavior is explained in the Tech-Note in DocDB 4717 in Sec. 5.
Sporadicity of the data-points is due to irregular run-taking patterns in the very early weeks of the commissioning phase.
Noise levels fluctuate slightly upwards in early and mid June. This is because the cryostat cooling was temporarily interrupted for a brief period, allowing the temperature, and thus the noise values, to rise.