Fig. 2: Determination of model parameters.

a Spectral intensities in pure-noise channels near m/q 907 illustrate sparsity of censored data. b Distribution of non-zero centroids across the whole spectrum compared with a Poisson distribution. c Variance and mean relationship for very low intensities. d Comparison of a simulated distribution of censored centroid data with the tails of the corresponding uncensored Rayleigh and hypothesized centroid distributions. e Distributions of the 50 and 200 pA data within 50-kHz windows in the low-signal regime and f Squared means of the distributions shown in panel e plotted against the square root of m/q with line fits to estimate the detector-noise variance components. The integral average of the noise is indicated in the figure.