Schematic representation of the DROID geometry with a top and side view, the thickness of the layers is greatly exaggerated.
Different groups of quasiparticles in a DROID which are determined by position in the DROID (horizontal scale) and energy (vertical scale).
Scatter plot of the sum vs normalized ratio of the result from the simulated shaping stages. Events from the STJs can be easily distinguished and selected by their spatial separation. The absorber events are divided into 11 sections along the position direction.
The fit of the model to the measured charge output of the three DROID geometries. Each graph shows the charge output of the two STJs vs normalized charge ratio, (asterisk for , plus sign for ), with the fit of the model over plotted, solid lines. The dashed line is the calculated from the fit results. All measurements are from an illumination with 5 eV photons at an operating temperature of 295 mK. (a) Shows the responsivity of the DROID with 30 nm aluminum trapping layers at . (b) Shows a measurement from the same device with the same settings but biased at a voltage of for direct comparison with the other devices, and [(c) and (d)] show measurements for the DROIDs with 60 and 100 nm aluminum trapping layers, respectively.
Fitted values for the fraction of quasiparticles above as a function of bias voltage for the DROIDs with 30 nm (diamonds), 60 nm (triangles), and 100 nm (squares) aluminum trapping layers. The filled symbols are for the left STJ and the open symbols are for the right STJ.
Diffusion constant vs temperature for the DROID with 30 nm aluminum trapping layers. The different symbols denote the diffusion constant in the absorber (crosses), left STJ (open diamonds), and right STJ (filled diamonds). The solid line denotes the theoretical diffusion constant as predicted by Eq. (22).
DOS of the BCS tantalum absorber (solid line) and Ta/Al STJ (dashed line).
Loss rates in the DROIDs with different lengths from 30 nm Al series. The loss rate in the absorber (crosses) is constant indicating homogeneous tantalum layer quality. The loss rate in the STJs (diamonds, open: left and filled: right) shows scatter between the DROIDs. This is caused by differences in plug quality.
Values of the fixed parameters. The values are calculated separately using different models.
The average parameters resulting from the fit of the model to the experimental data obtained with the reference device at and , for 60 and 100 nm Al layer, and , for 30 nm Al layer.
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