| Autor: |
Goldie, D. J., Audley, M. D., Glowacka, D. M., Tsaneva, V. N., Withington, S. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; Apr2009, Vol. 105 Issue 7, p074512-074512-7, 7p, 1 Color Photograph, 3 Diagrams, 1 Chart, 4 Graphs |
| Abstrakt: |
Detectors based on transition edge sensors (TESs) must achieve theoretically predicted noise levels if they are to be suitable for the next generation of space-borne astronomical telescopes. The noise of an ideal detector is determined by the sum of three contributions: (i) thermal-fluctuation noise in the heat link to the bath, (ii) Johnson noise in the sensor itself, and (iii) noise in the electrical read-out circuit. Many groups have reported TESs with noise levels significantly above the theoretical predictions. We use two well-defined experimental configurations to measure the read-out noise spectra of Mo–Cu TESs with transition temperatures of 370 and 200 mK. The TESs are geometrically simple, comprising superconducting and normal metal films on a silicon nitride (SiNx) membrane. The measurements are compared with a multiparameter noise model, which is based on a physical model of the thin-film devices. Taking into consideration separate, accurate measurements of the heat capacity of identical SiNx membranes, we are able to provide a good account of both the magnitude and frequency dependences of the measured current-noise spectra. We find that an important excess noise mechanism involves the random exchange of heat between the heat capacity of the bilayer and the heat capacity of the nitride membrane, with either the thermal conductance of the membrane, or in some cases the thermal conductance of the bilayer, being the mediating path. Clear design recommendations are given to achieve the best possible noise performance. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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