Detector operating temperature

Photon detectors must usually be cooled to achieve optimum performance the longer the cutoff wavelength, the lower must be the detector operating temperature T. There is a fundamental relationship between the temperature of the background viewed by the detector and the lower temperature at which the detector must operate to achieve BLIP performance [4.5]. At several places in this chapter we shall use as a quantitative example a photon detector operating at a temperature T=77K with a cutoff wavelength 12.4 pm one can scale... 

Related to the problem of detector operating temperature is that of its electrical power dissipation. A photoconductive detector must always carry a primary current / and therefore dissipate l R of electrical power, whereas a photovoltaic detector can be operated without a bias. The trend toward mechanical or electrical cooling, occurring for practical reasons, makes it necessary that a detector dissipate a minimum of electrical power and thereby heat itself as little as possible. 

Most of the applications of these detectors require detection of small signals at relatively high detector operating temperatures and in substantial back-... 

Both and increase with temperature approximately as Qxp - EJk T), so that (4.66) places an upper limit on the detector operating temperature. Using values of and from Appendix D and assuming a detector thickness t = 5 X lO cm as in Subsection 4.2.2 to give rj >0.9, we obtain the curve of the left side of (4.66) vs plotted in Fig. 4.10 for an operating temperature of 77 K. 

Our goal is to determine the possible approaches to optimize photon absorption and carrier transport in the active region of a semiconductor photonic infrared detector, and thus maximize specific detectivity. This should enable the elevation of the detector operating temperature and its operation as close to the room temperature as possible, all for a given spectral range and for a predefined set of technological parameters. 

Figure 5.2 Doped germanium and silicon detectors operating temperature, cutoff wavelength, and bandgap.

Since the photosensitive material and the electronics layer are very thin, the detector is mounted on a mechanical package for structural integrity. This package is thermally matched to the detector so that the detector will not be stretched or compressed during the large transition from room temperature to operating temperature. 

The apparatus employed for this study was a Waters Associates Model ALC/GPC 300 with a differential refractometer as mass detector operated at room temperature. A 2 ml sample loop with polymer concentrations of 0.01-0.1 wt.% cUid a 5 ml siphon were employed with mobile phase flowrates in the reuige 1-8 ml/min. 

Because of their high heat capacity, only few of the thermometers described in Chapter 9 can be used as sensors for detectors. Resistance (carbon) sensors were used for the first time in a cryogenic detector by Boyle and Rogers [12] in 1959. The carbon bolometer had a lot of advantages over the existing infrared detectors [13]. It was easy to build, inexpensive and of moderate heat capacity due to the low operating temperature. 

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