Single Element Detector Assemblies

Figure 4.11 MCA spectra from a single element of a Ge array detector showing the effects of including a Zr filter and Soller slit assembly. For the without filter data, the intensity of the incident beam was attenuated by approximately a factor of 20 by inserting an aluminum metal absorber into the upstream beam in order to maintain the detector at a non-saturating count-rate. The sample was an aqueous solution of human sulfite oxidase (0.2 mM Mo, 20 mM PIPES pH 7.0). The incident X-ray energy was 20900 eV, equivalent to the elastic scatter energy.

The 2D x-ray systems are very effective in testing single-sided assemblies. With the use of a sample manipulator, an oblique view angle enhances inspection of both single- and doublesided assemblies with some loss of magnification due to increase in distance between source and detector. Experience is needed in discerning between bottom-side board elements and actual solder and component defects. This can be very difficult or impossible on extremely dense assemblies. As discussed previously, certain solder-related defects such as voids, misalignments, solder shorts, etc. are easily identified by transmission systems. However, even an experienced operator can miss other anomalies such as insufficient solder, apparent open connections, and cold solder joints. 

The other configuration is discussed in this chapter it includes single detectors and arrays of a few elements - often 1,2, or 4, or perhaps as many as 16 or even 64. These often include special-purpose electronics. We will discuss those in this chapter. For brevity, we will refer to these as single detector assemblies - with the understanding that they may include more than one element. Figures 6.1 and 6.2 show a single element and a four-pixel, four-color mini-array in TO-5 packages the electronics are mounted separately. 

Testing of infrared detectors is discussed in Chapter 10. Much of that material applies to single detector assemblies as well as FPAs. Table 6.3 highlights the general differences between testing of single detector assemblies and testing of FPAs. The extent of automation, of course, depends on the required production rates and the number of elements in each unit. 

Interactions between the HIV-1 regulatory protein. Rev, and the Rev responsive element (RRE) RNA, as well as the effect of inhibitors on these interactions, were monitored using a single-particle fluorescence-based method [203]. This biosensing method combined FRET and the colocalization of fluorophores as the means of detection. In the presence of an analyte, the dye-labeled recognition complex was assembled on the fluorescent QDs, and these were tunneled, under flow, into two detector channels that simultaneously analyzed the fluorescence of the QDs and the FRET emission of the dye. The two emissions were observed simultaneously only if... 

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