Focal Plane Assembly

Earth shield Primary mirror Focal plane assembly... 

FPA Focal Plane Array, Focal Plane Assembly... 

The largest change in this edition is the addition of three chapters describing modem detector assemblies and their operation in some detail. Chapter 6 deals with single detector assemblies and small arrays - used, for example, in motion detectors, intm-sion alarms, and fire sensors. Chapter 7 describes ROICs and focal plane assemblies (FPAs) - the core of modern imaging systems. Chapter 8 describes the electronics needed to operate and test ROICs and FPAs. 

At this time the NICMOS 3 design is complete, the flight qualification focal plane assemblies are in manufacture, and all flight focal planes are on schedule for delivery by the end of 1994. Identical focal plane arrays, not under flight qualification procedures, are in use in many observatories aroimd the world. The read out electronics systems differ and the observational modes differ between users. This has provided important information on the operation of the arrays under different circumstances and has inevitably led to different resrdts which depend on the method of use. The following describes the intended method of use for the NICMOS program. Any information from users utilizing the arrays in a similar way will be most welcome. 

The concentrator/spectrometer system consists of four separate concentrator mirror assemblies with a focal length of 185 cm, each one with a position sensitive. Xenon filled, GSPC in the focal plane, three covering the 1-10 keV range (ME), the fourth extending the range down to 0.1 keV (LE). 

Special mass spectrometry systems are built for isotope ratio measurements. Most isotope ratio mass spectrometers consist of a single-focusing magnetic sector instrument and a multiple Faraday cup detection system. Because the Faraday cup exhibits a stable response, it is an ideal detector for isotope ratio measurements. Simultaneous collection of relevant ion beams from all isotopes provides high-precision isotopic measurements. A three-Faraday cup detection system is shown in Figure 7.9. The multicup assembly is placed at the focal plane of the mass analyzer and can be used for the simultaneous detection of each isotopic form of the analyte species (e.g., m/z 44, 45, and 46 from CO2). Commercial instruments with up to nine collectors are available. 

When an electron beam passes through a specimen with ordered periodic structure, a diffraction pattern is formed on the back-focal plane of the objective lens. Electron diffraction is not only useful to generate images of diffraction contrast but also for structural analysis of supermolecules forming crystal or self-assembly. Electron diffraction pattern gives us information on the crystal structure, lattice repeat distance, and specimen shape. The pattern is always related to the image of the area of the specimen. Thus, there are basically three types of elecfion diffraction methods based on the size of the area of the specimen and the illumination modes of electron beam SAED, NEED, and convergent-beam electron diffraction (CBED). 

Experimental setups to study superheavy elements consist primarily of a recoil separator together with detector assemblies at the focal plane for discovery and decay experiments as well as surrounding the target position in case of in-beam studies. Detailed descriptions of each setup currently used in the world are available in the literature. Here we will focus on one example for a setup to explain the roles of the various detector systems in detail before summarising the properties of other widely used setups in a table. 

Some companies and workers refer to the ROIC detector array combination as a focal plane array (FPA). Others (including the author of this chapter) use the term SCA, reserving FPA for an assembly of SCAs together with a mechanical mounting structure and perhaps dedicated electronics. We have not enforced consistency in the text here. JDV... 

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