Quadrant detector

Tyler, G.A., Pried, D.L., 1982, Image-position error associated with a quadrant detector, JOSA 72, 804... 

An area detector (MAR-CCD) with an active diameter of 130 mm is available. The use of an area detector has the advantage of having a better angular resolution than a quadrant detector, where the measurements have to be carried out by rotating the sample in the plane normal to the direction of the incident beam. Thus, two-dimensional scattering patterns can be obtained. 

Data were recorded using a quadrant detector a proportional gas chamber with delay line readout (Hendrix, Gabriel and Boulin, unpublished). 

The X-ray experiments were performed at the EMBL outstation at DESY, Hamburg, as described elsewhere [3-5], using instruments XI3 or X33 equipped with position sensitive detectors (linear or quadrant detectors for details see [8]. Assembly and disassembly were induced by temperature jumps between about 4 and 37 °C (half time 4 to 10 sec) [9]. Reciprocal spacings were calibrated with respect to the collagen reflections from a sample of cornea or tendon. The scattering curves were normalized with respect to the incident intensity measured by an ionization chamber just upstream from the specimen chamber. 

Together, these two assays opened up new avenues of research into actin and myosin interaction. Two different adaptations of the assay allow for the measurement of force by small numbers of myosin molecules (Kishino and Yanagida, 1988 Finer et al., 1994). The first of these uses a flexible, calibrated microneedle to which an actin filament is attached. The deflection of the needle as myosin moves the actin filament can be measured to determine the force (Kishino and Yanagida, 1988). In the second adaptation, an optical trap (Block, 1990) is used to measure both the force and step size of single myosin molecules (Finer etal., 1994). Beads are attached to each end of an actin filament. Dual optical traps position the beads (and thus the actin filament) in the vicinity of a single or a few myosin molecules. A sensitive quadrant detector is used to detect the position of the bead as myosin moves the actin filament. 

Simultaneous SAXS/WAXS measurements were made on beam line 8.2 of the SRS at the SERC Daresbury Laboratory, Warringtoiu UK. The details of the storage ring, radiation and camera geometry and data collection electronics have been given in det elsewhere [35]. The camera is equipped with a quadrant detector (SAXS) located 3.5 m from the sample position and a curved knife-edge detector (WAXS) that covers 120 of arc at a radius of 0.2 m. A vacuum chamber is placed between the sample and detectors in order to reduce air scattering and absorption. Both the exit window of the beam-line and the entrance window of the vacuum chamber are made from 15 un mica, the exit windows of the vacuum chambers are made from 15 pm mica and 10 pm Kapton film for the WAXS and SAXS detectors respectively. The WAXS detector has... 

Figure 3.23. Schematic of the four-quadrant detector used in optical lever detection AFM.

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