X-ray transducers

To tthtain convenient counting rates, the output from an X-ray transducer is sometimes scaled —that is, the number of pulses is reduced by dividing by some mui-tiple of ten or two, depending on whether the circuit is a decade or a binary device. A brief description of electronic scalers is found in Section 4C-4. Counting of the scaled pulses is carried out with electronic counters such as those described in Sections 4C-2 and 4C-3. 

And a rotation of the emitter-receiver transducer around the "object" (or a rotation of the object) gives a annulus of center O and radii [Km, Km] [2]. The situation is identical to that of X-ray tomography (slice-by-slice spectral coverage), but with a band-pass spectral filter instead of a low-pass spectral filter. ... 

Adjustable Workbench (PAW) instrument assembly. The SH shown in Figs. 3.15 and 3.16 contains the electromechanical transducer (mounted in the center), the main and reference Co/Rh sources, multilayered radiation shields, detectors and their preamplifiers and main (linear) amplifiers, and a contact plate and sensor. The contact plate and contact sensor are used in conjunction with the IDD to apply a small preload when it places the SH holding it firmly against the target. The electronics board contains power supplies/conditioners, the dedicated CPU, different kinds of memory, firmware, and associated circuitry for instrument control and data processing. The SH of the miniaturized Mossbauer spectrometer MIMOS II has the dimensions (5 x 5.5 x 9.5) cm and weighs only ca. 400 g. Both 14.4 keV y-rays and 6.4 keV Fe X-rays are detected simultaneously by four Si-PIN diodes. The mass of the electronics board is about 90 g [36],... 

The field of view for the ultrasound equipment is rather small, typically, not more than 20-30 cm and just a few centimeters at higher spatial resolution. Normally, a cross-sectional image in the plane of the imaging probe is obtained. Respectively, the operator must know where to place the transducer to locate the area of an expected lesion, as compared with a whole-body CT, the wide flat view of planar X-ray or MRI scans. 

Non-destructive methods include holographic interferometry, resistance transducers, stress-sensitive covers, and other similar techniques. In practice, the following physical methods of non-destructive monitoring of residual stresses are commonly used X-ray diffraction, measurement of dielectric properties, and ultrasonic control. The main purpose of these methods is to monitor the structural transformations or distortions taking place as a result of residual stresses and local deformations. However, the application of methods such as X-ray diffraction to measure distortions in unit cel dimensions, ultrasonics to measure elastic wave propagation velocities, etc., all encounter numerous experimental problems. Therefore, in ordinary laboratory conditions only quantitative estimations of residual stresses can be obtained. 

Many recent papers are ignored or mentioned only briefly because they are discussed elsewhere in this book. The biological applications of spiropyrans incorporated into membranes and their use as specific ion recognition sensors and signal transducers is discussed in Volume 2, Chapter 9. Spiropyran-modified artificial monolayer, bilayer, and multilayer membranes whose physical and chemical properties can be controlled by irradiation are discussed in Chapter 1 in Volume 2. The X-ray structures of numerous spiropyrans, the nature of the molecular packing, and the relationship between structure and photochemical behavior is reviewed in Volume 2, Chapter 7. 

X-ray powder diffraction experiments were performed on a Phillips x-ray diffractometer with a Diano interface as described earlier (15). Mossbauer spectroscopy studies were all done at 77K with a homebuilt spectrometer consisting of an Elscint transducer, a Canberra amplifier and multichannel analyzer, and a Nal Harshaw... 

There are other methods of NDI other than X-ray radiography. One of them is ultrasonic NDI. In this technique, ultrasonic waves are used to investigate the interior of a ceramic piece. An ultrasonic transducer placed on the surface of the ceramic piece sends the ultrasonic waves received by a sensor found either within the ultrasonic transducer or at another location on the surface of the ceramic piece. Ultrasonic waves are scattered emd reflected back finm the surfaces and defects within... 

X-ray detectors are transducers that count individual photons. In a photoelectric interaction, the entire incident energy of the interacting photon is stored up in the detector (while in Compton scattering, only a portion of the incident energy is deposited). The detector works with greater accuracy, as the photon flux is weaker. The two most current types are ... 

The gas transducer working as a proportional counter. Each X-ray photon provokes an ionization in a gas mixture (e.g. argon/methane) which gives a pulse proportional to its energy (Eigure 12.8). 

The semi-conductor transducer (scintillation counter). Each X-ray photon increases the conductivity of the active zone (the junction) of a lithium-doped silicon diode (one electron for around 3.6 eV). The background noise is reduced if the sensor is maintained at low temperature (cooled by liquid nitrogen or a Peltier device). The entry surface is protected by a beryllium film of a few pm (transparent for Z > 11) (Figure 12.8). In one or other cases the impulse furnished by the detector allows to go back to the energy of the incident photon. 

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