Radiation Gauges

Radiation-type level detectors can be point source, multiple source, strip source, motorized tape-supported traveling source, or backscatter types with cesium-137 or cobalt-60 (for thick-walled tanks) source materials. The ranges of external units are up to 7 m (23 ft) and of the traversing backscatter-type units up to 45 m (150 ft). Measurement errors range from 6 mm to 1% FS. 

The relative penetrating powers of the three kinds of radiation are approximately in the range of 1,100, and 10,000 for the alpha, beta, and gamma rays, respectively. The penetrating power of alpha rays is less than 0.2 m (8 in.) of atmospheric air. Beta radiation can penetrate approximately 6 mm (0.25 in.) of aluminum. Gamma rays are used for level measurement because of their high penetrating power, and because they cannot be deflected. 

Radiation-based level detection continues to be very appealing for cryogenic, hard-to-handle, toxic, and corrosive processes, because it does not require vessel wall penetrations. Costs and licensing requirements do limit the number of applications but are not serious impediments to the implementation of carefully designed systems. 

Radiation reduction (NB) as a function of the source material, the material that the narrow-beam radiation is passing through, and of the thickness of this material. So, for example, if the source is Cs-137, which is passing through a l-in.-thick steel plate, NB = 4, and therefore, the field intensity will be reduced to 25%. 

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As in the spin 0 and spin case we could next introduce creation and anniliilation operators. This is most conveniently done by working with the representatives that satisfy in a given Lorentz frame the three dimensional transversality condition, i.e., by working in the radiation gauge. We shall, however, adopt a slightly different procedure, which is outlined in the next section. 

For very hard-to-handle process fluids nuclear radiation gauges are used to detect interfaces and levels. 

Activation (or radioactivation) analysis 1 A99— A100 see Radiation gauging in energetic matls 9 R76-R103, also Radioactive tracers 9 R104-R113... 

With the availability of small, relatively intense radioisotopic neutron sources, radiation gauging with neutrons has become an important technique in the inspection of energetic materials. Applications have included nondestructive measurement of moisture in expls, determination of charge weight and fill height in sealed ammo cartridges and in detection of concealed expls... 

Corporation of San Diego, California, began the development of an automated radiation gauging inspection system for large caliber artillery shell intended to replace the X-ray technique. The system was named AIDECS for Automatic Inspection Device for Explosive Charge in Shell and is still in the process of test and development as of this writing. The ultimate objective is to produce a system capable of making accept/reject decisions on a production basis at a rate of about 1 minute per shell... 

On hard-to-handle services, such as the fluidized-bed level measurement in combustion processes, there is little choice but to use radiation gauges. On slurry and sludge services, d/p units with extended diaphragms eliminate the dead-ended cavity and bring the sensing diaphragm flush with the inner surface of the tank. Other level transmitters that can be considered for hard-to-handle services include the capacitance/RF, laser, radar, sonic, and TDR types. 

When the application involves foaming, one must detect both the liquid-foam interface and foam level. Radiation sensors can detect the liquid-foam interface and TDR transmitters, or conductance and RF switches can detect the foam level if it is conductive. In the case of heavier foams, vibrating or tuning-fork switches and beta-radiation gauges have been used in some cases, optical or thermal switches have also been successful. 

This can be accomplished in two ways (i) via a canonical transformation of the Hamiltonian (7) and its (perturbed) eigenstates, assuming the radiation gauge (2) [24-26],... 

Helf [72] described the technique of radiation gauging in energetic materials. 

Radiation gauging pertains to the use of penetrating radiation, in particular as emitted from radionuclides or radioactive isotopes, for the measurement of particular properties of a material or system. Such properties may include density, thickness, mass, volume, composition, uniformity, etc. In addition to the use of nuclear radiation from radioisotopes instead of X-rays from machine generators, the other distinguishing difference from Radiography is that electronic detectors are employed instead of flhn to measure the transmitted or scattered radiation... 

The through-transmission y-radiation gauging technique is the most direct approach to nondestructively determining local volume fractions of reinforcement, resin, and porosity in composite systems. 

In this book we will mostly employ the Coulomb gauge of Eq. (2.133), which is also called transverse or radiation gauge. With this choice of gauge Eq. (2.128) is reduced to Poisson s equation... 

The thickness of the cast film is controlled by the extruder output, the die gap, and the amount of draw between the die and the chill roll. The die gap is regulated by a series of adjusters across the width of the die, each of which may be adjusted independently to ensure uniform film thickness. Film thickness is scanned continuously during production, using a noncontacting p-radiation gauging device. The die gap may be adjusted automatically on the basis of feedback from the gauging device. The amount of draw experienced by the molten polymer is controlled by the rate of rotation of the nip rolls and chill roll relative to the die output. 

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