Neutral beam attenuation

In the context of hydrogen neutral beam attenuation kinetics in fusion plasmas, and charge exchange core plasma diagnostics, the important hydrogen atom processes are those with highly stripped impurity ions, Aqz (where Z is the atomic number of impurity, and q is its charge)... 

X-ray and neutron imaging are complementary techniques for materials research. X-rays interact mainly with the electronic shell of atoms whereas neutrons as charge-neutral particles interact with the nuclei (Figure 18.1a,b). The different interaction mechanisms yield different beam attenuation properties. Figure 18.1c shows the values for the attenuation coefficients of X-rays and neutrons for different element numbers. In the case of X-rays, the attenuation increases with the number of electrons in the atom and, therefore, with the element number. In case of neutrons, no clear dependence on the amount of nuclei within the atomic core can be found. In contrast to X-rays, some light elements such as H and Li have a very... 

A photolysis time of 5 to 10 min should be aimed for and may first be established with the model compound by varying the distance of the sample container from the lamp (for an uncollimated source) or by attenuating the source with neutral density filters (for a collimated beam). This duration is conveniently short and yet not so brief that split-second timing is required for reproducible results. 

Attenuance filter An optical device (filter) which reduces the radiant power of a light beam by a constant factor over all wavelengths within its operating range. Sometimes called attenuator or neutral density filter. 

Bathypho tome ter Detector. The submersible system, which employs the same basic approach of pumping seawater past a PMT, also consisted of an RCA 8575 PMT used in the photon count mode, a filter-wheel disc with a capacity for carrying 20 optical filters, a temperature thermistor, a beam transmissometer, and a depth sensor. The central wavelengths of the optical filters used were 360, 370, 380, 390, 400, 420, 440, 460, 480, 500, 520, 540, 650, 580, 600, 620, and 640 nm. Neutral-density filters of varying attenuation powers complemented the filter set, and all components were contained in an aluminum pressure housing (Figure 2). 

Neutral-density filters are used to reduce the intensity of a light beam in a well-defined way, e.g. for testing the linearity of an optical detector. Filters of this kind should have a constant attenuation over large spectral ranges to facilitate their use. Normally, semitransparent metal films of chromium or nickel on quartz substrates are used. A filter is characterized by its transmittance T, or optical density D. D and T are related according to... 

When a Morton neuroma is suspected on clinical grounds, we select a dorsal approach to examine the web spaces because the skin (and especially the stratus corneus of the epidermis) over the dorsum of the foot is thinner than that of the sole and the attenuation of the US beam is less. The patient lies supine or seated on the bed with the knee extended and the ankle in a neutral position. The intermetatarsal spaces should be examined in sagittal planes applying firm pressure with the transducer on the dorsal aspect of the foot while exerting finger pressure in the web spaces from the plantar surface (Fig. 17.50). The thumb of the hand not holding the probe works well for this purpose. The examiner should invite... 

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