Detection and Counting

WDSs have excellent resolving power, and the peak-to-background ratio of each line is much higher than can be achieved with a crystal detector. With a suitable crystal of large lattice spacing it is possible to detect and count X-rays as soft as boron K or even beryllium K , and this type of spectrometer is widely used when... 

An older and long-established technique, radiocarbon decay counting, also known as the "conventional" method of radiocarbon dating, is based on detecting and counting the amount of beta radiation emitted in unit time by radiocarbon atoms in a sample of known weight. 

In almost every case, experimenters who use the resonant nuclear reactions have chosen to detect and count the gamma rays, but the alpha particles can also be used (Umezawa et al., 1987, 1988a). There seems to be no published comparison of the results using alpha particle and gamma ray detection. Fig 2 shows a typical experimental setup using a gamma ray detector. 

Organic media are suitable for detecting and counting radioactivity by scintillation methods, because the quenching of scintillation in organic... 

Contact plates are used when sampling regular or flat surfaces. The test is performed with RODAC (replicate organisms detecting and counting) plates, or contact plates, where the convex agar surface rises above the brim of the plate. 

Although radioactivity is defined in terms of nuclear disintegrations per unit of time, rarely does one measure this absolute number in the laboratory. Instruments that detect and count emitted particles respond to only a small fraction of the particles. Data from a radiation counter are in counts per minute (cpm), which can be converted to actual disintegrations per minute if... 

The X-ray photons selected by the monochromator are detected and counted by a gas flow proportional counter and a measurement chain designed to amplify the impulses supplied by the counter and shape them for subsequent manipulation. 

Condensation nucleus (CN) concentration CN counter Expose particles to a high supersaturation, typically of butanol vapor particles grow to size where they can be optically detected and counted -b... 

Depending on the goals, a variety of procedures can be used to facilitate particle detection. In condensation particle counters (also called condensation nucleus (CN) and Aitken nucleus counters), particles as small as 3 nm diameter are detected through size enhancement and optical detection. The particles are introduced into a chamber that contains a supersaturated vapor (water or n-butyl alcohol is commonly used). Condensation on the particles enlarges them typically to several micrometers so that they can be readily detected and counted as they pass through the chamber. 

The purpose of XPS analysis is then to detect and count these photoelectrons using a detector which allows to measure the photoelectrons cuirent density as a function of their kinetic energy. Obviously the kinetic energy of the photoelectrons having not been involved... 

Rutherford and his students used a screen coated with zinc sulfide to detect the arrival of alpha particles by the pinpoint scintillations of light they produce. That simple device has been developed into the modern scintillation counter. Instead of a ZnS screen, the modern scintillation counter uses a crystal of sodium iodide, in which a small fraction of the Na ions have been replaced by thallium (TH) ions. The crystal emits a pulse of light when it absorbs a beta particle or a gamma ray, and a photomultiplier tube detects and counts the light pulses. 

There are three basic methods which have been employed for evaluation of microbiological content on surfaces. These include ROD AC (Replicate Organism Detection and Counting) plates, swab testing, and agar overlay or rinse techniques. RODAC plates are the most commonly used of the surface monitoring methods. However, they are not suitable for irregular surfaces, in which case swab techniques are used. 

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