Geiger counting

The analysis of these samples may be carried out by a variety of techniques, and we chose the technique simplest for us, because we had an internal gas geiger counting system already calibrated for Kr-85 and in operation in our laboratories for other purposes. 

The second major technique of radioactivity quantitation is gas flow or Geiger counting. This method is based on the production of ion pairs when particles are permitted to pass through a noble gas such as argon... 

Figure 3-41. Determination of the optimal operating voltage (arrow) within the Geiger counting region for gas flow counting.

Output formats Cuvette or plate reader, microscope images, videos, radioactivity (scintillation or Geiger counting) Plate reader— Usts formats suitable for automated deposition into databases for processing and visualization. HCS—image files and calculated parameters and metadata... 

An important field of application of the theory of deviations is the subject of radioactivity. Here it is a question of counting the number of particles emitted by a radioactive preparation per second (e.g. by means of a Geiger counting apparatus (p. 32)). If we are dealing with a long-lived substance, for which the average number (n) of... 

Acetal copolymer Nylon 6 Nylon 12 Nylon 66 Polybutylene terephthalate Polyethylene, ultrahigh m.w. high-density Polyurethane elastomer, thermoplastic geiger-counting tubes Argon gel coats... 

Advantages of scintillation counting over Geiger counting are discussed below. 

Geiger counter an instrument for counting radioactive particles based on their ability to ionize an inert gas such as Ar. (p. 643)... 

Alpha counting is done with an internal proportional counter or a scintiUation counter. Beta counting is carried out with an internal or external proportional gas-flow chamber or an end-window Geiger-MueUer tube. The operating principles and descriptions of various counting instmments are available, as are techniques for determining various radioelements in aqueous solution (20,44). A laboratory manual of radiochemical procedures has been compiled for analysis of specific radionucHdes in drinking water (45). Detector efficiency should be deterrnined with commercially available sources of known activity. 

A Geiger counter counts 0.070% of all particles emitted by a sample. What is the activity that registers 19.4 X 103 counts in one minute ... 

Fluorine-18 has a decay constant of 6.31 X 10-3 min-1. How many counts will one get on a Geiger counter in one minute from 1.00 mg of fluorine-18 Assume the sensitivity of the counter is such that it intercepts 0.50% of the emitted radiation. 

Because the Geiger counter produces pulses independent in size of x-ray wavelength, it is the best detector for the method of counting that employs a capacitor to accumulate the individual counts (2.3, 2.10). 

Intensity measurements are simplified when a detector always gives one electrical pulse for each x-ray quantum absorbed the detector remains linear so long as this is true. For low intensities, when the rates of incidence upon the detector are low, the Geiger counter fulfills this condition. As this rate increases above (about) 500 counts per second, the number of pulses per second decreases progressively below the number of quanta absorbed per second. This decrease occurs even with electronic circuits that can handle higher counting rates without appreciable losses. 

The cause of this difficulty therefore resides within the counter itself. The difficulty is described by saying that the Geiger counter has a dead time, by which is meant the time interval after a pulse during which the counter cannot respond to a later pulse. This interval, which is usually well below 0.5 millisecond, limits the useful maximum counting rate of the detector. The cause of the dead time is the slowness with which the positive-ion space charge (2.5) leaves the central wire under the influence of the electric field. This reduction in observed counting rate is known as the coincidence loss. 

The tube of Figure 2-2 can be operated as an ionization chamber, as a proportional counter, or as a Geiger counter. The tube output differs radically from one case to another. Because of these differences, the electronic circuitry associated with the tube must also be different for each case if the pulses from the tube are to be reliably selected and counted. In particular, the circuitry will have to differ in characteristics such as stability, amount of amplification, and time of response. In all cases, linear amplification (amplifier output always proportional to tube output) is desirable. 

Geiger counter for routine diffraction and other work involving low counting rates. 

These data are plotted in Figure 10-3 about the Gaussian curve for which the standard deviation is the square root of the mean. The data of Rutherford and Geiger, which were obtained by counting alpha-particles, are plotted about the same curve. In the figure, both sets of data fit the Gaussian about equally.well. 

Counter, Geiger-Mueller (GM counter)—Highly sensitive, gas-filled radiation-measuring device to detect (count) individual photons or particulate radiation. 

All gaseous sulfur products obtained as a result of incubation of sulfur-treated fruit were oxidized with alkaline hydrogen peroxide, precipitated as barium sulfate, and counted with a thin window Geiger counter. The peel and peel proteins were oxidized with magnesium nitrate, the sulfur was precipitated as barium sulfate according to standard methods, and counted as in the case of the gaseous products. Counting data, as reported, are fully corrected. 

Gas Ionization Counters A common gas ionization counter is the Geiger-Muller counter where the electronic pulses derived from the ionization process are registered as counts. The instrument can be adjusted to detect only radiation with a desired penetrating power. 

A sample of iodine-128 was produced in a Szilard-Chalmers reaction by irradiating a sample of ethyl iodide in a neutron source. The radio-iodine was extracted with sodium thiosulfate solution and then counted in a Geiger counter at various time Intervals. Use the tabulated data of t in minutes against C counts/min to find the rate equation and the half time. 

Rutherford, E. and Geiger, H. (1908). An electrical method of counting the number of alpha particles from radioactive substances. Proceedings of the Royal Society A81 141-161. 

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