Counters Geiger-Mueller

Other techniques for the diffusion of gas through monolayers at the liquid interface have also been investigated (Blank, 1970). In these methods, the differential manometer system was used to measure the adsorption of gases such as C02 and 02 into aqueous solutions with and without the presence of monolayers. The Geiger-Mueller counter with a suitable sorbent and a radioactive tracer gas was used to measure the reduction of evolution of H2S and C02 from the surface solution when a monolayer was present. 

In a recent work, Aiba (A2) studied the flow currents in water, in a mixing vessel 14 in. in diameter, using an axially-mounted two-bladed flat paddle 4.7 in. in diameter. Measurements were made both without baffles and with four baffles %2 tank diameter wide. A sphere about 6 mm. in diameter was suspended by a flexible wire, and its displacement from the equilibrium (no-flow) position was measured. To get the horizontal displacement, cobalt-60 was embedded in the sphere, and a Geiger-Mueller counter approximately 10 mm. in diameter was immersed in the tank 2-5 cm. from the sphere. The vertical movement of the sphere was measured with a cathetometer, and its angular position observed by eye. From the known components of displacement and the assumed drag coefficient of the sphere, values of the radial, tangential, and vertical components of the flow around the sphere were calculated. 

In these runs, the presence of the Geiger-Mueller counter may affect the flow pattern significantly. Further, examination of the results presented shows that the radial velocities do not satisfy material balance requirements. Nevertheless, several of Aiba s conclusions are of interest. With baffles, the vertical circulation is large compared with the unbaffled case, but considerable tangential flow remains. In neither the baffled nor unbaffled case do the mean flow velocities approach the tip velocity of the impeller the ratio of fluid velocity to impeller-tip velocity is essentially independent of impeller rotation speed, varies... 

M9. Matthews, K., Two-transistor Geiger-Mueller counter quench circuit. Rev. Sci. Instrum. 40, 1511-1512 (1969). 

The astatine vapor is invisible, but since it is radioactive we can count its nuclear disintegrations with a Geiger-Mueller counter. 

E. Because of the weak beta radiation, tritium is NOT readily measured by the Geiger-Mueller counter used with most fielded radiac instruments and requires wipe testing swipes and a liquid scintillation detector to determine the level of contamination. 

Hans Geiger worked in Ernest Rutherford s laboratory manually and meticulously counting a-particle scintillations for the famous experiments that led to the discovery of the nucleus. Because of this work, he developed an a-particle detector. After World War I, Geiger developed the modern Geiger-Mueller counter and worked until his death to increase its speed and sensitivity. 

Fig. 19.1 Half a century ago, measurement of radioactive Iodine In the thyroid gland with a Geiger-Mueller counter placed at different points indicated...

Zumwalt, L. R. 1950. Atomic Energy Commission Report AECU-567. Absolute beta counting using end-window Geiger-Mueller counters and experimental data on beta-particle scattering effects. Washington, DC AEC. 

The radioactive decay of an unstable nucleus is a random process. In any given interval of time, there is a well-defined probability that a given nucleus will decay. This probability is independent of time and is the same for aU nuclei of a given type, but is different for different isotopes. The number of nuclei decaying per unit time is the rate of nuclear decay (or activity), which can be measured using devices, such as the Geiger-Mueller counter (Figure 17.4). 

Figure 17.4 Schematic diagram of a Geiger-Mueller counter. Radiation (a-, fi-, or y-rays) entering through the window ionizes the argon gas to generate a small current between the electrodes. This current is amphfied and is used to flash a light or operate a counter with a clicking sound.

A major advantage of using radioactive isotopes as tracers is that they are easy to detect. Their presence even in very small amounts can be detected by photographic techniques or by devices known as counters, such as the Geiger-Mueller counter pictured in Figure 17.4. 

Geiger-Mueller Counter Kanne Ionization Chamber Boron triflouride proportional counter Sodium Iodide b... 

Monitoring occupational radiation exposure is a fundamental aspect of radiation protection. This can be done by measuring radiation fields with a common handheld instrument such as a Geiger-Mueller Counter and, if exposure conditions are predictable and relatively low (i.e., less than 10% of the regulatory limit), expected exposures can be calculated and documented. Alternately, regular radiation field survey measurements can be performed, and personnel dosimeters are issued to workers. 

A phosphorus pellet, made of red phosphorus and the same size as the sulfur pellet, is used for the calibration of the end-window Geiger-Mueller counter. The amorphous red phosphorus powder is mixed with a small amount of binder ( 4 w/o polyvinyl alcohol powder) before being pressed. The pressed pellet is also sprayed with Krylon. 

The gold foil is counted with a calibrated Geiger-Mueller counter which has been calibrated previously by use of a standard pile of known flux. From this measurement, the thermal flux in which the phosphorus was irradiated can be determined. The phosphorus pellet is then counted with the end-window counter. As previously stated, the range of the beta particle determines the active weight which is counted. The counting rate is given by... 

The manganese foil discs and the sodium pellets do not require an absolute measurement of activity, since only their cadmium ratios are necessary for the experiment. The manganese will be counted with an end-window Geiger-Mueller counter, and the sodium with the Nal scintillation counter. 

The standardization of the end-window Geiger-Mueller counter with standard gold foil ( 50 mg/cm ) is given in Table 28.2. The listed values are for the standard foil holder in three shelf positions no absorber was used. 

The sulfur threshold detector is used to measure the integrated fast flux above 2.9 MeV. In Part B, the equation used to determine the fast flux is derived in conjunction with a phosphorus-pellet calibration of the Geiger-Mueller counter ... 

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