Internal Gas Counting

Internal gas counting requires that corrections be made for wall and end effects and for the decrease in electric field intensity at the ends. One way to reduce the end effect is to use a spherical proportional counter, in which the anode wire is stretched along a diameter and the cathode is, of course, spherical. The electric field inside the sphere is 

At a certain distance r from the anode, the electric field becomes stronger at the ends of the anode because b, the radius of the cathode, gets smaller. However, the supports of the wire tend to reduce the field. By property adjusting the supports, one may make the field uniform. In cylindrical counters, corrections for end effects are applied by a length-compensation method. Internal gas counting is used for the production of standards. Using this technique, the National Bureau of Standards produced standards of H, C, A, K, Xe, and Xe. 

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The plutonium solution concentration was determined by alpha counting 0.5-ml. aliquots evaporated to dryness on planchets. Gas flow internal proportional counting was used with 90% argon-10 % methane gas and Nuclear Measurement Corp. counters. 

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. 

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. 

As proportional counters have dead times of only several ps, high counting rates can be measured without losses. Because the internal counting efficiency of proportional counters for y radiation is low (about 1%), they are not suited to measure y radiation. However, proportional counters of special design and operating at high gas pressure are applied to X-ray and low energy y-ray spectrometry. 

The plutonium concentration in the ambient sorbing solutions was determined by alpha counting an evaporated aliquot in a gas flow internal proportional counter, also previously described (I). The amount... 

The blistering caused by mustard gas is due to the high local concentrations of HCl that are produced when water—or any other nucleophile—reacts with the gas when it comes into contact with the skin or lungs. Autopsies of soldiers killed by mustard gas in World War I—estimated to be about 400,000— showed that they had extremely low white blood cell counts, indicating that the gas interfered with bone marrow development. An international treaty in the 1980s banned its use and required that all stockpiles of mustard gas be destroyed. 

A large international collaboration ("Gallex ) is setting up a neutrino detection station in a rock facility in the Mont Blanc. Some Ga atoms in 30 tons of gallium metal is expected to react with solar neutrinos to form Ge (t, 11.4 d) which is to be converted to the gaseous hydride, GeH, and counted in a proportional detector. About 1 atom of Ge formed per day is expected. 

Perhaps a chemical analogy to this state of affairs can be drawn. The file storage systems would be the equivalent of a container filled with an inert gas. Being "inert", the individual atoms of this gas hardly interact with one another, and apart from a count of the total number of atoms, little further structure to the collection can easily be discerned. Molecules are certainly unlikely to form under these conditions, and nor will it be easy to crystallize this collection into something with a well defined structure and with internal relationships. 

Such a transformation is already taking place in the world gas market (Jensen, 2003). More international oil companies are investing in major natural gas infrastructure projects without the security of fully finalized sales for total output volumes. Instead, companies are counting on their own ability to identify end-use markets at some future time, closer in line to the investment pattern that characterizes development of multi-billion dollar oil fields. Expectations of a premium, liquid US market are a key factor encouraging this change as was liberalization of certain European markets which allowed gas sellers to bypass European state gas monopolies and sell directly to large gas customers and power generators (see Shepherd and Ball, 2006). 

The first type is a manual detector, either with a thin (typically 80 qg/cm ) window beneath which the sample is placed, or without a window but with a sample tray that slides under the detector and becomes the detector bottom. Use of the internal proportional counter eliminates external attenuation of low-energy beta particles but introducing the source into the detector can cause contamination or reduce the potential difference to a value below the applied voltage. The detection volume may be cylindrical (typically about 1 cm high and 3 cm in radius), or may be a hemisphere in the classical 27rgroportional counter. For either a thin window or no window, continuous gas flow is maintained. A thicker window (typically 0.5 mg/cm ) can seal the counting gas in the detector. 

A compartment is divided into two control volumes, a relatively hot upper layer and a relatively cool lower layer, as illustrated in Fig. 4. The gas in each layer has attributes of mass, internal /energy, density, temperature, and volume denoted respectively by m, Ei, ni, Ti, and Vi where i = Lfoi the lower layer and / = U for the upper layer. The compartment as a whole has the attribute of pressure P. These 11 variables are related by means of the following seven constraints (counting density, internal eneigy and the ideal gas law twice, once for each Iayer)[14]. 

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