Gamma rays definition

In MWD, the recording speed is the rate of penetration which rarely exceeds 120 to 150 ft/hr or 2 to 2.5 ft/min, two orders of magnitude less than the logging speed. Counters can be made shorter and time constant longer (up to 30 s or more). This results in a better accuracy and a better bed definition. Figure 4-269 shows an example of comparison between an MWD gamma ray log and the wireline log ran later. 

In a joint program conducted between PlcArsn and Brookhaven National Laboratory, Abel et al (Refs 49 63) studied the effect of reactor and gamma-ray irradiation on the impact sensitivity of colloidal Pb azide. With reactor irradiations ranging from 3.3 x 1017 to 1.57 x 1018nvt (n/cm2) (fast plus slow neutrons) and the accompanying reactor gamma dose rate of 2 x 106R/hr the effects are shown in Fig 4. The results indicate that there is a definite increase in the impact sensitivity of colloidal Pb azide as a function of total neutron dose. The studies... 

There is not yet, however, a definite detection of diffuse gamma-ray emission from galaxy clusters. While there is a preliminary evidence of gamma-ray emission from a dozen bright, radio-active clusters which host powerful radio galaxies and Blazars and are associated to unidentified EGRET sources (Co-lafrancesco 2002), many of the quiet, X-ray selected clusters only have upper limits for their emission at E > 100 MeV. 

Radiographing metals to determine weld quality. (Iridium-192, with a 0.3 MeV gamma ray, provides better definition than Co-60 in some cases but has a shorter half-life.)... 

The efficiency of a detector is a measure of how many pulses occur for a given number of gamma rays. Various kinds of efficiency definitions are in common use for gamma ray detectors ... 

Both ionic and free radical mechanisms can be written to explain the foregoing reactions in more detail, but these would be strictly speculative, since no definitive experimental evidence has been obtained. Some sort of benzene ion must form as a result of inelastic collisions between the electrons and benzene molecules in the plasma, but whether these ions or some derivative species are the reactive intermediates is not known. Recently, Potter et al. (11) have shown that styrene, when perfectly dry, does polymerize via an ionic mechanism when irradiated with gamma rays. One can picture a similar mechanism occurring in the electrical discharge. 

Boyce R.E., 1976. Definitions and laboratory techniques of compressional sound velocity parameters and wet-water content, wet-bulk density, and porosity parameters by gravity and gamma ray attenuation techniques. In Schlanger S.O., Jackson E.D. et al (eds) Initial Reports of the Deep Sea Drilling Project 33, Washington, US Government Printing Office, pp 931-958... 

With COMPTEL on the Gamma-ray Observatory, the concept has definitely proven its unique potential for MeV gamma-ray astronomy (Schonfelder et al. 1993). 

The PAC experiment makes use of a nucleus which decays through successive gamma radiations yj and yj- The observation of yj in a fixed direction determines the spin orientation of the nucleus and the subsequent radiation j2 then has a definite angular correlation with respect to the direction of yj. If in the intermediate state of the gamma-ray cascade the nucleus is under the influence of a magnetic hyperfine interaction, the second radiation y2 carries with it information on this interaction. Hence the relaxation of the environment within the lifetime of the intermediate state of the nucleus manifests itself in a time-dependent magnetic hyperfine interaction. 

Readers may notice the absence of certain terms in common use. The exclusion of some such terms is a deliberate choice. For example, instead of photopeak we prefer full-energy peak we have avoided the statisticians use of error to mean uncertainty and reserve that word to indicate bias or error in the sense of mistake . Branching ratio we avoid altogether. This is often used ambiguously and without definition. In other texts, it may mean the relative proportions of different decay modes, or the proportions of different beta-particle transitions, or the ratio of de-excitation routes from a nuclear-energy level. Furthermore, it sometimes appears as a synonym for gamma-ray emission probabihty , where it is not always clear whether or not internal conversion has been taken into account. 

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