Compton effect, gamma rays from

The attenuation coefficient for a beam of gamma rays is related to the number of gamma rays removed from the beam, either by absorption or scattering. For the Compton effect, the absorption cross section is determined by the energy absorbed by the electron, which is the total collision energy minus the average scattered photon... 

Gamma-rays of higher energy, rather than interacting with the field of the whole atom as in the photoelectric effect, interact with the field of one electron directly. This mode of interaction is called the Compton effect after its discoverer, A. H. Compton. In the Compton effect an electron is ejected from an atom while the y-ray is deflected with a lower energy. The energy of the scattered y-ray, Ey, is expressed by the equation... 

One method in which this division is explicit is maximum entropy (Max-Ent) which has proved to be very effective in producing images from the COMPTEL instrument on the Compton Gamma Ray Observatory CGRO. In this paper I briefly describe MaxEnt and illustrate applications to COMPTEL data for imaging of continuum emission from point sources and for imaging the full sky. Applications to line emission are covered by R. Diehl in an accompanying paper. I also mention some new developments in Bayesian methods. 

Compton s physics was first-rate, as Fermi s respect implies. He graduated from the College of Wooster and took his Ph.D. at Princeton. In 1919, the first year of the program, he was appointed a National Research Council fellow and used the appointment to study under Rutherford at the Cavendish. The difficult work he began there—examining the scattering and absorption of gamma rays—led directly to the discovery of what came to be called the Compton effect, for which he won the Nobel Prize. 

The probability of fhese interactions depends not only on the energy of the gariuna ray but also on the atomic number, Z, of the material. Figure 25.6 plots the relative probability of Compton interactions, a, with photoelectric effect, t, and pair production, k. Higher Z materials, such as lead are more likely to have photoelectric effects than Compton scattering. From the standpoint of shielding gamma rays, photoelectric effect is preferable as discussed later. 

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