FORMATION OF TRACK ENTITIES BY PHOTONS IN WATER

To study the photon-induced formation of track entities in water, the photon attenuation in, and the penetration through, an infinitely exte nded water medium was simulated using the Monte Carlo method. Four int eraction processes were involved: the photoelectric effect, coherent a nd incoherent scattering, both taking electron binding into account, a nd electron-positron pair creation followed by the annihilation proces s of positrons. Conventional sampling techniques were used to calculat e the spectral distribution of secondary electrons produced by photons of energies between 10 keV and 10 MeV as a function of the number of photon interactions along the photons' paths. After this, to look into the photons' track structure, the electron distributions produced wer e classified according to the well known 'track entity' concept of Moz umder and Magee(1). In the course of this it turned out that the photo n-induced formation of track entities is quite different from that of primary electrons. Whereas the number of track entities induced by pri mary electrons is nearly proportional to the primary particles' energy , the photon-induced number of track entities is practically independe nt of the photon energy.