Nuclear bremsstrahlung

There are two processes where nuclear and atomic contributions are iaterrelated. These are the emission of electrons from the atomic shells as an alternative to the emission of a photon and the emission of bremsstrahlung photons ia the P decay process. 

The sources used in Ni Mossbauer work mainly contain Co as the parent nuclide of Ni in a few cases, Cu sources have also been used. Although the half-life of Co is relatively short (99 m), this nuclide is much superior to Cu because it decays via P emission directly to the 67.4 keV Mossbauer level (Fig. 7.2) whereas Cu ti/2 = 3.32 h) decays in a complex way with only about 2.4% populating the 67.4 keV level. There are a number of nuclear reactions leading to Co [4] the most popular ones are Ni(y, p) Co with the bremsstrahlung (about 100 MeV) from an electron accelerator, or Ni(p, a) Co via proton irradiation of Ni in a cyclotron. 

Energy loss of electrons above 100 MeV is dominated by nuclear encounters producing bremsstrahlung. This process, characterized by the radiation length R within which most of the energy is lost, is independent of particle energy. 

Nuclear science in particular obtains from laser-driven electron sources a brand new input to perform interesting measurements in the context of many laboratories equipped with ultrashort powerful lasers. The ultrashort duration of these particle bunches represent a further attractive feature for these kinds of studies. In the following, we will focus on nuclear reaction induced by gamma radiation produced by bremsstrahlung of laser-produced electrons in suitable radiator targets. This way is usually mentioned as photo-activation and is particularly efficient for photons of energy close to the Giant Dipole Resonance of many nuclei. 

The various types of accelerators offer the possibility of applying a great variety of projectiles of different energies. The most frequently used projectiles are protons, deuterons and a particles. Some features of the reactions induced by these partieles are summarized in Table 12.4. Neutrons may be produced indirectly by nuclear reactions, y rays are generated as bremsstrahlung in electron accelerators, and heavy ions are available in heavy-ion accelerators. 

S.M SELTZER, J.P. FARRELL, J. SILVERMAN, Bremsstrahlung Beams from High-Power Electron Accelerators for Use in Radiation Processing, IEEE Transactions on Nuclear Science, Vol. NS-30, No. 2, pp. 1629-1633, 1983. 

Rat diets, food and biological CRMs 1 Seal pellets in PE capsules (short-time neutron and photon irradiation), in silica ampoules (long irradiation) [N/MT DA] PAA irradiate with bremsstrahlung, count INAA irradiate (1 min, 20h) in Nuclear reactor, count RNAA after cooling (1 min, 1-2 weeks), fuse, extract I, precipitate Agl, count. [INAA PAA RNAA] [N/MT-INAA N/MT-PAA DA-SEP/ CONC-RNAA] Kucera et al. (2001)... 

Nuclear medicine procedures play a substantial role in patient selection, therapy planning, treatment monitoring and follow-up. F-FDG PET/CT, SPECT with macroaggregated albumin and post-therapeutic bremsstrahlung scintigraphy are the most important techniques used for this purpose. 

Photoneutrons are produced at considerable flux densities in the heavy metal of the bremsstrahlung converter. For example, in the linear accelerator used by the authors, a thermal neutron flux density of some 10 °cm s has been produced in the tantalum converter during normal operation (30MeV, 150 pA). This appears a relatively poor flux density compared to that of a standard nuclear research reactor. Nevertheless, in advantageous cases trace analyses can be performed. For example, routine analyses of several elements in air-dust samples were carried out by activation with photoneutrons (see below). Normally, however, the photoneutron flux is analytically negligible, whether as an analytical tool or as a source of interference. 

Neutrons - neutrons are emitted during nuclear fission and have very great penetrating powers. They can cause intense ionization. Bremsstrahlung - electromagnetic radiations produced by the slowing down of a p particle. They can have considerable penetrating powers. 

Abstract The effects of interactions of the various kinds of nuclear radiation with matter are summarized with special emphasis on relations to nuclear chemistry and possible applications. The Bethe-Bloch theory describes the slowing down process of heavy charged particles via ionization, and it is modified for electrons and photons to include radiation effects like bremsstrahlung and pair production. Special emphasis is given to processes involved in particle detection, the Cherenkov effect and transition radiation. Useful formulae, numerical constants, and graphs are provided to help calculations of the stopping power of particles in simple and composite materials. 

Fast electrons also radiate in the field of the atomic electrons. This electron-electron bremsstrahlung has cross section very similar to that of the nuclear one except that it is proportional to Z instead of Z. Thus, for the total energy loss, one approximately includes electron-electron bremsstrahlung as well ifin the aforementioned equations Z is replaced by Z(Z+ 1) (Leo 1987). 

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