Bremsstrahlung irradiation

The excited initial state can be produced either directly or by means of radiative cascades and non-radiative transfers. The first is the most probable process, i.e. a filling up by direct inner shell excitation. As a consequence, the R lines are observed only when the hole is created by electron bombardment and not by bremsstrahlung irradiation 12). 

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. 

Fig. 8.8. Experiment set-up and obtained results. Counter-clockwise, from top left schematic view of the set-up for the activation experiment, accelerated electron spectrum as measured by a magnetic spectrometer, full differential cross section for the reaction 197Au(7, n)196Au (dotted) and bremsstrahlung spectrum reconstructed after the deconvolution calculations (solid), x-ray emission spectrum of 196Au measured after the gold sample irradiation...

Whether the radiation source is a machine-generated e-beam, isotopic gamma rays, or machine-generated x-rays (bremsstrahlung), a continuum of x-rays and electrons is produced as the initial event dissipates its energy in the irradiated medium. This chapter will focus on an e-beam source, as this is the most likely source to be used in a waste-treatment application. It should be noted that most of the comments made here are equally applicable to other sources of radiation. 

Photon energy. Photons are produced exclusively by bremsstrahlung. The latter phenomenon takes place only in the case of beta irradiation. However, it also occurs in the case of gamma irradiation and, to a lesser extent in the case of irradiations by protons, deutons, and alpha particles, as a consequence of secondary beta rays emitted by these particles. 

M. TAKEHISA, T. SAITO, T. TAKAHASHI, Y. SATO, T. SATO, Characteristics of a Contract Electron Beam and Bremsstrahlung (X ray) Irradiation Facility of Radia Industry, Radiation Physics and Chemistry, Vol. 42, Nos. 1-3, pp. 495-498, 1993. 

Part-per-billion levels of molybdenum can be measured by neutron activation. After two or more hours irradiation at a neutron flux of 1012 n cm"2 sec 1, the principal gamma at 141 KeV [98Mo(n,y,p) 99mTc] is readily measured. In crude oils, however, some Bremsstrahlung interference may be encountered as a result of activated sulfur or chlorine. 

PAA Photon activation analysis involves irradiation with high energy photons (produced by conversion of electron energy into bremsstrahlung serving as the source of the photons). Photons emitted in the delayed decay are detected and used as the analytical signal. 

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)... 

In the following example, gasoline was irradiated with the bremsstrahlung x-rays from a 2 MeV electron beam (Zaikin and Zaikina 2007). The experiments have shown that radiation-enhanced isomerization became especially pronounced when heavy aromatic hydrocarbons were added to relatively lighter feedstock and this mixture was irradiated with moderate x-ray doses. In these experiments, heavy residua of bitumen radiation processing were used as additional agents for enhanced isomerization. 

FIGURE 15.5 Fractional contents of gas-condensate gasoline after Bremsstrahlung x-ray irradiation. GCG, gas-condensate gasoline. 

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