Energy deposition, depth dependence

DEPTH PROFILE. The secondary electrons produced by ionization processes from an incident beam of high-energy electrons are randomly directed in space. Spatial "equilibrium" is achieved only after a minimum distance from the surface of a polymer in contact with a vacuum or gaseous environment (of much lower density). Consequently, the absorbed radiation dose increases to a maximum at a distance from the surface (2 mm for 1 MeV electrons) which depends on the energy of the electrons. The energy deposition then decreases towards zero at a limiting penetration depth. 

Based on the definitions of energy and thermal penetration depth, in material processing, pulses can be classified as short and ultrashort. Pulses for which > 8 are considered to be short. If d < S they are classified as ultrashort (Dirscherl 2008). This definition depends strongly on the material processed, as both thermal conductivity and the energy deposition characteristics... 

Figure 8. Schematic representation of the depth dependence of energy deposition of the double exposure process. Neglecting bleaching, the energy density deposited is described by = pEg 10 + a(l + x/2), where p is the optical absorption coefficient, Eg the incident optical energy per surface unit, x the depth into the resist, and a a coefficient proportional to the incident electron dose Q.

Furthermore, the extraction of non-conventional oil has other detrimental environmental impacts, such as water pollution and loss of biodiversity. Depending on the depth of the deposits, oil sands are either strip mined in open pits or heated so that the bitumen from which the non-conventional oil is extracted can flow to the surface (in-situ extraction). Both forms of oil-sands extraction require considerable amounts of energy (i.e., natural gas) and water, and lead to significant detrimental environmental impacts (Woynillowicz et al., 2005 see also Chapter 3). 

Fig. 4.29. Normalized integrated intensities (left) of substrate core levels in dependence on deposition time for the spectra shown in Fig. 4.26. The deposition rate is estimated to be 2nmmin 1. The lines in the left graph are obtained by curve fitting of the data to an exponential decay. The derived attenuation times are displayed in the right graph in dependence on electron kinetic energy together with theoretical energy-dependent escape depth calculated using the formula by Tanuma, Powell, and Penn [37] and using a y/ E law [38]...

The initiation of sediment movement depends on a supply of energy from raindrop impact, overland or river flow, or a mass movement of soil. Similarly, deposition occurs when sufficient energy is not available to maintain sediment particles in motion. The energy thresholds for initiation and cessation of sediment movement are not the same, being influenced differently by a range of conditions such as flow depth, velocity and turbulence, and sediment characteristics such as cohesion, particle shape and particle density. 

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