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. 2011 Jun 23;38(7):4127–4132. doi: 10.1118/1.3592646

Figure 4.

Figure 4

Cerenkov emission induced by electrons and photons with varying energies and field sizes. In (a)–(e) Cerenkov emission due to an electron beam with a circular field size (diameter 3 cm) at 6 MeV, 9 MeV, 12 MeV, 15 MeV, and 18 MeV respectively. In (f)–(j) Cerenkov emission due to an electron beam with a square field size (4 × 4 cm2) at 6 MeV, 9 MeV, 12 MeV, 15 MeV and 18 MeV respectively. In (k)–(l) Cerenkov emission induced by x-ray photons with a square field size (2 × 2 cm2) at 6 MV and 18 MV, respectively. In (m) the average of the intensity within a square region of 1 cm2, centered at the maximum intensity pixel of each image shown as a function of electron energy, (•) electrons with circular field size, (▪) electrons with quadratic field size and (▴) photons with square field size. The photon beam energies, at 6 and 18 MV, are replaced by the average secondary electron energies (originating from Compton or photoelectric interaction), given by 1 and 3 MeV. The bars in (a)–(l) represent 1 cm. All images are acquired in the setup seen in Fig. 1a with the beam incident at an angle of 41°.