Electron depth-dose curve

The dose distribution in the materials is given as a depth-dose curve. An example of the curve is illustrated in Fig. 4 obtained with the irradiation of electron from 0.5 to 1.0 MeV using cellulose triacetate (CTA) film dosimeter [12]. The existence of the maximum dose is an important characteristic of the depth-dose curve. Irradiation from two opposite sides by using two accelerators was proposed in order to give better uniformity in water [13]. The uniform irradiation is also important for flue gas treatment. Better efficiency of NO removal was proved with both-side irradiation by using three accelerators for coal-fired flue gas than single-side irradiation at the same dose [14]. 

ZAGORSKI, Z.P. Dependence of depth-dose curves on the energy spectrum of 5 to 13 MeV electron beams , Radiat.Phys.Chem 22 (1983) 409-418. 

Calorimeters can be used as in-house standards for the calibration of other dosimeters. It is crucial to pay special attention to the irradiation geometry to ensure the same dose to the calorimeter and to the dosimeter being irradiated. The thickness of the calorimeter (i.e., the absorber) must be chosen so that, for unidirectional perpendicular electron beams, the absorbed dose measurement is the average dose on the ascending part of the depth-dose curve. Phantoms of, e.g., polystyrene have been built of similar size as the water, graphite, or polystyrene calorimeters allowing the secondary dosimeter to be placed at depths of interest to provide the same irradiation conditions both for the absorber and the reference or routine dosimeter. 

Figure 4 Depth-dose distribution curves in CTA stack films with the irradiation of electron. (From Ref. 11.)...

The X-ray depth dose distributions in a thick water absorber with large area beams are shown in Fig. 3. These distributions indicate that the attenuation is essentially exponential, and that the penetrating quality increases with the incident electron energy. Depth dose distributions for irradiating materials from opposite directions show the minimum dose in the middle of the material. The dose uniformity ratio (DUR), also known as the Dmax/Dmin dose ratio, increases with the thickness of the material, as shown in Fig. 4 (lower set of curves). For any thickness, the DUR decreases as the incident electron energy increases. 

In the ultraviolet spectrum of polyethylene taken at 77 °K. after an irradiation to a dose of 40 Mrads there is also a broad absorption band in the region of 310 m/x to be seen. This is shown more clearly in Figure 3 in terms of a plot of the difference in the absorbance between Curve 1 of Figure 2 and curve 2. Actually the A A values of Figure 3 were not calculated from curves 1 and 2 of Figure 2, but from similar curves observed in another experiment. It is unlikely that the 310 m/x band can be attributed to trapped electrons because the energy of this band, 4.0 e.v., is much greater than the depth of electron traps in polyethylene,... 

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