Depth-dose

Figure 31 Depth-dose function for electrons in a target of low atomic number. The normalized penetration f = z/Rq.

The depth-dose model allows the gel energy Eg of a resist to be calculated from an observed interface gel dose Dg under conditions of zero backscatter and predicts a dependence of Dg on accelerating voltage going as which agrees reasonably well with experiments. Calculations of... 

Depth-Dose Curve and Energy Loss in Windows... 

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]. 

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

Figure 13 Depth-dose curves for proton beams of different energy. The position of the Bragg peak depends on energy and can thus be adjusted according to the clinical requirements. (From PSI, Villigen, courtesy of Pedroni and Scheib.)...

Figure 14 Proton beam irradiation of a deep-seated large tumor. Single Bragg peaks of different energy are combined, in adequate proportions, to obtain a homogeneous dose distribution at the level of the SOBP. The depth-dose curve of a photon beam, shown for comparison, is inferior compared to the proton curve. However, an optimized multifield photon treatment allows to reach better irradiation conditions. (From Ref 43.)...

The absorption properties of the accelerated electrons in the processed materials are the absorbed dose, the depth dose profile, the penetration range, and the dose rate. 

The depth dose distribution is measured by irradiating a stack of radia-chromic film chips with a thickness slightly greater than the practical range at the energy of interest. The depth dose is determined by evaluating the individual chips. 

BARTLETT, D.T., FRANCIS, T.M. and DIMBYLOW, P.J. (1989). Methodol-ogy for the cahbration of photon personal dosemeters Calculation of phantom backscatter and depth dose distributions, Radiat. Prot. Dosim. 27, 231-244. 

GROSSWENDT, B. and HOHLFELD, K. (1982). Angular dependence of specified depth dose equivalent quantities in the ICRU sphere for photon irradiation, Radiat. FYot. Dosim. 3, 169-174. 

FIGURE 5.2 Depth-dose distribution for electron energies 100-200 keV. (SITA Technology, U.K. With permission.)... 

Using cross plots of the depth-dose curve and 8/So vs. dose (from the nomogram) one can calculate the concentration of contaminants. 

Calculation of G -values from the results shown in Figures 2 and 3 requires determining the amount of dose absorbed in the film for a given incident dose. Bowden (7) has shown, using the depth-dose model of Heidenreich, (9) an accurate measure of the energy absorbed in a polymer film can be determined. An example of such a calculation for polystyrene is given in the appendix. 

Another exposure tool is available in gamma radiation. While the correlation is not always perfect, there is a high degree of similarity in the response of polymers to the radiation from 60Co and from 50 keV electrons. Because of the penetrating nature of gamma rays, the exposure is not restricted to thin films or small amounts of polymer. Also, the absorbed dose is not complicated by the depth-dose function which must be used when electron-... 

For calibrating the accelerator, poly(vinyl chloride) films and a simple water calorimeter are used in addition to monitoring and controlling the electrical parameters of the accelerator which affect the dose output and, in turn, the absorbed dose. The poly(vinyl chloride) is used primarily for establishing the depth dose in samples irradiated with the scanned electron beam. This film is relatively thin when compared with the range of 10... 

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. 

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. 

Figure ll(a,b) shows the distribution of fluence (J cm ) for a broad-beam surface irradiation (where, again, the beam is at least several penetration depths in diameter), for two different cases high absorption relative to scattering (Figure 11(a)) and vice versa (Figure 11(b)). In the former case, the depth dose has a simple exponential form ... 

---