Backscattering factor

Excitation by Electrons. A portion of the electrons impinging on a phosphor are backscattered elastically with loss of energy. The backscattering factor r and the averaged atomic number Z of the atoms are related by [5.308]... 

Figure 8,15 The source backing material backscatters particles and necessitates the use of a backscattering factor /. ...

To correct properly for this effect, a source backscattering factor (/ ) is defined by... 

The backscattering factor is important, in most cases, only for charged particles. It depends on three variables ... 

Figure 8.16 (a) The backscattering factor /j as a function of thickness b of the backing material, (b) The saturation backscattering factor as a function of the atomic number Z of the backing material. 

The dependence of the saturation backscattering factor of electrons on the kinetic energy and the atomic number of the backing material is given by the following empirical equation, based on a least-squares fit of experimental results ... 

Figure 8.17 Backscattering factor as a function of energy for C, Al, Cu, and Au. Curves were obtained using Eq. 8.16.

A thick backing material is used, for which the saturation backscattering factor should be employed for correction of the data. 

For accurate results, the backscattering factor should be measured for the actual geometry of the experiment. 

How would the result of Prob. 8.9 change if the backscattering factor was known with an error of +1 percent, the efficiency with an error of +0.5 percent, and the source self-absorption factor with an error of 1 percent ... 

A point isotropic source is located at the center of a hemispherical 2tr counter. The efficiency of this detector tor the particles emitted by the source is 85 percent. The saturation backscattering factor is 1.5. The background is 25 + 1 counts/min. What is the strength of the source if 3000 counts are recorded in 1 min What is the standard error of this measurement ... 

A plastic scintillation detector was to be calibrated for absolute measurements of /3-radiation. For this purpose a 2.13 X 10 M TlCl3 solution was available with a specific activity of 13.93 iCi ml T1 emits iS-particles with 0.77 MeV. Of this solution 0.1 ml is evaporated over an area of exactly 0.1 cm on a platinum foil. The sample is counted in an evacuated vessel at a distaiKe of 15.3 cm from the detector, which has a sensitive area of 1.72 cm. The detector registers 2052 cpm with a background of 6 cpm. What is (a) the surface weight of the sample, (b) the backscattering factor, and (c) the detector efficiency for the particular /3 s ... 

The new factor in Equation (8) compared to that for XPS is the backscattering factor r - ICHi-MURA and Shimizu [132] have carried out extensive Monte Carlo calculations of the backscatter-... 

The backscattering factor, /-m, is obtained from the parametric fits to the results of Monte Carlo calculations by Ichimura and Shimizu [531 given by Shimizu [54] for the angles of incidence of 0° (normal incidence). 30° and 45° ... 

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