PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika
PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika
PROCEEDINGS OF THE 7 INTERNATIONAL ... - Fizika
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I. Cibulskaite et al. / Medical Physics in the Baltic States 7 (2009) 72 - 75<br />
Table 2 Scatter dose in planar Si volume<br />
Scatter dose, Gy (mA s) -1<br />
Construction<br />
25 kV 28 kV 30 kV<br />
0.1 mm Si, 1,258*10<br />
without coating<br />
-<br />
1,236*10<br />
12<br />
-<br />
1,356*10<br />
12<br />
-<br />
12<br />
0.1 mm Si with 1,259*10<br />
0.001 mm SiO2<br />
coating<br />
-<br />
1,239*10<br />
12<br />
-<br />
1,359*10<br />
12<br />
-<br />
12<br />
0.1 mm Si with 1,260*10<br />
0.001 mm<br />
a-C:H coating<br />
-<br />
1,238*10<br />
12<br />
-<br />
1,361*10<br />
12<br />
-<br />
12<br />
0.1 mm Si with 1,260*10<br />
0.001mm<br />
carbon coating,<br />
containing SiOx<br />
-<br />
1,238*10<br />
12<br />
-<br />
1,360*10<br />
12<br />
-<br />
12<br />
0.1mm Si with 1,272*10<br />
0.1 mm carbon<br />
coating,<br />
containing SiOx<br />
-<br />
1,288*10<br />
12<br />
-<br />
1,413*10<br />
12<br />
-<br />
12<br />
However these coatings also have to provide almost the<br />
same or better protective properties as the often used<br />
relative thick free standing polymeric foils do.<br />
4. Conclusions<br />
The calculation of the total and scatter doses in Si<br />
samples coated by protective coatings were performed<br />
using Monte Carlo based modeling code EGSnrc. The<br />
modeling of (25-32) keV the X-ray photons interaction<br />
processes with mentioned material allowed to<br />
investigate the scatter contribution to the registered dose<br />
thought obtained total and scatted doses results. The<br />
75<br />
criterion of the scatter contribution is scatter to total<br />
dose ratio. Combination of the scatter modelling results<br />
obtained from Monte Carlo calculations with the<br />
manufacturing technological parameters of the<br />
experimental coatings, allows to get coatings that have<br />
good protective features, with possibly low scatter dose<br />
to total dose ratio and in this way to optimise the<br />
construction of ionising radiation detector that are<br />
suitable for low energy X-ray photon doses recording.<br />
As the modelling results shows, the influence of the thin<br />
(< 1 μm) DLC coatings containing SiOx , to X-ray<br />
scattering processes within detector material was<br />
negligible.<br />
5. References<br />
1. Kawrakow I.; Rogers D.W.O. The EGSnrc<br />
Code System. Monte Carlo Simulation of Electron and<br />
Photon Transport. National Reasearch Council of<br />
Canada. 2003. http://www.irs.inms.nrc.ca<br />
2. Rogers D.W.O., Kawrakow I., Seuntjens J.P.,<br />
Walters B.R.B., Mainegra-Hing E. NRC User Codes for<br />
EGSnrc. NRCC Report PIRS-702, 2005.<br />
3. Dosimetric Aspects of Mammography. Report<br />
6 of the Netherlands Commission on Radiation<br />
Dosimetry, 1993.<br />
4. Cranley B. J. Gilmore, G. W. A. Fogarty, and<br />
L. Desponds, IPEM Report 78. Catalogue of Diagnostic<br />
X-Ray Spectra and other Data. The Institute of Physics<br />
and Engineering in Medicine IPEM; CD-Rom Edition<br />
1997. Electronic Version prepared by D. Suttond, 1997.