In clinical diagnostic measurements Free-Air-Chambers (FAC) is heavily used. However, due to the air inside the detector and several other factors the Dose, the quantity of interest, has to be corrected from the measurement. In the past these several correction factors have been obtained by direct/indirect measurements or by simulations. Here we wanted to reevaluate results from simulations carried out back in the early 2000s and if necessary to correct them. To achieve this new simulations using MCNP have been carried out. To seperate all the contributions to the different correction factors it is necessary to analyze the track of each particle individually and therefore I developed a program called "PTRAC-Analyzer" which analyzes PTRAC-Files generated by MCNP and from this calculates the specific correction factors.
This project has been very similar to the previous one, but with completely different motivations. The aim here was to calculate back the real emitted spectra by X-Ray tubes used in clinical diagnostic measurements from the measured spectra. Again the same problems as for Gamma Ray spectra arise when measuring them. Therefore, low energetic photon transport simulations in air have been carried out using again the Monte-Carlo transport Code "MCNP" for different detector types (e.g. HPGe-Detectors).
As a side product of this project I also developed a Graphical User Interface for the people at Seibersdorf Laboratories, to calculate the real X-Ray spectra for measured spectra and different detector geometries.
As already mentioned in About me, this project has been my Bachelor Thesis carried out in cooperation with Seibersdorf Laboratories. The aim was to improve the Signal-to-Background ratio of a Portal monitor (a radiation detector used mainly at junkyards) by using different lead-shieldings in somewhere around the detecting volume. Since these shieldings are not cheap to produce, we used Monte-Carlo simulations to simulate the detection process and from those results decide which shielding types to produce. Therefore the Monte-Carlo transport code "MCNP" has been used.
The deconvolution of Gamma Ray spectra was necessary to implement a realistic Background measurement into the simulations, since the spectrum measured by a detector is not the real emitted spectrum by the radiation source due to physical processes in- and outside the detector (e.g. backscattering processes).
Bernd RiedererInstitut für Physik