Printz Ringbaek T.,Mittelhessen University of Applied Sciences |
Printz Ringbaek T.,University of Marburg |
Printz Ringbaek T.,Aarhus University Hospital |
Simeonov Y.,Mittelhessen University of Applied Sciences |
And 7 more authors.
Physics in Medicine and Biology | Year: 2017
Porous materials with microscopic structures like foam, sponges, lung tissues and lung substitute materials have particular characteristics, which differ from those of solid materials. Ion beams passing through porous materials show much stronger energy straggling than expected for non-porous solid materials of the same thickness. This effect depends on the microscopic fine structure, the density and the thickness of the porous material. The beam-modulating effect from a porous plate enlarges the Bragg peak, yielding similar benefits in irradiation time reduction as a ripple filter. A porous plate can additionally function as a range shifter, which since a higher energy can be selected for the same penetration depth in the body reduces the scattering at the beam line and therefore improves the lateral fall-off. Bragg curve measurements of ion beams passing through different porous materials have been performed in order to determine the beam modulation effect of each. A mathematical model describing the correlation between the mean material density, the porous pore structure size and the strength of the modulation has been developed and a new material parameter called 'modulation power' is defined as the square of the Gaussian sigma divided by the mean water-equivalent thickness of the porous absorber. Monte Carlo simulations have been performed in order to validate the model and to investigate the Bragg peak enlargement, the scattering effects of porosity and the lateral beam width at the end of the beam range. The porosity is found to only influence the lateral scattering in a negligible way. As an example of a practical application, it is found that a 20 mm and 50 mm plate of Gammex LN300 performs similar to a 3 mm and 6 mm ripple filter, respectively, and at the same time can improve the sharpness of the lateral beam due to its multifunctionality as a ripple filter and a range shifter. © 2017 Institute of Physics and Engineering in Medicine.
Krantz C.,Max Planck Institute for Nuclear Physics |
Krantz C.,Marburg Ion Beam Therapy Center |
Badnell N.R.,University of Strathclyde |
Muller A.,Justus Liebig University |
And 2 more authors.
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2017
We review experimental and theoretical efforts aimed at a detailed understanding of the recombination of electrons with highly charged tungsten ions characterised by an open 4f sub-shell. Highly charged tungsten occurs as a plasma contaminant in ITER-like tokamak experiments, where it acts as an unwanted cooling agent. Modelling of the charge state populations in a plasma requires reliable thermal rate coefficients for charge-changing electron collisions. The electron recombination of medium-charged tungsten species with open 4f sub-shells is especially challenging to compute reliably. Storage-ring experiments have been conducted that yielded recombination rate coefficients at high energy resolution and well-understood systematics. Significant deviations compared to simplified, but prevalent, computational models have been found. A new class of ab initio numerical calculations has been developed that provides reliable predictions of the total plasma recombination rate coefficients for these ions. © 2017 IOP Publishing Ltd.
Scheeler U.,Marburg Ion Beam Therapy Center |
Krantz C.,Marburg Ion Beam Therapy Center |
Sievers S.,Marburg Ion Beam Therapy Center |
Strohmeier M.,Marburg Ion Beam Therapy Center |
And 10 more authors.
IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference | Year: 2016
The Marburg Ion-Beam Therapy Centre (MIT), located in Marburg, Germany, is in clinical operation since 2015. MIT is designed for precision cancer treatment using beams of protons or carbon nuclei, employing the raster scanning technique. The accelerator facility consists of a linacsynchrotron combination, developed by Siemens Healthcare/Danfysik, that was in a state of permanent stand-by upon purchase. With support from its Heidelberg-based sister facility HIT, the MIT operation company (MIT Betriebs GmbH) recommissioned the machine in only 13 months, reaching clinical standards of beam quality delivered to all four beam outlets. With the first medical treatment in October 2015, MIT became the third operational hadron beam therapy centre in Europe offering both proton and carbon beams. Copyright © 2016 CC-BY-3.0 and by the respective authors.