We have developed a model for proton depth dose and lateral distributions based on Monte Carlo calculations (GEANT4) and an integration procedure of Bethe-Bloch equation (BBE). The model accounts for the transport of primary and secondary protons, the creation of recoil protons and heavy recoil nuclei as well as lateral scattering of these contributions. The buildup, which is experimentally observed in higher energy depth dose curves, is modeled by an inclusion of two different origins: (1) secondary reaction protons with a contribution of ca. 65% of the buildup (for monoenergetic protons). (2) Landau tails as well as Gaussian type of fluctuations for range straggling effects. All parameters of the model for initially monoenergetic proton beams have been obtained from Monte Carlo calculations or checked by them. Furthermore, there are a few parameters, which can be obtained by fitting the model to the measured depth dose curves in order to describe individual characteristics of the beamline—the most important being the initial energy spread. We find that the free parameters of the depth dose model can be predicted for any intermediate energy from a couple of measured curves.

CdTe solar cells and modules have been manufactured on polyimide (PI) substrates. Aluminum doped zinc oxide (ZnO:Al) was used as a transparent conductive oxide (TCO) front contact, while a thin high resistive transparent layer of intrinsic zinc oxide (i-ZnO) was used between the front contact and the CdS layer. The CdS and CdTe layers were evaporated onto the ZnO:Al/i-ZnO coated PI films in a high vacuum evaporation system followed by a CdCl(2) activation treatment and a Cu-Au electrical back contact deposition. In some cases prior to the cell deposition, the PI film was coated with MgF(2) on the light facing side and the effects on the optical and electrical properties of TCO and solar cells were investigated. The limitations on current density of solar cells due to optical losses in the PI substrate were estimated and compared to the experimentally achieved values. Flexible CdTe solar cells of highest efficiencies of 12.4% and 12.7% were achieved with and without anti-reflection MgF(2) coating, respectively.Laser scribing was used for patterning of layers and monolithically interconnected flexible solar modules exhibiting 8.0% total area efficiency on 31.9 cm(2) were developed by interconnection of 11 solar cells in series. (C) 2010 Elsevier B.V. All rights reserved.

We have developed a model for proton depth dose and lateral distributions based on Monte Carlo calculations (GEANT4) and an integration procedure of the Bethe-Bloch equation (BBE). The model accounts for the transport of primary and secondary protons, the creation of recoil protons and heavy recoil nuclei as well as lateral scattering of these contributions. The buildup, which is experimentally observed in higher energy depth dose curves, is modeled by inclusion of two different origins: 1. Secondary reaction protons with a contribution of ca. 65 % of the buildup (for monoenergetic protons). 2. Landau tails as well as Gaussian type of fluctuations for range straggling effects. All parameters of the model for initially monoenergetic proton beams have been obtained from Monte Carlo calculations or checked by them. Furthermore, there are a few parameters, which can be obtained by fitting the model to measured depth dose curves in order to describe individual characteristics of the beamline - the most important being the initial energy spread. We find that the free parameters of the depth dose model can be predicted for any intermediate energy from a couple of measured curves.

Purpose: Collimator scatter of proton beams is being implemented in the proton dose model in ECLIPSE (Varian). Due to the energy loss and angular scatter distributions at the collimator walls (brass) the spectrum of scatter protons is rather intricate. This contribution is significant for the ‘horns’ of transverse profiles verified in the initial plateau of Bragg curves. Using an analytical integration procedure of Bethe‐Bloch equation and its application to the Molière multiple scatter model the calculated contributions are compared with measured data and Monte‐Carlo calculations (GEANT4). The production of secondary protons and radiation effects is determined by an integration of the inelastic cross‐section of the corresponding wall material over the energy. Method and Materials: Monte‐Carlo calculations have been carried out with GEANT4. Measurement data of transverse profiles and Bragg curves have been made available by the Harvard cyclotron and the proton center of MD Anderson (Houston). Results: Material properties and collimator length have an influence to the beam‐line (energy spectrum, fluence, angular distribution). Since the collimator edge act as further proton source, the distance to the water tank significantly affects the Bragg curves of small field sizes (from 0.5 × 0.5 cm2 to 2 × 2 cm2). For larger field sizes the collimator scatter leads to ‘horns’ in the transverse profiles and to a buildup effect in the initial plateau of Bragg curves. Conclusion: Monte‐Carlo and analytical calculations are in good agreement with measurement data. A practical impact is also application of proton beams to the stereotactic radiotherapy. Conflict of Interest: Varian Medical Systems.

Purpose: To develop a fast Monte Carlo (MC) dose engine for proton radiation treatment planning calculations and research studies. Method and Materials: We developed a complete MC simulation system for calculating the dose distributions in patients. The system uses a commercial treatment planning system with an analytical dose algorithm to design the treatment plans. A DICOM‐RT‐ION interface was developed to allow automated data transfer between the treatment planning system and the MC system. The MC model included all major components of a passively‐scattered proton treatment unit and a CT‐based patient model. A suite of programs converted the prescriptive data (e.g., range, modulation width, field size) and patient CT data into a MC input file, including coordinate system transformations for arbitrary treatment beam orientations. The radiation transport calculations are performed with the MCNPX Monte Carlo system running on a cluster of 512 64‐bit CPUs. For each treatment field, multiple simulation output files were postprocessed and the resulting MC dose matrix was written to the DICOM‐RT‐ION plan. The plan was then imported into the commercial planning system for visualization. Results: The MC simulations and pencil beam dose distributions are in good agreement for a two‐field prostate plan and a three‐field lung plan. The prostate plan required 1.6 hours and the lung plan required 14 hours using 512 CPUs to achieve < 2 % statistical uncertainty in the total dose at isocenter. The computing time was directly related to the number of voxels in the patient model. Timing studies revealed that the simulation speed for this system scales almost linearly with the inverse number of CPUs. Conclusion: The results of this study strongly suggest that it is feasible to implement a fast and easy‐to‐use MC treatment planning dose engine with currently available computing technologies and resources.

Purpose: An improved version of the spot/raster scanning algorithm is being implemented in the proton dose model in ECLIPSE (Varian). Since the beam-line of this treatment modality is rather different from other modalities using wheels and nozzles, measured Bragg curves also significantly differ in the initial plateau, resulting from an energy spectrum with a manifest Landau tail, if the initial proton energy is E ⩾ 140 MeV (in particular, if E ⩾ 200 MeV). Method and Materials: Proton Bragg curves have been delivered by different vendors and therapy centers, which show a significant buildup effect in the plateau region. The computational procedure is based on an analytical integration of Bethe-Bloch equation and on the inelastic cross-section of oxygen and some other materials (the transport of secondary protons is rigorously accounted for). The energy/range straggling of proton pencil beams used in scanning methods is described by a generalization of the composite Gaussian convolution kernel containing Landau tails in dependence of the energy (analytical representation of a Vavilov distribution function). Results: The experimental data obtained by scanning methods can excellently be explained by the generalized convolution model, which is only a composite Gaussian convolution for proton energies E ⩽ 140 MeV. The buildup effect in the initial plateau region is accurately described. Proton beam-lines using range shifters provide Bragg curves with only very small indication of buildup effects, if E ⩾ 200 MeV. Conclusion: An accurate description of Bragg curves including buildup effects is an important feature of therapy planning systems, since the calculation of SOBP and monitor units (MU, absolute dosimetry) are incorrectly described by fitting curves neglecting Landau tails. Conflict of Interest: Varian Medical Systems.

An analytical integration of Bethe-Bloch equation is presented to provide the energy E(z) as a function of z and dE/dz. Together with multiple scatter the influence of collimators to depth dose curves and a profile is studied and compared with GEANT4.

Purpose: To configure and test a treatment planning system (TPS) (Varian, Palo Alto) for use with a passively‐scattered proton therapy delivery system. Methods and Materials: Since the mechanical designs of the commercial beam delivery apparatus (Probeat, Hitachi Limited, Japan) had not yet been completed, measurements of the required data were not possible. Instead, we designed our own therapy system components using analytical methods. The MCNPX (Los Alamos National Laboratory) Monte Carlo (MC) code was used to simulate beam profiles. Separate codes were developed to create the initial proton sources, the absorbed dose and fluence tallies, and simple homogeneous water phantoms (see Zheng et al., separate contribution). Up to 108 proton histories were tracked per simulation to achieve < 2% statistical uncertainties. Additional codes were developed to generate ancillary TPS configuration files, e.g., for the range modulator wheels, flattening filters, and variable range shifter. The MC beam characteristics such as penetration range were compared with values from independent one‐dimensional analytical calculations. Results: A complete set of configuration parameters and beam profiles were generated, including 832 dose and fluence profiles, in approximately four weeks (simulation time using 60 CPUs). With the simulated configuration data, the TPS has undergone extensive development and testing during the past year. Preliminary results indicate that the MC, TPS, and independent analytical calculations are in good agreement (< 4 mm differences in penetration range). Conclusion: The results of this study demonstrate the practicality of MC models to calculate beam data for configuring a proton treatment planning system. Additional simulations with the manufacturer's preliminary equipment designs are now in progress. Validation tests of Eclipse in heterogeneous media are in progress (see Titt et al., separate contribution). Confirmatory measurements are planned. Conflict of Interest: This work was funded in part by a research grant from Varian.

Lesbians, gays, and bisexuals (LGBs) are far more likely than heterosexuals to support the Democratic Party and its candidates. But is this support due to the Democratic Party support for the civil rights agendas of historically disadvantaged groups, or is it based on other factors? In this article, we use the issue of same-sex marriage to attempt to explain the nature of the sexual identity gap. We demonstrate that a substantial portion of LGBs place a great deal of importance on winning healthcare and other employee benefits for their spouses, but that they are less concerned about having legally recognized marriages. Furthermore, we find that it is the goal of acquiring spousal benefits, not the right to marry, that influences the degree to which LGBs support the Democratic Party We conclude that the sexual identity gap is generated more from LGB concerns about acquiring tangible economic benefits than from an interest in pursuing civil rights.

A novel high-temperature solar chemical reactor is proposed for the thermal recycling of hazardous solid waste material using concentrated solar power. It features two cavities in series, with the inner one functioning as the solar absorber and the outer one functioning as the reaction chamber. The solar reactor can handle thermochemical processes at temperatures above 1,300 K involving multiphases and controlled atmospheres. It further allows for batch or continuous mode of operation and for easy adjustment of the residence time of the reactants to match the kinetics of the reaction. A 10-kW solar reactor prototype was designed and tested for the carbothermic reduction of electric arc furnace dusts (EAFD). The reactor was subjected to mean solar flux intensities of 2,000 kW m(-2) and operated in both batch and continuous mode within the temperature range of 1,120-1,400 K. Extraction of over 90% of the toxic compounds originally contained in the EAFD was achieved while the condensable products of the off-gas contained mainly Zn, Pb, and Cl. The use of concentrated solar energy as the source of process heat offers the possibility of converting hazardous solid waste material into valuable commodities for processes in closed and sustainable material cycles.

The thermochemical conversion and recycling of hazardous solid waste materials is investigated using high-temperature solar process heat. Electric arc furnace dust (EAFD), an important source of waste contaminated with heavy metals, is being considered. The chemical equilibrium composition and the energy required to process it, using carbon as reducing agent, is computed for temperatures in the range 300– 2000 K. Zinc, lead and iron can be extracted from their oxides in reducing atmospheres at above 1300 K. The thermal energy requirement for converting EAFD at 1500 K is 3000 kJ/kg, and the solar exergy conversion efficiency can be as high as 67%. Major sources of irreversibilities are those associated with the re-radiation losses of the solar reactor and the heat rejected during the quenching. The use of concentrated solar energy as the source of process heat avoids emissions of greenhouse gases and other pollutants derived from the combustion of fossil fuels, and further offers the possibility of converting waste materials into valuable commodities for processes in closed and sustainable materials cycles.

The broad-beam three-dimensional irradiation system under development at National Institute of Radiological Sciences (NIRS) requires a small ridge filter to spread the initially monoenergetic heavy-ion beam to a small spread-out Bragg peak (SOBP). A large SOBP covering the target volume is then achieved by a superposition of differently weighted and displaced small SOBPs. Two approaches were studied for the definition of a suitable ridge filter and experimental verifications were performed. Both approaches show a good agreement between the calculated and measured dose and lead to a good homogeneity of the biological dose in the target. However, the ridge filter design that produces a Gaussian-shaped spectrum of the particle ranges was found to be more robust to small errors and uncertainties in the beam application. Furthermore, an optimization procedure for two fields was applied to compensate for the missing dose from the fragmentation tail for the case of a simple-geometry target. The optimized biological dose distributions show that a very good homogeneity is achievable in the target.

A two-dimensionally position sensitive dosimetry system has been tested for different dosimetric applications in a radiation therapy facility with a scanning proton beam. The system consists of a scintillating (fluorescent) screen, mounted at the beam-exit side of a phantom and it is observed by a charge coupled device (CCD) camera. The observed light distribution at the screen is equivalent to the two-dimensional (2D)-dose distribution at the screen position. It has been found that the dosimetric properties of the system, measured in a scanning proton beam, are equal to those measured in a proton beam broadened by a scattering system. Measurements of the transversal dose distribution of a single pencil beam are consistent with dose measurements as well as with dose calculations in clinically relevant fields made with multiple pencil beams. Measurements of inhomogeneous dose distributions have shown to be of sufficient accuracy to be suitable for the verification of dose calculation algorithms. The good sensitivity and sub-mm spatial resolution of the system allows for the detection of deviations of a few percent in dose from the expected (intended or calculated) dose distribution. Its dosimetric properties and the immediate availability of the data make this device a useful tool in the quality control of scanning proton beams.

The thermochemical conversion and recycling of hazardous solid waste materials is investigated using high-temperature solar process heat. Two important sources of wastes contaminated with heavy metal oxides are considered: (1) electric are furnace dust (EAFD) and (2) automobile shredder residue (ASR). The chemical equilibrium composition of these complex materials and the energy required to process them, using carbon, methane, or pyre-coke as reducing agents, are computed for temperatures in the range 300-2000 K. Metals can be extracted from their oxides in reducing atmospheres at above 1300 K for both EAFD and ASR: Zn is obtained in the gas phase, while Fe, Pb, and Cu are obtained in the condensed phase. The thermal energy requirements for converting EAFD at 1500 K are 3008 kJ/ kg and 4143 kJ/kg using C(gr) and CH4 as reducing agents, respectively. For converting ASR at 1500 K, 2455 kJ/kg are required. The solar exergy conversion efficiency, i.e., the efficiency of converting solar energy into the chemical energy of the reaction products (given by the Gibbs free energy change of product oxidation), can be as high as 69% for the EAFD conversion and 87% for the ASR conversion. Major sources of irreversibilities are those associated with the reradiation losses of the solar reactor and the heat rejected during the quenching. The use of concentrated solar energy as the source of process heat avoids emissions of greenhouse gases and other pollutants derived from the combustion of fossil fuels and further offers the possibility of converting waste materials into valuable commodities for processes in closed and sustainable materials cycles.

The gantry for proton radiotherapy at the Paul Scherrer Institute (PSI) is designed specifically for the spot-scanning technique. Use of this technique to its full potential requires dose calculation algorithms which are capable of precisely simulating each scanned beam individually. Different specialized analytical dose calculations have been developed, which attempt to model the effects of density heterogeneities in the patient's body on the dose. Their accuracy has been evaluated by a comparison with Monte Carlo calculated dose distributions in the case of a simple geometrical density interface parallel to the beam and typical anatomical situations. A specialized ray casting model which takes range dilution effects (broadening of the spectrum of proton ranges) into account has been found to produce results of good accuracy. This algorithm can easily be implemented in the iterative optimization procedure used for the calculation of the optimal contribution of each individual scanned pencil beam. In most cases an elemental pencil beam dose calculation has been found to be most accurate. Due to the long computing time, this model is currently used only after the optimization procedure as an alternative method of calculating the dose.

Bei der 5-Felder-Technik zur Bestrahlung des Mammakarzinoms werden mehrere aneinandergrenzende Felder verwendet. Dies sowie die oberflächennahe Lage des Tumors können in der Bestrahlungsplanung erhebliche Probleme verursachen. In der vorliegenden Arbeit wird eine solche Bestrahlung in einem homogenen Phantom mit Hilfe der Filmdosimetrie verifiziert. Es zeigt sich, daß kleine Ungenauigkeiten des Dosismodells entlang der Feldränder beträchtliche Fehler zur Folge haben können, wenn zwei aneinandergrenzende Felder berechnet werden (< 7 %). Ebenfalls gut zu erkennen ist eine Überschätzung der Dosis in oberflächennahen Bereichen, da der Verlust von Phantomstreuung nicht richtig wiedergegeben wird (< 8 %). In bestimmten Bereichen des Bestrahlungsvolumens können sich allerdings beide Effekte addieren und zu Dosisabweichungen bis zu 15 % führen. Die Methode der Filmdosimetrie hat sich für die vorliegende Fragestellung bewährt. Bei sorgfältiger Kalibrierung lassen sich nicht nur relative, sondern auch absolute Dosisverteilungen mit guter Präzision messen.