A new energy spectrum reconstruction method for time-of-flight diagnostics of high-energy laser-driven protons.

The Time-of-Flight (TOF) technique coupled with semiconductorlike detectors, as silicon carbide and diamond, is one of the most promising diagnostic methods for high-energy, high repetition rate, laser-accelerated ions allowing a full on-line beam spectral characterization. A new analysis method for reconstructing the energy spectrum of high-energy laser-driven ion beams from TOF signals is hereby presented and discussed. The proposed method takes into account the detector's working principle, through the accurate calculation of the energy loss in the detector active layer, using Monte Carlo simulations. The analysis method was validated against well-established diagnostics, such as the Thomson parabola spectrometer, during an experimental campaign carried out at the Rutherford Appleton Laboratory (UK) with the high-energy laser-driven protons accelerated by the VULCAN Petawatt laser.

Radiobiological quantities in proton-therapy: Estimation and validation using Geant4-based Monte Carlo simulations.

PURPOSE: The Geant4 Monte Carlo simulation toolkit was used to reproduce radiobiological parameters measured by irradiating three different cancerous cell lines with monochromatic and clinical proton beams. METHODS: The experimental set-up adopted for irradiations was fully simulated with a dedicated open-source Geant4 application. Cells survival fractions was calculated coupling the Geant4 simulations with two analytical radiobiological models: one based on the LEM (Local Effect Model) approach and the other on a semi-empirical parameterisation. Results was evaluated and compared with experimental data. RESULTS AND CONCLUSIONS: The results demonstrated the Geant4 ability to reproduce radiobiological quantities for different cell lines.

Transversal dose distribution optimization for laser-accelerated proton beam medical applications by means of Geant4.

The main purpose of this paper is to quantitatively study the possibility of delivering dose distributions of clinical relevance with laser-driven proton beams. A Monte Carlo application has been developed with the Geant4 toolkit, simulating the ELIMED (MEDical and multidisciplinary application at ELI-Beamlines) transport and dosimetry beam line which is being currently installed at the ELI-Beamlines in Prague (CZ). The beam line will be used to perform irradiations for multidisciplinary studies, with the purpose of demonstrating the possible use of optically accelerated ion beams for therapeutic purposes. The ELIMED Geant4-based application, already validated against reference transport codes, accurately simulates each single element of the beam line, necessary to collect the accelerated beams and to select them in energy. Transversal dose distributions at the irradiation point have been studied and optimized to try to quantitatively answer the question if such kind of beam lines, and specifically the systems developed for ELIMED in Prague, will be actually able to transport ion beams not only for multidisciplinary applications, such as pitcher-catcher nuclear reactions (e.g. neutrons), PIXE analysis for cultural heritage and space radiation, but also for delivering dose patterns of clinical relevance in a future perspective of possible medical applications.

A modular Geant4 model of Leksell Gamma Knife Perfexion™.

This work presents a Monte Carlo model of Leksell Gamma Knife Perfexion as well as the main parameters of the dose distribution in the standard phantom obtained using this model. The model is developed in the Geant4 simulation toolkit in a modular way which enables its reuse in other Perfexion studies. Large phase space files were created, containing particles that are entering the inner machine cavity after being transported through the collimation system. All 14 output factors of the machine and effective output factors for both the 4 mm (0.830 ± 0.009) and 8 mm (0.921 ± 0.004) collimators were calculated. Dose profiles along the main axes are also included for each collimator size. All results are compared to the values obtained from the treatment planning system, from experiments, and from other Monte Carlo models.

Event-by-event fluid dynamcis

Coarse grained Langevin-type effective field equations may provide some guidance for the analysis of mesoscopic or microscopic molecular systems exhibiting fluctuations, or for systems of hundreds to thousands of atomic or subatomic particles produced in atomic or high-energy nuclear collisions. Suggestions for consistent realization of random fluctuations in discretized fluid dynamics will be presented.

Addition of CH2O to arginine--a theoretical study by ab initio method.

Arginine is an acid possessing a guanidine side group which is protonated at all biological pHs, R-NH-C(=NH2+)-NH2. We have performed computations on the neutral species by the ab initio method using MINI and 6-31G(d) basis sets. Geometry optimization at the HF SCF level has also been carried out using the 6-31 G(d) basis set. We investigated the addition of formaldehyde to both the NH2- and H-N=C sites of the guanidine side group. The calculated exothermicities of the reactions with formaldehyde were found different for the above structures. We are planning to determine the energy barriers for these reactions in the near future.

Analogies and differences in the excited reactions of formaldehyde and D-glucose.

The investigations proved that D-glucose (as reducing sugar) can easily be activated in a ternary system (L-lysine: D-glucose: H2O2) similarly to formaldehyde at 20 degrees C, in pH = 7.4 forming chemiluminescence (CL) and singlet oxygen. The kinetic investigation showed that: CL lasted many hours (permanent emission) and had no bell-shaped curve differently from other aldehydes e.g. formaldehyde. The reason of the effect is that D-glucose exists mainly in ring form in water solution (Haworth ring form) and the open form (the aldehyde group) is slowly liberated during the excited reaction. These excited reactions may be important in human organism, because D-glucose and lysyl residues of proteins occur permanently in human body and endogenous formaldehyde and H2O2 may be liberated there, too.