280642 research outputs found
Sort by
Experimental assessment of novel PET detector components for online imaging of radioactive ion beams
No full textObjective.This work aims to evaluate the ability of novel detector components to measure with submillimeter resolution in beam positron emission tomography (PET) signals produced by10C and11C radioactive ion beams stopped in PMMA targets and to validate a simulation toolkit for reproducing beam physics and PET detector responses within the framework of the biomedical applications of radioactive ion beam (BARB) project.Approach.The PET system response was assessed by visualizing the radioactive distributions of the beams stopped in tissue surrogate phantoms, and the capacity of the simulation toolkit was evaluated by comparing the experimental results with simulations, both for the depth-dose distribution and PET imaging.Main results.The detector assembly accurately visualized the PET signal with submillimeter resolution, achieving the objective of measuring the difference in the positron range between10C and11C. The simulation toolkit effectively reproduced the beam characteristics and detector responses, showing a high degree of agreement between the simulated and experimental PET profiles under different beam delivery conditions.Significance.These findings demonstrate the precision and reliability of the novel in-beam PET detector technology and simulation toolkit for small animals, establishing a solid foundation for the second phase of the BARB project, which involves preclinical irradiation of living mice
Deceleration of ion beams - Related challenges and opportunities
No full textThe GSI facilities of CRYRING and HiTRAP are used for decelerating ion beams to low energies. This deceleration phase is preceded by the generation and acceleration of those ions. CRYRING and HiTRAP operate at the junction between accelerator science and atomic physics. The scientfic motivation, the operation principle, the state of the art and future outlooks are presented
Numerical simulations of binary neutron star merger ejecta
No full textImproving numerical simulations of binary neutron star mergers (BNSM) is essential for advancing our understanding of and ability to interpret observations of these events. We demonstrate that smoothed particle hydrodynamic simulations of BNSM yield differing outcomes for identical merger events. This thesis is the first study to explore these variations, considering the possibility that they may be physical stochastic effects arising from small initial perturbations. We perform simulations of a 1.35-1.35 solar mass binary system with the same physical and numerical setup and discuss the observed variation in ejecta properties and the post-merger gravitational wave signal. We find an antiproportional correlation between the ejecta mass and the amplitude of the main feature fₚₑₐₖ of the gravitational wave frequency spectrum. We show that these fluctuations depend on how the double core structure evolves after merging. Our simulations do not yield a reduction of these variations when increasing the resolution, which might be an indication that these fluctuations are a physical effect. To make reliable predictions for the electromagnetic signal of merger events, it is necessary to evolve the mass-outflows on timescales which are significantly longer than the merger itself. Over this time, the ejecta dilutes and cools down over several orders of magnitude. We present a method to extend tabulated equation of states (EoS) to encompass lower rest-mass densities and temperatures. We investigate the issue that outflowing matter evolve towards negative internal energies in regions of low resolution in our simulations. We improve the discretization of the general-relativistic energy evolution equation to reduce the occurrence of this issue. Utilizing the extended EoS and the improved discretization of the energy equation, we perform a long-term BNSM simulation up to 250 milliseconds after merger. We estimate how much material reaches homologous expansion within this time. Our analysis indicates that the majority of the material expelled during the first 25 milliseconds nearly exhibits homologous expansion, and we estimate an upper bound of 10 % for the alteration in its radial velocity. For later ejecta, we observe that they attain a reduced velocity, requiring a duration on the order of seconds to reach homologous expansion. BNSM simulations of this length require a sufficient resolution of the expanding ejecta. We present a method to efficiently increase the resolution of BNSM ejecta in smoothed particle hydrodynamic simulations. We implement particle splitting, test different splitting criteria, and conduct a comparative study between simulations with and without particle splitting. Our findings indicate that the resolution of the BNSM ejecta can be enhanced by a factor of five using our proposed method while maintaining similar computational expenses
