A Fast and Universal Vlasov Solver for Beam Dynamics Simulations in 3D
The Vlasov equation can describe the evolution of a particle density under the effects of electromagnetic fields and thus it is possible to describe the evolution of a charged particle beam within an accelerator beam line. The Vlasov equation forms a partial differential equation in a 6D phase space witch renders it very expensive if it is solved via classical methods. A more efficient approach consists in representing the particle distribution function by a discrete set of characteristic moments. For each moment a time evolution equation can be stated. These ordinary differential equations can then be integrated efficiently by means of numerical methods if all acting forces together with a proper initial condition are given. The beam dynamics simulation tool V-Code has been implemented at TEMF on the basis of the moment approach. In this paper the numerical model, main features and designated use cases of the V-Code will be presented.
MOMENT-BASED SIMULATION OF THE S-DALINAC RECIRCULATIONS ∗
In this paper an outline of the numerical model and the implementation of the moment-based beam dynamics sim- ulation tool V-Code is presented together with new sim- ulation results regarding the S-DALINAC recirculations. These simulations demonstrate the applicability of the V- Code to properly reproduce the recirculating layout includ- ing the longitudinal beam dynamics within the dispersive sections. So far, the acceleration of the particles within the main linac section is done on crest of the accelerating electric field of the 8 superconducting cavities. Together with an isochronous recirculation scheme, were every particle has the same revolution time L independent of its energy, the field errors coherently add up throughout the three main linac passages. This results in a undesired increase of the energy spread. In order to reduce the energy spread caused by the ob- served phase- and amplitude-jitters a new non-isochronous recirculation scheme is currently being investigated at the IKP. This scheme utilizes longitudinal dispersion DL in the recirculation paths together with an off-crest acceleration as it is done for example in microtrons. The intended longitudinal dispersion leads to the fact that particles with higher energy re-enter the LINAC earlier, whereas particles with lower energy re-enter the LINAC later. In (1) a phase shift of 7.5 degree and a longitudinal dispersion of -1.5 mm/% were found to be an optimal working point for the two S-DALINAC recirculations. Under these conditions the effects of the phase- and amplitude jitters on the energy spread can almost be compensated.
Techno-economic analysis of solar thermal power plants using liquid sodium as heat transfer fluid
Abstract Solar thermal power plants with central receiver and thermal storage are expected to be one key technology in future electricity generation, because they are renewable and due to the thermal storage independent of the current solar radiation. State-of-the-art solar power plants often use molten nitrate salts as heat transfer fluid. The use of liquid sodium instead leads to lower electricity generation costs. Sodium has a high thermal conductivity and thus large heat transfer rates are possible. Hence, a smaller absorber surface is sufficient for the same thermal power. As a result, the sodium receiver achieves a higher efficiency at lower investment cost. Additionally, the aiming strategy, which reduces the peak heat flux on molten salt receivers isn’t necessary for sodium. Even at high heat flux densities, the absorber tubes will be cooled sufficiently due to the high heat transfer coefficients. Therefore, the sodium receiver in this analysis is designed for one single aim point, resulting in a heat flux density of q mean = 1.06 MW / m 2 and q peak = 2.99 MW / m 2 . The state-of-the-art system with molten salt considers q mean = 0.51 MW / m 2 and q peak = 1.0 MW / m 2 . The presented techno-economic analysis of two sodium based concepts compared to a reference system with molten salt results in up to 16% lower electricity generation costs.