Beam Dynamics Characterization of the IFMIF/EVEDA RFQ Input Beam

The high intensity accelerators are one of the world-wide leading edge research in the beam dynamics studies. The upgrades of the existing accelerator LINAC4, FERMILAB, FAIR and the new applications on the neutron technologies such as ESS, IFMIF, MUNES, both for science research, medical treatment and material testing require an increase knowledge in the high intensity beams treatment. One of the most difficult part to be treated and which represent the first obstacle in increasing the beam intensity in the accelerators, is the injector part: the large number of charge particles at low energy forms a strongly interacting system, subjected to the Coulombian interaction. The situation further complicates due to the presence of different species which produces a plasma-like behavior of the beam. On the behalf of the INFN-LNL team, I participated to the commissioning of the high intensity injector (source and low energy transfer line) of the IFMIF/EVEDA project. Via experiments and simulation model developments I contributed to the study of the beam behavior in this specific framework. In particular I upgrade the emittance measurement routine in order to manage correctly the artifacts; I develop and benchmark with measurements self-consistent simulation models of the LEBT and extraction transfer line, which includes the secondary electron from residual gas and from metal due to collisions; I design a modification of medium and high energy line in order to test the CW steady state of the longest radio frequency quadrupole in the world, an in-kind contribution of INFN. All the development routines and experience will give important contributions for the next high intensity facilities. The first chapter presents the motivation of the IFMIF project and the main characteristics required by the accelerator. The main challenges of such accelerator are also listed. The second chapter introduces the main concepts of the beam dynamics of space-charge which will be used in the thesis. The third chapter presents the IFMIF/EVEDA project, with a description of the main elements; particular focus is made onto the source, the low energy beam transfer line and on the radio frequency quadrupole. Scaling law derivation for the extracted beam with contaminants is shown. The commissioning phases are introduced, each with its specific challenges. The fourth chapter presents the modification of the emittance analysis routine which can manage the ghost infested signal of the IFMIF/EVEDA emittancemeter. The fifth and the sixth chapters contains the simulation models developed to estimate the space-charge beam behavior under neutralization regime: the model with constant neutralization and the one with the full secondary plasma evolution are presented and benchmarked with the measurements. In the fifth chapter the measurements refers to 60−55 mA proton beam at 50 keV, while for the sixth chapter the beam considered is composed of 140−135 mA deuteron beam at 100 keV. In these chapters, the variation of the radio frequency quadrupole beam input characteristics with respect to the electromagnetic plasma confinement of the low energy transfer line is studied. The original contribution in these simulations is given by the emitted secondary electron from metal, which as some effects on the space charge compensation process, on the emittance value. Deep study of the multispecies distributions and behavior was performed. The four chapter defines, for the experimental proton point considered, the solenoid variations where searching the maximum radio frequency quadrupole transmission. The output beam behavior of this one is studied in commissioning perspective. In thesixth chapter, after testing the radio frequency quadrupole transmission with the secondary plasma model (also said dynamic neutralization model) with a realistic beam distribution, the simulations of the extraction system are presented. The benchmark with the measurements are also performed. The seventh chapter presents the design of the modification of the medium and high energy transfer sections of the accelerator in order to allow the test of the CW of the radio frequency quadrupole, bypassing the superconductive cavities. Extensive simulations of the system robustness to the errors are explored. The last chapter reports the conclusions.