Soutenance de thèse
mardi 30 mars 2021 à 11:00
Arronax (en visio)
Industrial accelerators, performing radioisotope irradiation, rely on a few limited numbers of standard diagnostics to perform their duties. This can restrict precise knowledge of the beam hitting the target. This is a constraint for the facility’s capacity in making the desired beam characteristics but also in dealing with new necessary beam developments.
The work, addressed in the thesis, aims at improving this knowledge and at helping protect the beamline from undesirable events such as high beam losses. With this purpose in view, transverse beam dynamics studies have been carried out both with simulation and experiments with the 70 MeV proton beam available at the Arronax facility - France. The technique employs specifically devised Beam Loss Monitor (BLM) and instrumented four finger collimator typical of radioisotope irradiation end-of-beamlines. The BLM which is a non-destructive ionization chamber based monitor is here detailed before being installed outside the beampipe and used on a regular basis at 150 μA beams.
The results are shown, including various operation conditions particularly in combination with quadrupole gradient modulation techniques. G4Beamline (Geant4 based simulation) has been used to study the beam dynamics in ideal conditions. These studies explored several beam characteristics such as focal point, causes of beam losses, and transverse beam emittance. For further improvement of beam dynamics and future higher intensities operation, a new prototype of beam position monitor (BPM), designed with iThemba labs – S. Africa, has been tested and calibrated with an RF antenna setup replicating a beam which is then also compared with the opera3D simulation. These initial studies indicated that the designed BPM can be used for measuring the beam position at the center (±0.2 mm).
Mots-clés: proton beam, transverse beam dynamics, beam diagnostics, cyclotron