Ionoacoustics for three-dimensional particle bunch monitoring

Gerlach, Sonja (2023): Ionoacoustics for three-dimensional particle bunch monitoring. Dissertation, LMU München: Fakultät für Physik

Abstract

Ionoacoustics refers to the measurement of acoustic waves excited by ions as they slow down in matter. One particularly interesting application is the monitoring of individual laser-accelerated ion bunches, which challenges many established online detection systems. The ionoacoustic approach offers advantages in this context. It is resistant to the strong electromagnetic pulse emitted during the laser-plasma interaction, and it does not exhibit saturation even at very high particle fluxes. Recovering the Ion-Bunch Energy distribution from a recorded Acoustic Trace (I-BEAT) has conceptually been proven. This work introduces two new detector designs, the I-BEAT 3D and the TI-BEAT detector, and develops a fast analysis routine based on an analytical model. The result is a novel and versatile online detector for short and intense ion bunches that enables immediate feedback. Describing the dose deposition of protons in matter, particularly in the entrance window and the water reservoir of the detector, connects the most important proton bunch parameters to the resulting ionoacoustic signals and hence serves for the development of a simple and fast data analysis method for particle bunches with Gaussian energy spectra and lateral distributions. This is key to the analysis and interpretation of the acoustic traces obtained with the detector designs. The I-BEAT 3D detector uses four transducers and is studied in experiments at two laser-driven proton beamlines located at CALA and the HZDR. Via the new analytical model, it provides the mean bunch energy, energy spread and lateral bunch position of individual bunches in less than one second. Additionally, the detector allows the monitoring of relative changes in lateral bunch size. Experiments with proton bunches at kinetic energies between 10 MeV and 30 MeV reveal sub-MeV and sub-mm resolution. Cross-calibration using radiochromic films proves that the new methodology can determine the absolute number of particles contained in a single bunch with uncertainties of only 10%. The TI-BEAT detector uses a short water reservoir to allow ions with sufficient energy to pass through. It is developed to prove that ionoacoustics can also function as transmission monitor for particle bunches. The detector concept is evaluated at the GSI’s SIS-18 synchrotron with xenon ions at kinetic energies of 385 MeV/u. The precision of determining the absolute lateral position and relative changes in the lateral size of ion bunches is 0.15 mm and less than 0.1 mm, respectively. The particle number is extracted with a precision between 4% and 8%. The new detector designs and the data evaluation method provide a fast, compact, cost-effective and electromagnetic pulse-resistant online tool for monitoring important ion bunch parameters at application sites. This provides the foundation for irradiation studies and can serve as feedback for automated optimization of laser-driven proton sources.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Ionoacoustics, Laser-ion sources, Diagnostics
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 530 Physik
• Fakultäten: Fakultät für Physik
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 13. November 2023
• 1. Bericht­erstatter:in: Schreiber, Jörg