Speaker
Description
Ultra-short and ultra-intense pulsed lasers allow for accelerating short bunches of protons and ions to MeV-range energies. Our aim is to design and build an experimental setup for the L2A2 laboratory, at the University of Santiago de Compostela, for the study of radiobiological effects caused by laser-accelerated protons on human cancer cell cultures. The Ti:Sapphire laser at L2A2 delivers 1.2 J pulses at a rate of 10 Hz and peak power of 50 TW. The corresponding focused intensity is sufficient for accelerating protons to 5-10 MeV through the Target Normal Sheath Acceleration mechanism (TNSA).
The beam of accelerated protons/ions passes through a pinhole collimator followed by a sequence of permanent magnets that generate a configuration of antiparallel magnetic fields with the purpose of bending the trajectories of the protons and separating them from electrons and photons originating from the laser-plasma interaction. In addition, the magnetic fields act as an energy separator with a resulting, lateral displacement of the protons depending on their momentum. This allows for selecting a narrow range of energies with approximately uniform dose deposition within the irradiated area. This entire setup is located inside a vacuum chamber. The particles leave the chamber through a thin foil of kapton (polyimide) and finally impinge on the cell culture outside the vacuum system. Cell cultures are prepared and analysed at the Fundación Pública Galega Medicina Xenómica and IDIS. The first trials will be centred around the quantification of DNA double-strand breaks as a function of radiation dose.
A major challenge of this project is the precise measurement of the dose deposited by the laser-driven beams. For significant doses (up to 5 Gy), several shots have to be accumulated. Shot-to-shot fluctuations of the proton flux impose the necessity for online monitoring which is demanding in our range of energies. Furthermore, the response of electronic detectors to ultra-high instantaneous rates will be studied in careful cross-calibration measurements with passive materials. The experiment is under construction and it is planned to be running in 2021.
