Ponente
Descripción
During recent years the relevance of dose rate, in addition to total dose, has been recognized to understand the response of biological systems to ionizing radiation. Particle sources based on ultra-intense laser-plasma interactions offer unique conditions to apply instantaneous dose rates orders of magnitude larger than classical accelerators. We present an ongoing research program on radiation effects of laser-generated X-rays and protons on living cells.
A stabilized X-ray source has been realised at the Laser Laboratory for Acceleration and Applications (L2A2, Santiago de Compostela). A 30 fs pulsed laser with 1 mJ beam energy at 1 kHz shot rate is focalized on a rotating copper plate. It generates a bremsstrahlung spectrum at low X-ray energies (up to some tens of keV). This source has been used to apply a total dose of 3-8 Gy to 36 monolayer cell cultures of a human adenocarcinoma (A549) which were prepared at the close-by Instituto de Investigación Sanitaria (IDIS). At 10 cm target distance the irradiation time per sample is about 30-120 s. The applied dose is measured with radiochromic film. In addition, an ionization chamber has been implemented for real-time control.
Our first experiment on biological effects of laser-accelerated protons has been recently run at Centro de Láseres Pulsados (CLPU, Salamanca). A three-axis controlled wheel, developed by IGFAE, has been applied for the precise positioning of 808 individual targets per vacuum cycle in the focal spot of the VEGA-3 laser (1 PW, 27 J at 1 Hz pulse rate). A magnetic energy selector, developed by i3M and previously tested at the 18 MeV cyclotron of Centro Nacional de Aceleradores (CNA, Sevilla), has been implemented to obtain a quasi-monoenergetic proton beam which was conducted through a thin vacuum window. A total of 27 cell samples, prepared by Instituto de Biología Funcional y Genómica (IBFG), have been exposed to tens of nanosecond proton pulses accumulating total dose values between 3 and 8 Gy.
In addition to first results we will highlight the manyfold, technological and logistic challenges of the two experimental campaigns which, on the national level, have been the first combining laser-particle sources with biological sample manipulation. The aim of our research program is to compare the cellular effects of ultra-short, pulsed sources from high-power laser-plasma interactions with continuous beam facilities such as clinical linacs, proton therapy centers, or external accelerator beamlines.
The authors would like to thank the Spanish Center of Pulsed Lasers (CLPU) and the members of the Consortium (Central Government, Regional Government of Castilla y Léon and Universidad de Salamanca) for considering experiment 00562-0101 as a strategic proposal that develops new potentialities for CLPU and, therefore, finance the access to its facilities, as well as to acknowledge the results obtained with its petawatt laser t system (VEGA-3) and its scientific and technical assistance. Supported by the Government of Castilla y León under the project CLP263P20 “Transport and manipulation of particles in laser accelerators: New scenarios in flash radiotherapy (TYMPAL), co-financed with FEDER funds. i3M received funding by Generalitat Valenciana, ref. CIAICO/2022/008 and EDGJID/2021/204.
