Ponente
Descripción
In recent years, there has been a growing interest in laser-driven ion accelerators as a potential alternative to conventional accelerators for certain applications [1], mainly because of their smaller footprint and cost-effectiveness. A particularly promising application is the production of radionuclides of interest for medical imaging and therapy, via nuclear reactions such as $^{11}$B(p,n)$^{11}$C [1,2,3]. Typically, the production of these radionuclides is centralised at large cyclotrons, which reduces the number of facilities required, but limits the range of usable radionuclides to those with longer lifetimes [2]. For this reason, laser-driven accelerators could be an interesting option for in-situ generation of short-lived isotopes [2], such as $^{11}$C, which is valuable for PET medical imaging but currently restricted in use due to its short lifetime ($t_{1/2}$= 20.36 min).
However, techniques such as PET imaging require activities in the range of 10 – 30 MBq for preclinical, and between 200 MBq and 1 GBq for clinical imaging, above those that can be produced in a single irradiation by ion beams driven by commercial laser systems, but potentially achievable by the continuous irradiation of an activation sample. For this purpose, a rotating wheel developed in-house at L2A2 allowing for multi-Hz operation [4]. A modified version of this target, allocating up to 808 shots, has been successfully deployed at a recent experiment at CLPU (Spain), where protons with energy in excess of 12 MeV were obtained, using 200 fs pulses with energies of up to 30 J focused down to 18 μm of spot size. The accelerated protons were used to produce $^{11}$C in a proof-of-principle experiment. This was achieved via the aforementioned $^{11}$B(p,n)$^{11}$C nuclear reaction by placing a boron disk close to the interaction point. A diagnostic based on the use of two CsI detectors operating in coincidence was developed to measure in-vacuum the activity generated in the sample. A total activity above 230 kBq was measured from a burst of only 20 shots at 0.1 Hz, giving activities greater than 12 kBq/shot. These results indicate that pre-clinical activities are already achievable under the current conditions with extended irradiation times. Furthermore, in order to reach higher activities, additional developments towards a system capable of producing thousands of shots at 10 Hz will be presented.
[1] Z. Sun, AIP Advances 11, 040701 (2021).
[2] S. Fritzler et al., Appl. Phys. Lett. 83, 3039 (2003).
[3] H. Daido et al., Rep. Prog. Phys. 75, 056401 (2012).
[4] J. Peñas et al. Submitted HPLSE 2023.
