No abstract

FLASH radiotherapy is a novel radiation delivery modality, generally considered a potential breakthrough in cancer care. With ultra-high dose rates (>40 Gy/s) delivered in fractions of a second, FLASH is characterized by unique irradiation conditions which bring along new challenges in dosimetry and beam monitoring. This article reports on the validation of innovative detection systems based on sub-millimeter-sized fast scintillation detectors coupled to optical fibers. We characterized different scintillators, namely Gadolinium Aluminium Gallium Garnet (GAGG), yttrium doped barium fluoride (Y-BaF2), and polystyrene, by studying their response to ultra-high dose rate 18 MeV proton beams. Beam tests were carried out at the Bern medical cyclotron, providing beams for multidisciplinary research activities and commercial radioisotope production, that we characterized for ultra-high dose rates irradiations. The possibility of changing the scintillator to be coupled to the optical fiber gives great flexibility to the system, by allowing to measure proton dose rates up 10.4 kGy/s and mm-small fields with high time resolution. The measurements reported in this paper were performed at a sampling rate of 20 kHz, although data acquisition up to 10 MHz is possible. The developed detection system can be successfully used to measure ultra-high dose rates and it can be further optimized to address specific and essential issues of FLASH radiation therapy, including quality assurance, real-time beam monitoring and in-vivo dosimetry.

No abstract

We report on a search for axion-like dark matter using a Ramsey-type apparatus for cold neutrons. A hypothetical axion-gluon-coupling would manifest in a neutron electric dipole moment signal oscillating in time. Twenty-four hours of data have been analyzed in a frequency range from 23 µHz to 1 kHz, and no significant oscillating signal has been found. The usage of present axion and darkmatter models allowed excluding the coupling of axions to gluons in the mass range from 1.5 × 10 −20 to 6.6 × 10 −13 eV with a best sensitivity of CG/fama = (3.1 ± 0.2) × 10 12 GeV −2 (95% C.L.).

No abstract