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We investigated the radiation-induced luminescence of cerium- and nitrogen-doped optical fibers at high dose rates (>40 Gy(H2O)/s) using high-energy proton beams (19–73 MeV) at flux and fluences representative of FLASH radiotherapy treatments. For each fiber material, we evaluated the dosimetry performances of both pristine (not irradiated) and preirradiated samples to study the effect of an X-ray pretreatment, up to a dose of 260 kGy. The core sizes of 50 $\mu $ m for the Ce-doped fiber and 62.5 $\mu $ m for the N-doped one offer exploitability in terms of spatially resolved dosimetry for proton therapy beams. We also improved the fiber dosimetry calibration running Geant4 and SRIM simulations to obtain the conversion factors between the dose rate values, usually given in water, and those for our silica-based samples. The two fibers exhibit promising features since with only one calibration, we can obtain information about the dose rate and the dose at the same time, due to the same fiber sensitivity to both quantities. Finally, we checked the sensors response for different proton energies, obtaining a less than 15% dispersion for the Ce-doped fiber sensitivity from 19 to 73 MeV. For very high dose rate applications, the preirradiated Ce-doped optical fiber shows the most promising characteristics.

We investigated the potential of an optical material (Ce-doped silica rod of ~0.5 mm in diameter and ~1 cm in length) developed by a sol–gel process to perform in situ proton beam profile measurement through the monitoring of its visible radioluminescence (RIL) features peaking around 480 nm. Various test configurations (collimator sizes and varying distances from the collimators) have been performed to assess the sensor performances at the TRIUMF facility in Vancouver offering a 63-MeV proton beam. The obtained results are promising, showing their potential to characterize the flux and beam profile at this facility offering radiation testing capabilities or medical treatments. The reported performances could be improved by pre-irradiating the probe sample to reduce the observed slight bright burn effect on the quality of the profile measurements. These results open the way to most advanced sensors’ architecture such as ribbons of optical fibers drawn from this sol–gel rod, to acquire in one step the complete beam profile.

Magneto optical traps (MOT) allow the cooling and storing of neutral atoms in a volume of a few cubic millimeters by use of laser beams and a magnetic field. Such devices offer new and exciting opportunities for precision measurements of radioactive isotopes. Here we present experiments performed with a double-MOT system coupled to the on-line separator TISOL at TRIUMF/Vancouver, Canada. For the first time, the Β-decay of free atoms stored in such a device could be observed. We report on coincidence measurements between beta-particles and the argon recoils in the decay of 37K and 38rm{m}}K. The charge state ratios of the recoil-ions were deduced by Time-Of-Flight separation in an acceleration field. The final goal of those investigations is a precision test of the Standard Model by measuring the –nu-correlation parameter a.