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International audience; We investigated the potential of a multimode (50 μ m core diameter) nitrogen doped silica-based optical fiber for X-rays, protons and γ-rays radiation detection and dosimetry. X-rays results confirm that this N-doped fiber presents a strong radioluminescence (RL) around 550 nm when exposed to radiation. The RL observed from a few cm long sample linearly depends on the dose rate at least in the 1 mGy/s to 50 Gy/s range. Low dose rate γ-ray tests demonstrate the radiation detection at dose rate as low as 40 μ Gy/s with a 2 m long fiber sample. This fiber is also associated with an optically-stimulated luminescence (OSL) when exposed to a 1064 nm laser light post-irradiation. This OSL signature provides shortly after the irradiation a precise estimation of the accumulated dose at least in the 1 Gy to 10 kGy range. Under proton exposure, we benchmarked the performances of the N-doped fiber with the ones of a conventional Markus chamber used by the TRIUMF proton-therapy team. This comparison highlights the potential of the small-size N-doped fiber to partially overcome the known limitations of commercial fiber-based dosimeters for medical applications. The obtained results are very promising for the future design of more complex spatially-resolved beam monitoring systems.

International audience; We investigated the radioluminescence and optically-stimulated luminescence properties of a 50μm core diameter N-doped fiber. This fiber provides precise dose rate and dose measurements and very promising characteristics for protontherapy beam dosimetry.

International audience

International audience; We developed fs-fiber Bragg gratings resistant to ionizing radiations (X or gamma-rays). We demonstrated here the robustness of this sensor technology to proton fluences representative of the most challenging space missions

International audience; We demonstrate the potential of sol-gel silica fiber materials doped with copper and cerium ions to monitor the proton flux and fluences through radiation-induced luminescence and optically stimulated luminescence techniques.

Introduction Monte-Carlo simulations can be used to assess isotope production on small medical cyclotrons. These simulations calculate the particle interactions with electric and magnetic fields, as well as the nuclear reactions. The results can be used to predict both yields and isotopic contaminations and can aid in the optimum design of target material and target geometry [1,2]. FLUKA is a general-purpose tool widely used in many applications from accelerator shielding to target design, calorimetry, activation, dosimetry, detector design, neutrino physics, or radiotherapy [3,4]. In this work, we applied the Monte-Carlo code FLUKA to determine the accuracy of predicting yields of various isotopes as compared to experimental yields. Material and Methods The proton beam collimation system, as well as the liquid and solid target of the TR13 cyclotron at TRIUMF, has been modeled in FLUKA. The proton beam parameters were initially taken from the cyclotron design specifications and were optimized against experimental measurements from the TR13. Data from irradiations of different targets and with different beam currents were collected in order to account for average behavior, see FIG. 1. Yields for a pencil proton beam as well as a beam spread out in direction and energy have been calculated and have been compared to experimental results obtained with the TR13. Results and Conclusion The reactions listed in TABLE 1 were assessed. For most reactions a good agreement was found in the comparison between experimental and simulated saturation yield. TABLE 1 only shows the yields simulated with a proton beam with a spread in both direction and energy. In most cases, the simulated yield is slightly larger or comparable. Only the calculated yield for 55Co was significantly lower by a factor of 4.2. This is still a good agreement considering that FLUKA was originally a high-energy physics code. It may indicate that the FLUKA internal cross-section calculation for this isotope production needs some optimization. In summary, we conclude that FLUKA can be used as a tool for the prediction of isotope production as well as for target design.

International audience

Active targets are perfect tools for the study of reactions induced by radioactive ion beams of very low intensity. Thus, they make possible the study of direct and compound reactions at the same time. In this talk, we will present the results obtained with the MAYA active target for low energy reactions induced by the halo nucleus 11Li. A method used to measure the mass of short-lived nuclei, applied to the 11Li case will be discussed. The experimantal angular distribution of the two halo-neutron transfer reaction 1H(11Li,9Li)t at 4.3A MeV, using the MAYA detector as a thin target, will be presented and compared to coupled reaction channel calculations including 3-body models in order to extract informations on the structure of the 11Li halo. The extraction of the 11Li+p optical potential using the data on the elastic scattering, will also be discussed. Finally, the excitation function of the resonant elastic scattering reaction, determined using the MAYA detector as a thick target, will be presented. Extraction of information on the structure of possible 12Li isobaric analog states observed in 12Be using several R-matrix calculations will be shown.

Active target MAYA, expérience TRIUMF; The mass of 11Li has been determined from Q-value measurements of the 1H(11Li, 9Li)3H reaction. The experiment was performed at TRIUMF laboratory with the GANIL active target MAYA. Energy-energy and angle-angle kinematics reconstruction give a Q value of 8.119(22) MeV for the reaction. The derived 11Li two-neutron separation energy is S2n = 363(22) keV.

The heavy-ion radiative capture reaction, 12C(12C,$\gamma$), has been investigated at energies both on- and off-resonance, with a particular focus on known resonances at Ec.m.=6.0, 6.8, 7.5, and 8.0 MeV. Gamma rays detected in a BGO scintillator array were recorded in coincidence with 24Mg residues at the focal plane of the DRAGON recoil separator at TRIUMF. In this manner, the relative strength of all decay pathways through excited states up to the particle threshold could be examined for the first time. Isovector M1 transitions are found to be a important component of the radiative capture from the Ec.m.=6.0 and 6.8 MeV resonances. Comparison with Monte Carlo simulations suggests that these resonances may have either J=0 or 2, with a preference for J=2. The higher energy resonances at Ec.m.=7.5 and 8.0 MeV have a rather different decay pattern. The former is a clear candidate for a J=4 resonance, whereas the latter has a dominant J=4 character superposed on a J=2 resonant component underneath. The relationship between these resonances and the well-known quasimolecular resonances as well as resonances in breakup and electrofission of 24Mg into two 12C nuclei are discussed.

The photorecombination of highly charged few-electron mercury ions Hg75+ to Hg78+ has been explored with the Heidelberg electron beam ion trap. By monitoring the emitted x rays (65–76 keV) and scanning the electron beam energy (45–54 keV) over the KLL dielectronic recombination (DR) region, the energies of state-selected DR resonances were determined to within ±4 eV (relative) and ±14 eV (absolute). At this level of experimental accuracy, it becomes possible to make a detailed comparison to various theoretical approaches and methods, all of which include quantum electrodynamic (QED) effects and finite nuclear size contributions (for a 1s electron, these effects can be as large as 160 and 50 eV, respectively). In He-like Hg78+, a good agreement between the experimental results and the calculations has been found. However, for the capture into Li-, Be-, and B-like ions, significant discrepancies have been observed for specific levels. The discrepancies suggest the need for further theoretical and experimental studies with other heavy ions along these isoelectronic sequences.

We have set limits on contributions of scalar interactions to nuclear beta decay. A magneto-optical trap (MOT) provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and be detected in coincidence with the beta. This allows reconstruction of the neutrino momentum, and the measurement of the beta-neutrino correlation, in a more direct fashion than previously possible. The beta-neutrino correlation parameter of the 0+ to 0+ pure Fermi decay of 38mK is $\tilde{a}$=0.9981+-0.0030+-0.0037, consistent with the standard model prediction a=1., 4 pages, 3 figures, accepted by Phys. Rev. Lett., centroid changed

A laser ion source (LIS) has been designed and successfully tested for loading the Heidelberg electron beam ion trap (H-EBIT) with ions of practically all solid-state elements. A pulsed YAG:Nd3þ laser (30 mJ, 8 ns) is used to produce plasma from a solid target. Lowly charged ions are extracted from the plasma and accelerated by a short high-voltage pulse, generating a pulsed ion beam with energy of up to 6 keV per charge. The ion beam is transported into the EBIT, decelerated and captured within it by switching the trapping electrode potentials. The electron beam further ionizes the trapped ions to the desired highly charged states. The experimental setup is described together with the source parameters measured for different target materials. X-ray spectra of up to He-like highly charged ions (Cu, Mo, Pb, Al and Ge) produced in the EBIT after injection from the LIS have been measured. The reliability and convenience of this method allows the use of the LIS to produce highly charged ions of both insulating and conducting solid elements with an EBIT as needed for different experiments.