A detector based on silica fibers for ion beam monitoring in a wide current range

Abstract

A: A detector based on doped silica and optical fibers was developed to monitor the profile of particle accelerator beams of intensity ranging from 1 pA to tens of µA. Scintillation light produced in a fiber moving across the beam is measured, giving information on its position, shape and intensity. The detector was tested with a continuous proton beam at the 18 MeV Bern medical cyclotron used for radioisotope production and multi-disciplinary research. For currents from 1 pA to 20 µA, Ce 3+ and Sb 3+ doped silica fibers were used as sensors. Read-out systems based on photodiodes, photomultipliers and solid state photomultipliers were employed. Profiles down to the pA range were measured with this method for the first time. For currents ranging from 1 pA to 3 µA, the integral of the profile was found to be linear with respect to the beam current, which can be measured by this detector with an accuracy of ∼1%. The profile was determined with a spatial resolution of 0.25 mm. For currents ranging from 5 µA to 20 µA, thermal effects affect light yield and transmission, causing distortions of the profile and limitations in monitoring capabilities. For currents higher than ∼1 µA, non-doped optical fibers for both producing and transporting scintillation light were also successfully employed. K: Beam-line instrumentation (beam position and profile monitors; beam-intensity monitors; bunch length monitors); Instrumentation for particle accelerators and storage rings -low energy (linear accelerators, cyclotrons, electrostatic accelerators); Instrumentation for particle-beam therapy 1Corresponding author.

A system for online beam emittance measurements and proton beam characterization

“…This tool is essential for the optimization of the beams employed in the ongoing research activities. The 4 PrOBεaM system can be deployed for similar measurements at other accelerator facilities. Further optimizations of the system, including simultaneous beam scanning in both planes are ongoing, and its commercialization is planned.…”

“…The corresponding beam profiles at a distance of 694 mm from the quadrupole were measured with the UniBEaM detector for each magnet setting. The second technique was the use of multiple beam profilers, for which the 4 PrOBεaM system was again used. During the measurements of the transverse beam emittance, the cyclotron parameters were kept constant and set to the standard values.…”

Study of the Extracted Beam Energy as a Function of Operational Parameters of a Medical Cyclotron

“…As shown in Figure 5, the resonance plateau may shift of a few per mille to higher values of the current in the main coil. The beam intensity was evaluated by the integral of the beam profile measured by the UniBEaM [13]. The carousel for the beam extraction was set at an angle of θ = 97.08 • and the extraction foil 2 was used.…”

“…To assess the deflection angle, a beam profile detector was located downstream the dipole at 63 cm from the centre of the magnet. A specific detector named UniBEaM [13] was designed and constructed to fit an ISO-K 100 flange. It is based on a Ce-doped silica fibre that is moved across the beam by means of a high-precision motor.…”

Nuclear physics experiments with a medical cyclotron

“…It is used for two main scientific activities: 3 1) production of the 18 F radioisotope for Positron Emission Tomography (PET) imaging and 2) research activities focused on the production of new radioisotopes 4 and on studies of new beam monitoring and diagnostics systems, new detectors and dosimeters. [5][6][7] Research activities at Bern medical cyclotron are possible thanks to a specifically designed Beam Transfer Line (BTL). 8 Recently, owing to an increasing interest of the scientific community in the availability of well characterized neutron beams, 9 we started a project aiming at upgrading the Bern medical cyclotron as a neutron source, mainly for studies of radiation hardness and for tests of new neutron detectors.…”